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1
Lin, Feng Ying. "Smoothed particle hydrodynamics". Mémoire, Université de Sherbrooke, 2005. http://savoirs.usherbrooke.ca/handle/11143/4654.
Testo completoAbstract (sommario):
Since its introduction in the late 1970s by Lucy [11] and Gingold and Monaghan [4], smoothed particle hydrodynamics (SPH) has been used in many areas. It has grown into a widely-recognized technique with many practical applications. In this thesis, we present a new application of the SPH method: a new algorithm for computing a null divergence velocity field using SPH for incompressible flow - a pure SPH solution of the Helmholtz-Hodge decomposition. Also, a new version of the Laplacian for SPH is proposed and the advantages and disadvantages of different gradient and Laplacian approximation formulas used in SPH are also discussed. A new treatment of boundary conditions is proposed for the whole solution procedure. Throughout the thesis, a brief historical overview is presented, along with some fundamental notions about SPH and computational fluid dynamics.
2
Akinci, Nadir [Verfasser], e Matthias [Akademischer Betreuer] Teschner. "Interface handling in smoothed particle hydrodynamics = Interface-Handhabung in Smoothed Particle Hydrodynamics". Freiburg : Universität, 2014. http://d-nb.info/1114829331/34.
Testo completo
3
Galagali, Nikhil. "Algorithms for particle remeshing applied to smoothed particle hydrodynamics". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55074.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 57-59).
This thesis outlines adaptivity schemes for particle-based methods for the simulation of nearly incompressible fluid flows. As with the remeshing schemes used in mesh and grid-based methods, there is a need to use localized refinement in particle methods to reduce computational costs. Various forms of particle refinement have been proposed for particle-based methods such as Smoothed Particle Hydrodynamics (SPH). However, none of the techniques that exist currently are able to retain the original degree of randomness among particles. Existing methods reinitialize particle positions on a regular grid. Using such a method for region localized refinement can lead to discontinuities at the interfaces between refined and unrefined particle domains. In turn, this can produce inaccurate results or solution divergence. This thesis outlines the development of new localized refinement algorithms that are capable of retaining the initial randomness of the particles, thus eliminating transition zone discontinuities. The algorithms were tested through SPH simulations of Couette Flow and Poiseuille Flow with spatially varying particle spacing. The determined velocity profiles agree well with theoretical results. In addition, the algorithms were also tested on a flow past a cylinder problem, but with a complete domain remeshing. The original and the remeshed particle distributions showed similar velocity profiles. The algorithms can be extended to 3-D flows with few changes, and allow the simulation of multi-scale flows at reduced computational costs.
by Nikhil Galagali.
S.M.
4
Vijaykumar, Adithya. "Smoothed Particle Hydrodynamics Simulation for Continuous Casting". Thesis, KTH, Matematik (Inst.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-105554.
Testo completoAbstract (sommario):
This thesis proposes a way of simulating the continuous casting process of steel using Smoothed Particle Hydrodynamics (SPH). It deals with the SPH modeling of mass, momentum and the energy equations. The interpolation kernel functions required for the SPH modeling of these equations are calculated. Solidification is modeled by some particles are used to represent fluids and others solids. Elastic forces are calculated between the particle neighbors to create deformable bodies. The fluid solidifies into the elastic body when it cools down and the elastic body melts as it is heated. In continuous casting the molten metal solidifies forming a shell when it comes in contact with the cold wall. The mold of the continuous casting is modeled with a cold oscillating wall and a symmetric wall. Once the shell is formed water is sprayed on the solidified metal. If the shell is thin and cooling is not sufficient, the elastic body melts due to the effect of the hot fluid.Den klassiska SPH-modellen för vätskor med fri yta kompletteras med värmeledning med fasomvandling och stelning: partiklar kan byta mellan vätske-tillstånd och solid-tillstånd beroende på temperaturen. Elastiska krafter beroende på avstånd mellan partiklarna aktiveras i solid-tillståndet och slås av i fluid-tillstånd så att vätskan kan stelna och senare smälta igen om så behövs. Vid stränggjutning stelnar smältan, som fylls på via ett rör, vid kontakt med en oscillerande, kall kokill-vägg, till ett elastiskt skal. Detta kyls fortlöpande genom påsprutning av vatten utanpå kokillen och direkt på skalet, som förångas. Skalet deformeras nedanför kokillen av det hydrostatiska trycket från smältan; om det ar för tunt brister det. Som demonstration gjordes en simulering där ett skal skapas, varpå man slår av vattenkylningen på ett parti: då smälter skalet och blir tunnare och till sist brister det och all smälta rinner ut genom hålet. Noggrannheten i simuleringen lämnar en del att önska men det vore mycket svårt att bygga en så komplex modell med vanlig CFD.
5
McCabe, Christopher. "Smoothed particle hydrodynamics on graphics processing units". Thesis, Manchester Metropolitan University, 2012. http://e-space.mmu.ac.uk/304852/.
Testo completoAbstract (sommario):
A recent development in Computational Fluid Dynamics (CFD) has been the meshless method calledWeakly Compressible Smoothed Particle Hydrodynamics (WCSPH), which is a Lagrangian method that tracks physical quantities of a fluid as it moves in time and space. One disadvantage of WCSPH is the small time steps required due to the use of the weakly compressible Tait equation of state, so large scale simulations using WCSPH have so far been rare and only performed on very expensive CPU-based supercomputers. As CFD simulations grow larger and more detailed, the need to use high performance computing also grows. There is therefore great interest in any computer technology that can provide the equivalent computational power of the CPU-based supercomputer for a fraction of the cost. Hence the excitement aroused in the SPH community by the Graphics Processing Unit (GPU). The GPU offers great potential for providing significant increases in computational performance due to its much smaller size and power consumption relative to the more established and traditional high performance computers comprising hundreds or thousands of CPUs. However, there are some disadvantages in programming GPUs. The memory structure of the GPU is more complex and more variable in speed, and there are other factors that can seriously affect performance, such as the thread grid dimensions which drives the occupancy of the GPU. The aim of this thesis is to describe how WCSPH can be efficiently implemented on multiple GPUs. First, some CFD methods and their success or otherwise in simulating free surfaces are discussed, and examples of previous attempts at implementing CFD algorithms on GPUs are given. The mathematical theory of WCSPH is then presented, followed by a detailed examination of the architecture of a GPU and how to program a GPU. Two different implementations of the same WCSPH algorithm are then described to simulate a well known experiment of a collapse of a column of water to highlight two possible uses of the GPU memory. The first method uses the fast shared memory of the GPU, which is recommended by the GPU manufacturer, while the second method uses the texture i memory of the GPU, which acts as a cache. It is shown that due to the theory of WCSPH, which allows particles to only interact with other particles a short distance apart, that despite the speed of the shared memory and the power of coalescing data into the shared memory, the texture memory method is currently the most efficient, but that this method of implementing WCSPH on a single GPU requires a much higher degree of complexity of programming than the shared memory method. It is also shown that the size of the thread block can have a significant effect on performance. Riemann solvers add more computational effort but can provide more accuracy. The use of Riemann solvers in WCSPH and their success or otherwise is then examined, and the results and performance of one particular WCSPH algorithm that uses an approximate Riemann solver when executed on a GPU are reported. The treatment of boundaries has been and continues to be a problem in WCSPH, and there are a number of creative proposals for boundary treatments. Some of these are described in detail before a new boundary treatment is proposed that builds upon a boundary treatment that was recently proposed, and improves its performance in execution time on a GPU by using the registers and not the slower memories of the GPU. This new boundary treatment builds a unique private grid of boundary particles for each fluid particle close to the boundary. All computation is performed in the registers, the properties of the boundary particles depend on the fluid particle only, and there is no requirement to recall data from the slower global or texture memories of the GPU. The new boundary treatment is also shown to propagate a solitary wave further, preserves the wave height more and takes less execution time to compute than the original boundary treatment this new treatment builds on. A unique and simple implementation of WCSPH on multiple GPUs is then described, and the results of a simulation of a collapse of a column of water in 3D are reported and compared against the results from a simulation of the same problem with the same WCSPH algorithm executed on a large cluster of multi core CPUs. The conclusion is that simulations on a small cluster of GPUs can achieve greater performance than from a cluster of multi core CPUs, but to achieve this the slow GPU memories, including the texture ii memory, must be avoided by using the registers as much as possible, and the architecture of the network linking the GPUs together must be exploited. The former was achieved by using the new boundary treatment proposed in this thesis and discussed above, and the latter was achieved by the use of the MPI Group functionality. The GPUs used for this thesis were already connected together in boxes of 4 by the manufacturer. The cluster used for this thesis consisted of 8 of these boxes, giving a total of 32 GPUs. These boxes of 4 GPUs were connected together through a common host, but the communication speed over the connection between the box and the host is much slower than that between the GPUs inside the box. The total communication time was minimized by grouping the GPUs inside a box together with their private unique MPI communicator, and a communication procedure was created to minimize communication over the relatively slow connection between the boxes of GPUs and the host. Finally, some conclusions are drawn and suggestions for further work are made.
6
Ismail, Ernesto Bram. "Smoothed particle hydrodynamics for nonlinear solid mechanics". Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/11888.
Testo completoAbstract (sommario):
Includes abstract.Includes bibliographical references (leaves 115-117).
Smooth Particle Hydrodynamics (SPH) is one of the simplest meshless methods currently in use. The method has seen significant development and has been the germination point for many other meshless methods. The development of new meshless methods regularly uses standard SPH as a starting point, while trying to improve on issues related to consistency and stability. Despite these perceived flaws it is favoured by many researchers because of its simple structure and the ease with which it can be implemented.
7
Parameswaran, Gopalkrishnan. "Smoothed Particle Hydrodynamics studies of heap leaching hydrodynamics and thermal transport". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/39879.
Testo completoAbstract (sommario):
This thesis is concerned with the development and application of Smoothed Particle Hydrodynamics (SPH) models for studying multiphase flows such as those relevant to the analysis of the hydrodynamics and thermal transport involved in heap leaching. The improvements made here to the modelling aspects of multiphase SPH are seen to bring about measurable improvements to solution quality. A relative density formulation and a 'compressibility-matching' method for handling interfaces eliminate what would otherwise be significant obstacles to obtaining stable and smooth pressure fields. The convergence properties of the formulation are seen to approach the theoretically expected value in SPH. Convergence is also seen to strongly depend on the smoothing length factor used. A factor found to influence error magnitudes that nevertheless does not affect convergence rates is the extent of initial particle disorder. The simplified cases representative of heap leaching hydrodynamics studied through 2D simulations allow an understanding of flow at the particle scale. The significant dependence of mean flow rates in these systems on particle sizes, saturation and contact angle is shown. In 3D, saturated flows through packed beds of spherical particles are presented. Steady-state superficial velocities obtained through simulations, compared with analytical relationships given by Cozeny-Karman and Ergun relations are illustrative of the ability of SPH to reproduce packed bed flows satisfactorily. Subsequently unsaturated regimes encountered at the channel scale are studied qualitatively for saturation values typical of real heaps. A heat transfer model based on a formulation for single-phase SPH developed by Szewc et al. is implemented. The model's performance (in terms of Rayleigh numbers indicative of transition to unsteady convection in differentially heated cavities (DHCs)) is satisfactory when compared with the established single-phase results of Le Quere. Its application to an idealised unsaturated scenario demonstrates its useability for multiphase studies. Finally, an extension is made to the model to account for turbulent regime heat transport. This extension, deriving from one used for finite elements by Chatelain et al. is novel in the SPH context and lets the loss of stratification seen in DHCs at high Rayleigh numbers be predicted with reasonable accuracy.
8
Strand, Russell K. "Smoothed particle hydrodynamics modelling for failure in metals". Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/6773.
Testo completoAbstract (sommario):
It is generally regarded to be a difficult task to model multiple fractures leading to
fragmentation in metals subjected to high strain rates using numerical methods.
Meshless methods such as Smoothed Particle Hydrodynamics (SPH) are well suited to
the application of fracture mechanics, since they are not prone to the problems
associated with mesh tangling.
This research demonstrates and validates a numerical inter-particle fracture model for
the initiation, growth and subsequent failure in metals at high strain rate, applicable
within a Total Lagrangian SPH scheme. Total Lagrangian SPH performs calculations in
the reference state of a material and therefore the neighbourhoods remain fixed
throughout the computation; this allows the inter-particle bonds to be stored and tracked
as material history parameters. Swegle (2000) showed that the SPH momentum
equation can be rearranged in terms of a particle-particle interaction area. By reducing
this area to zero via an inter-particle damage parameter, the principles of continuum
damage mechanics can be observed without the need for an effective stress term, held at
the individual particles.
This research makes use of the Cochran-Banner damage growth model which has been
updated for 3D damage and makes the appropriate modifications for inter-particle
damage growth. The fracture model was tested on simulations of a 1D flyer plate impact
test and the results were compared to experimental data. The test showed that the model
can recreate the phenomena associated with uniaxial spall to a high degree of accuracy.
Some limited modelling was also conducted in 2 and 3 dimensions and promising
results were observed.
Research was also performed into the mesh sensitivity of the explosively driven Mock-
Holt experiment. 3D simulations using the Eulerian SPH formulation were conducted
and the best results were observed with a radial packing arrangement.
An in-depth assessment of the Monaghan repulsive force correction was also conducted
in attempt to eliminate the presence of the SPH tensile instability and stabilise the
available Eulerian SPH code. Successful results were observed in 1D, although the
results could not be replicated consistently in 2D. A further study was also conducted
into an approach that makes use of a partition of unity weighting to two different SPH
approximations of the same flow-field; one local and one non-local (or extended).
Unfortunately this approach could not be made to stabilise the code.
9
Spreng, Fabian [Verfasser]. "Smoothed Particle Hydrodynamics for Ductile Solids / Fabian Spreng". Aachen : Shaker, 2017. http://d-nb.info/1139583565/34.
Testo completo
10
Anathpindika, Sumedh V. "Smoothed particle hydrodynamics simulations of colliding molecular clouds". Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54779/.
Testo completoAbstract (sommario):
The galactic disk is largely composed of hot, rarefied gas also called the inter cloud medium (ICM). The cooler regions of the ICM are dominated by molecular species and dust. Immersed in this neutral medium are dense agglomerations of primarily H2, called giant molecular clouds (GMCs). The GMCs have a velocity dispersion of order a few km s_1, superimposed on their orbital motion. A GMC, over a single period of rotation of the galaxy, may undergo a few tens of collisions. In the present work, we investigate this rather violent phenomenon and examine the prospects of star formation in the post collision composite gas body. The star formation code, DRAGON, employed for the present work is ill equipped to study the effects of cloud collision on the chemical composition of the ICM. We draw a distinction between the regime of high velocity (precollision Mach numbers in excess of ten) and low velocity (precollision Mach numbers of order unity) cloud collisions, on the basis of the evolution of the gas slab produced in either cases. While the former leads to the formation of a dense shock compressed gas slab, the latter results in a dense pressure compressed gas slab. We observe that strong internal shear in a shock compressed slab suppresses gravitational instability in it. In particular, we observe evidence for the non-linear thin shell instability (NTSI) in the shocked slab formed in a head-on cloud collision. The slab thus dissipates thermal energy and upon the loss of thermal support, collapses to form a thin, long filament along the collision axis. Star formation proceeds in this filament. There is however, no evidence of the NTSI in the oblique shocked slab resulting from off centre cloud collisions, although it is dominated by internal shearing motion. On the other hand, the pressure compressed slab is dominated by gravitational instability and fragments, when the fastest growing mode dominates. The slab develops a number of floccules, which merge to form larger clumps and filamentary structures. The densest regions in these large scale structures then collapse gravitationally. We suggest this as a possible mechanism for the formation of star clusters. YSOs forming in filamentary structures are fed with material streaming along the axis of respective filaments. This material also transfers angular momentum to the accreting protostellar core and the attendant accretion disk is orthogonal to the angular momentum vector of this inflowing material. In the filaments resulting from the collapse of the post-collision shocked slab in a head-on cloud collision, we observe that the accretion disks circumscribing the sinks, are orthogonal to the filament. However, the gas slab resulting from a low velocity, off centre cloud collision is wrapped around by angular momentum and gravitationally fragments to form filaments. This slab tumbles in the plane of the collision (and therefore the axis about which it tumbles, comes out of this plane), the filaments in the slab also tumble with it. In the process they become offset relative to each other and feed angular momentum to the candidate protostellar core along the direction normal to the angular momentum axis. Thus, any attendant accretion disk is expected to be parallel to the filament (also the angular momentum) axis (Whitworth et al., 1995). To test this hypothesis, we collated data for YSOs located in filamentary star forming regions, and outflows originating from them. The scope of our work was limited and restricted to only five filamentary star forming regions in the local universe. Outflows from YSOs generally have small opening angles and are approximately normal to the circumstellar disk. Under this premise, we can get an idea of the orientation of the circumstellar disks relative to their natal filaments. We concluded that 72% outflows were distributed within 45 of being orthogonal to their natal filaments and 28% were distributed within 45 of being parallel to their natal filaments. It is difficult to make a strong claim simply on the basis of this work, which therefore needs to be extended. None the same, it tends to support the mechanism elucidated by Whitworth et al. (1995).
11
Connolly, Adam. "Smoothed particle hydrodynamics for high velocity impact simulations". Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/17983.
Testo completoAbstract (sommario):
The subject of this work is the application of the Smoothed Particle Hydrodynamics (SPH) method to modelling high-velocity impact dynamics. The first part of this thesis proposes an extension of the original first-order Godunov SPH scheme, for material with strength, to second-order in space using a time-splitting approach for the hydrodynamic and deviatoric components of the stress tensor. A non-linear slope-limiting procedure is used to extend the hydrodynamic component to second-order while the deviatoric component is discretized directly. Exact conservation of total energy is enforced in the new scheme using a time-centering approach for the velocity field. The new scheme is shown to perform well for a variety of one and two-dimensional fluid and solid-dynamics test cases. In particular, the numerical viscosity is shown to be lower than the original first-order scheme and particle clustering is less pronounced than in the standard artificial viscosity method. The second part of this thesis applies the newly developed SPH scheme to modelling high-velocity impacts on a synthetic porous poly-crystalline graphite material. In the course of investigation it was found that the applicability of the porous P - α equation of state is questionable for this type of graphite; an experimental investigation concluded that the assumptions required for the use of the porous equation of state are invalid. Therefore, an empirically derived polynomial equation of state is proposed instead. A widely used material model for brittle materials, based on the Continuum Damage Mechanics (CDM) approach, is used for the graphite deviatoric constitutive equation. In light of the time-splitting procedure, an algorithm for inclusion of CDM constitutive models was developed. Numerical simulations of high velocity impacts on the graphite material were then performed and compared with experimental results.
12
Ritchie, Benedict William. "Multiphase smoothed-particle hydrodynamics and the intracluster medium". Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367789.
Testo completo
13
Bao, Yanyao. "Smoothed Particle Hydrodynamics Simulations for Dynamic Capillary Interactions". Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/19592.
Testo completoAbstract (sommario):
Complex interactions in porous media play an important role on many industrial and geotechnical applications, such as groundwater treatment, porous catalysts, carbon geosequestration, and oil recovery. Rate-dependent wetting effects are of great significance in understanding the multiphase behaviours of porous media thus further throw light on engineering solutions to the above problems. In this thesis, a modified smoothed particle hydrodynamics (SPH) model is applied to simulate (1) the contact angle dynamics and (2) stretching of liquid bridge at meso-scale. This SPH model adopted an inter-particle force formulation with short-range repulsive force and long-range attractive force to take into account single-phase and multiphase interactions. Particularly, a newly-introduced viscous force is imposed at the liquid-solid interface to capture the rate-dependent behaviours of contact angle without prescribing additional arbitrary condition or force. After identification of model parameters, the rate-dependent contact angle behaviours are studied for both wetting and dewetting phenomena. By analysing the contact angle results of fluid at triple-line region with different moving speeds, the dynamic contact angles and corresponding capillary numbers can be correlated by power law functions. The derived correlation and constants are compared with different forms of empirical power law functions and the results are satisfactory. Moreover, we investigated the properties of stretching liquid bridges, including shape evolution, liquid transfer ratio and flow condition under dynamic loading. Different stretching rates are applied, and the shapes of liquid bridge at same breakup distance is presented. By differentiating the wettability of top and bottom substrates, the liquid transfer ratio regarding wettability difference and substrate moving speed is studied.
14
Ulrich, Christian [Verfasser], e Thomas [Akademischer Betreuer] Rung. "Smoothed-particle-hydrodynamics simulation of port hydrodynamic problems / Christian Ulrich. Betreuer: Thomas Rung". Hamburg-Harburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2013. http://d-nb.info/1048574903/34.
Testo completo
15
Ulrich, Christian Verfasser], e Thomas [Akademischer Betreuer] [Rung. "Smoothed-particle-hydrodynamics simulation of port hydrodynamic problems / Christian Ulrich. Betreuer: Thomas Rung". Hamburg-Harburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2013. http://nbn-resolving.de/urn:nbn:de:gbv:830-tubdok-12458.
Testo completo
16
Relaño, Castillo Antonio. "AxisSPH:devising and validating an axisymmetric smoothed particle hydrodynamics code". Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/83525.
Testo completoAbstract (sommario):
A two-dimensional axisymmetric implementation of the smoothed particle hydrodynamics (SPH) technique, called for short AxisSPH, has been described in this thesis, along with a number of basic tests and realistic applications. The main goal of this work was to fill a gap on a topic which has been scarcely addressed in the published literature concerning SPH.
Although the application of AxisSPH to the simulation of real problems is restricted to those systems which display the appropriate symmetry there are, however, many interesting examples of physical systems which evolve following the axisymmetric premise. These examples belong to a variety of scientific and technological areas such as, for example, astrophysics, laboratory astrophysics or inertial confinement fusion. Additionally AxisSPH can be also useful in convergence studies of the standard 3D-SPH technique because the higher resolution achieved in 2D can be used to benchmark the three-dimensional codes.
The main improvements implemented in AxisSPH with respect existing axisymmetric SPH formulations are summarized as follows:
1) We have derived simple analytical expressions for correction factors which largely improves the calculation of density and velocity in the vicinity of the z-axis. These expressions and their derivatives were given as a function of an adimensional parameter and do not increase the computational load of the scheme.
2) We have obtained the appropriate expression of the fluid Euler equations containing the new correction functions and their derivatives. Far enough from the singular axis, the scheme reduces to the standard formulation discussed by Brookshaw (2003).
3) A novel expression for the heat conduction term, which has to be added to the energy equation was devised and checked. This new term improves the description of the heat flux for those particles located at the axis neighborhoods.
4) Until now axisymmetric SPH hydrocodes handle artificial viscosity using a crude approach because it was treated as a simple restriction of the standard 3D Cartesian viscosity to 2D. Here we propose to calculate the viscous pressure as a combination of two terms, the first one is the (standard) Cartesian part and the second is the axis-converging part of the viscosity respectively. As expected this last term is of special relevance to simulate implosions.
5) We have developed an original method to incorporate gravity into AxisSPH. First the direct ring to ring force was found as a function of the Euclidean distance between the 2D particles. In second place the gravitational force on a given particle was obtained by summing the contributions of all N particles. We have also developed a more efficient scheme to obtain the gravitational force calculating the potential of the ring, instead the force because it involves lesser algebraic operations.
The scheme has been checked using a large number of tests cases. These tests range from very specific oriented to check a particular algorithm or a piece of physics, to rather complex ones intended to analyze the behavior of the scheme in potential real applications (ICF, jets, astrophysics). At least in one case, the head on collision of a pair of white dwarfs, the result of the simulations carried out using AxisSPH brings new, unpublished, scientific material.En esta tesis se ha desarrollado un código, que hemos llamado AxisSPH, en dos dimensiones axisimétrico a partir de la técnica conocida como SPH (“smooothed particle hydrodynamics”). AxisSPH ha sido validado después de realizar una serie de tests básicos y algunas simulaciones de situaciones reales. El objetivo principal de este trabajo ha sido llenar, en parte, el vacío existente al respecto en la literatura sobre SPH. Aunque sólo se puede aplicar AxisSPH en problemas reales que presenten la apropiada simetría, existen muchos ejemplos interesantes de sistemas físicos que presentan la simetría axial demandada. Existen ejemplos en campos de aplicación tanto científica como tecnológica, por ejemplo en astrofísica, en el llamado laboratorio de astrofísica o en fusión por confinamiento inercial (ICF). Otra interesante aplicación de AxisSPH puede ser su utilización en estudios de convergencia con otros códigos 3D-SPH debido a su mayor resolución, al tratarse de un código 2D. Las mejoras implementadas en el código AxisSPH en comparación con otros códigos axisimétricos SPH existentes se pueden resumir en los siguientes puntos: 1) Hemos deducido expresiones analíticas simples para unos factores de corrección que mejoran el cálculo de la densidad y la velocidad en las proximidades del eje z. Dichas expresiones y sus derivadas dependen de un parámetro adimensional que no incrementa mucho el peso computacional del esquema propuesto. 2) Hemos obtenido las expresiones adecuadas de las ecuaciones de Euler que contienen estas nuevas funciones correctoras y sus derivadas. Lejos del eje de singularidad estas ecuaciones se transforman en las de la formulación estándar propuesta por Brookshaw (2003). 3) Una expresión novedosa del término de conducción, que debe de añadirse a la ecuación de la energía, se ha propuesto y validado. Este nuevo término mejora la evolución del flujo de calor de las partículas situadas en las proximidades del eje z. 4) Hasta el momento los códigos hidrodinámicos SPH axisimétricos existentes trabajaban con una aproximación poco elaborada de la viscosidad artificial ya que consistían en una restricción a dos dimensiones de la viscosidad estándar 3D. En este trabajo proponemos el cálculo de la presión debida a la viscosidad como combinación de dos términos, el primero reflejo de la parte cartesiana y la segunda da cuenta de la parte relacionada con la convergencia en el eje. Como era de esperar este último término es de relevante importancia en la simulación de implosiones. 5) Hemos desarrollado un método original para incorporar el cálculo de la gravedad en el código AxisSPH. En primer lugar la fuerza directa de anillo a anillo y en segundo lugar la fuerza de la gravedad que sufre una determinada partícula a partir de la contribución del resto de las N partículas existentes. También hemos desarrollado un esquema más eficiente para calcular la gravedad a partir del cálculo del potencial del anillo en lugar del cálculo directo de la fuerza ya que implica un menor número de operaciones algebraicas. El método ha sido verificado con un gran número de test numéricos. Desde los más específicos orientados a comprobar la validez de un algoritmo particular o la capacidad para simular un fenómeno físico en particular, hasta simulaciones bastante más complejas, con la intención de validar la capacidad de simular aplicaciones potencialmente más reales (ICF, jets, astrofísica). Así, en al menos un caso, en la colisión frontal de dos enanas blancas, los resultados de la simulación utilizando AxisSPH pueden aportar material científico publicable.
17
He, Lisha. "Improvement and application of smoothed particle hydrodynamics in elastodynamics". Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11314/.
Testo completoAbstract (sommario):
This thesis explores the mesh-free numerical method, Smooth Particle Hydrodynamics (SPH), presents improvements to the algorithm and studies its application in solid mechanics problems. The basic concept of the SPH method is introduced and the governing equations are discretised using the SPH method to simulate the elastic solid problems. Special treatments are discussed to improve the stability of the method, such as the treatment for boundary problems, artificial viscosity and tensile instability. In order to improve the stability and efficiency, (i) the classical SPH method has been combined with the Runge-Kutta Chebyshev scheme and (ii) a new time-space Adaptive Smooth Particle Hydrodynamics (ASPH) algorithm has been developed in this thesis. The SPH method employs a purely meshless Lagrangian numerical technique for spatial discretisation of the domain and it avoids many numerical difficulties related to re-meshing in mesh-based methods such as the finite element method. The explicit Runge-Kutta Chebyshev (RKC) scheme is developed to accurately capture the dynamics in elastic materials for the SPH method in the study. Numerical results are presented for several test examples applied by the RKC-SPH method compared with other different time stepping scheme. It is found that the proposed RKC scheme offers a robust and accurate approach for solving elastodynamics using SPH techniques. The new time-space ASPH algorithm which is combining the previous ASPH method and the RKC schemes can achieve not only the adaptivity of the particle distribution during the simulation, but also the adaptivity of the number of stage in one fixed time step. Numerical results are presented for a shock wave propagation problem using the time-space ASPH method compared with the analytical solution and the results of standard SPH. It is found that using the dynamic adaptive particle refinement procedure with adequate refinement criterion, instead of adopting a fine discretisation for the whole domain, can achieve a substantial reduction in memory and computational time, and similar accuracy is achieved.
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Walker, Richard Thomas. "Computational Steering of Smoothed Particle Hydrodynamics Simulations for Astrophysics". Thesis, University of Kent, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499677.
Testo completo
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Pan, Kai Ph D. Massachusetts Institute of Technology. "Simulating fluid-solid interaction using smoothed particle hydrodynamics method". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109642.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 97-102).
The fluid-solid interaction (FSI) is a challenging process for numerical models since it requires accounting for the interactions of deformable materials that are governed by different equations of state. It calls for the modeling of large deformation, geometrical discontinuity, material failure, including crack propagation, and the computation of flow induced loads on evolving fluid-solid interfaces. Using particle methods with no prescribed geometric linkages allows high deformations to be dealt with easily in cases where grid-based methods would introduce difficulties. Smoothed Particle Hydrodynamics (SPH) method is one of the oldest mesh-free methods, and it has gained popularity over the last decades to simulate initially fluids and more recently solids. This dissertation is focused on developing a general numerical modeling framework based on SPH to model the coupled problem, with application to wave impact on floating offshore structures, and the hydraulic fracturing of rocks induced by fluid pressure. An accurate estimate of forces exerted by waves on offshore structures is vital to assess potential risks to structural integrity. The dissertation first explores a weakly compressible SPH method to simulate the wave impact on rigid-body floating structures. Model predictions are validated against two sets of experimental data, namely the dam-break fluid impact on a fixed structure, and the wave induced motion of a floating cube. Following validation, this framework is applied to simulation of the mipact of large waves on an offshore structure. A new numerical technique is proposed for generating multi-modal and multi-directional sea waves with SPH. The waves are generated by moving the side boundaries of the fluid domain according to the sum of Fourier modes, each with its own direction, amplitude and wave frequency. By carefully selecting the amplitudes and the frequencies, the ensemble of wave modes can be chosen to satisfy a real sea wave spectrum. The method is used to simulate an extreme wave event, with generally good agreement between the simulated waves and the recorded real-life data. The second application is the modeling of hydro-fracture initiation and propagation in rocks. A new general SPH numerical coupling method is developed to model the interaction between fluids and solids, which includes non-linear deformation and dynamic fracture initiation and propagation. A Grady-Kipp damage model is employed to model the tensile failure of the solid and a Drucker-Prager plasticity model is used to predict material shear failures. These models are coupled together so that both shear and tensile failures can be simulated within the same scheme. Fluid and solid are treated as a single system for the entire domain, and are computed using the same stress representation within a uniform SPH framework. Two new stress coupling approaches are proposed to maintain the stress continuity at the fluid-solid interface, namely, a continuum approach and stress-boundary-condition approach. A corrected form of the density continuity equation is implemented to handle the density discontinuity of the two phases at the interface. The method is validated against analytic solutions for a hydrostatic problem and for a pressurized borehole in the presence of in-situ stresses. The simulation of hydro-fracture initiation and propagation in the presence of in-situ stresses is also presented. Good results demonstrate that SPH has the potential to accurately simulate the hydraulic-fracturing phenomenon in rocks.
by Kai Pan.
Ph. D.
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Santos, Ricardo Dias dos. "Uma formulação implícita para o método Smoothed Particle Hydrodynamics". Universidade do Estado do Rio de Janeiro, 2014. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=6751.
Testo completoAbstract (sommario):
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorEm uma grande gama de problemas físicos, governados por equações diferenciais, muitas vezes é de interesse obter-se soluções para o regime transiente e, portanto, deve-se empregar técnicas de integração temporal. Uma primeira possibilidade seria a de aplicar-se métodos explícitos, devido à sua simplicidade e eficiência computacional. Entretanto, esses métodos frequentemente são somente condicionalmente estáveis e estão sujeitos a severas restrições na escolha do passo no tempo. Para problemas advectivos, governados por equações hiperbólicas, esta restrição é conhecida como a condição de Courant-Friedrichs-Lewy (CFL). Quando temse a necessidade de obter soluções numéricas para grandes períodos de tempo, ou quando o custo computacional a cada passo é elevado, esta condição torna-se um empecilho. A fim de contornar esta restrição, métodos implícitos, que são geralmente incondicionalmente estáveis, são utilizados. Neste trabalho, foram aplicadas algumas formulações implícitas para a integração temporal no método Smoothed Particle Hydrodynamics (SPH) de modo a possibilitar o uso de maiores incrementos de tempo e uma forte estabilidade no processo de marcha temporal. Devido ao alto custo computacional exigido pela busca das partículas a cada passo no tempo, esta implementação só será viável se forem aplicados algoritmos eficientes para o tipo de estrutura matricial considerada, tais como os métodos do subespaço de Krylov. Portanto, fez-se um estudo para a escolha apropriada dos métodos que mais se adequavam a este problema, sendo os escolhidos os métodos Bi-Conjugate Gradient (BiCG), o Bi-Conjugate Gradient Stabilized (BiCGSTAB) e o Quasi-Minimal Residual (QMR). Alguns problemas testes foram utilizados a fim de validar as soluções numéricas obtidas com a versão implícita do método SPH.
In a wide range of physical problems governed by differential equations, it is often of interest to obtain solutions for the unsteady state and therefore it must be employed temporal integration techniques. One possibility could be the use of an explicit methods due to its simplicity and computational efficiency. However, these methods are often only conditionally stable and are subject to severe restrictions for the time step choice. For advective problems governed by hyperbolic equations, this restriction is known as the Courant-Friedrichs-Lewy (CFL) condition. When there is the need to obtain numerical solutions for long periods of time, or when the computational cost for each time step is high, this condition becomes a handicap. In order to overcome this restriction implicit methods can be used, which are generally unconditionally stable. In this study, some implicit formulations for time integration are used in the Smoothed Particle Hydrodynamics (SPH) method to enable the use of larger time increments and obtain a strong stability in the time evolution process. Due to the high computational cost required by the particles tracking at each time step, the implementation will be feasible only if efficient algorithms were applied for this type of matrix structure such as Krylov subspace methods. Therefore, we carried out a study for the appropriate choice of methods best suited to this problem, and the methods chosen were the Bi-Conjugate Gradient (BiCG), the Bi-Conjugate Gradient Stabilized (BiCGSTAB) and the Quasi-Minimal Residual(QMR). Some test problems were used to validate the numerical solutions obtained with the implicit version of the SPH method.
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Mason, Luke Stephen. "Modelling cold spray splat morphologies using Smoothed Particle Hydrodynamics". Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/3090.
Testo completoAbstract (sommario):
The small scale, short duration and hostile environment for instrumentation presented by cold spray coating makes experimental observations challenging, and therefore requires computational models capable of capturing the splat formation process. Current coating models are dominated by the Finite Element Method (FEM); whilst this has lead to significant improvements in understanding, the method is limited due to the reliance on a mesh coupled with the significant strains and strain rates involved. Eulerian methods have also been applied but retrieval of material histories and accurate interface tracking remains challenging. The Smoothed Particle Hydrodynamics (SPH) method is a meshless method that combines the advantages of FEM and Eulerian approaches. The current work extends the work of applying SPH to solid mechanics with heat conduction, improved tensile stability corrections and a novel zero impedance boundary. Solver performance is increased with the application of the multi-threading capabilities of the C++ 11 standard. The development of the SPH solver is described, validated and benchmarked against known analytical and experimental test cases. An in-depth investigation of parameters affecting splat morphologies is performed. Finally, a model of a coating formation process involoving multiple feedstock impact events is described and analysed in order to demonstrate the capabilities of the newly developed solver.
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Green, Mashy David. "Sloshing simulations with the smoothed particle hydrodynamics (SPH) method". Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/45367.
Testo completoAbstract (sommario):
The main aims of this work are to identify, verify, and validate a smoothed particle hydrodynamics (SPH) method for simulating long duration transient and steady- state fluid sloshing in complex geometries. The validation will be carried out by comparing the SPH simulations against experimental data provided by ESA/ESTEC for transient and steady-state sloshing in a rectangular tank with a low filling ratio and of transient sloshing in a pill-shaped tank that exhibits transition from swaying to swirling waves. The experimental tests proved to be extremely challenging due to the low fill ratio of the rectangular tank and the long duration of both experiments. The main challenge is to devise a SPH scheme that balances spatial and temporal accuracy with an efficient computer implementation to produce accurate simulations at a reasonable computing cost. The investigation highlighted three issues of critical importance: the treatment of solid boundaries in order to limit the introduction numerical errors into the system; the application of a correct numerical dissipation scheme to reduce existing numerical errors; and the need for a massively parallel implementation. Careful examination of the most suitable techniques led to the adoption a cor- rected δ-SPH scheme that provides numerical dissipation to reduce spurious pressure oscillations, and a fixed ghost particle boundary condition to accurately impose wall boundary conditions. The proposed SPH methods were coded in the open source parallel code DualSPHysics. The implementation showed significant improvements in energy conservation and solution accuracy when compared to state-of-the-art SPH methods, and accurately reproduced known analytical solutions to linear sloshing. The validation against the ESA/ESTEC experimental data showed excellent agreement between the SPH simulations and experiments, accurately reproducing the time history of wave heights and sloshing forces as well as capturing the full free-surface shapes. Only the careful selection of appropriate boundary conditions, artificial dissipation and a massively parallel GPU architecture allowed to accurately simulate these experiments.
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Bai, Jinshuai. "A data-driven smoothed particle hydrodynamics method for fluids". Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/211354/1/Jinshuai_Bai_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis proposed a novel Data-Driven Smoothed Particle Hydrodynamics (DDSPH) method that, instead of applying the empirical rheological models, utilizes discrete experimental datasets to close the Navier-Stokes equations for hydrodynamic modelling. Besides, the chained hashing algorithm is applied to improve the efficiency of the data retrieval and the robustness of the method with respect to the noisy data is achieved via adding a variable that qualifies the relevance of data points to the clusters. The proposed DDSPH method introduces a new avenue for hydrodynamic modelling and has great potential for modelling complex fluids with highly nonlinear rheological relationships.
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Gathmann-Hüttemann, Stefan. "Untersuchungen über objektorientierte Design-Patterns für massiv-parallele Teilchensimulationsverfahren anhand von smoothed particle hydrodynamics". [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964104091.
Testo completo
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Gartner, Nicolas. "Identification de paramètres hydrodynamiques par simulation avec Smoothed Particle Hydrodynamics". Electronic Thesis or Diss., Toulon, 2020. http://www.theses.fr/2020TOUL0004.
Testo completoAbstract (sommario):
Cette thèse porte sur les techniques de simulations des interactions dynamiques entre un véhicule sous-marin et l'eau qui l'entoure. L'objectif principal est de proposer une solution satisfaisante pour pouvoir, en amont du processus de conception, tester des algorithmes de contrôle et des formes de coques pour véhicules sous-marins. Il serait alors intéressant de pouvoir simuler en même temps la dynamique du solide et celle du fluide. L'idée développée dans cette thèse est d'utiliser la technique Smoothed Particles Hydrodynamics (SPH), qui est très récente et qui modélise le fluide comme un ensemble de particules sans maillage. Afin de valider les résultats de simulations une première étude a été réalisée avec un balancier hydrodynamique. Cette étude a permis la mise au point d'une méthode innovante d'estimation de paramètre hydrodynamique (forces de frottement et masse ajoutée) qui est plus robuste que les méthodes existantes lorsqu'il est nécessaire d'utiliser des dérivées numériques du signal mesuré. Ensuite, l'utilisation de deux types de solveur SPH : Weakly Compressible SPH et Incompressible SPH, est validée en suivant la démarche de validation proposée dans cette thèse. Sont étudiés, premièrement, le comportement du fluide seul, deuxièmement, un cas hydrostatique, et enfin un cas dynamique. L'utilisation de deux méthodes de modélisation de l'interaction fluide-solide : la méthode de réflexion de la pression et la méthode d'extrapolation est étudiée. La capacité d'atteindre une vitesse limite due aux forces de frottement est démontrée. Les résultats d'estimation des paramètres hydrodynamiques à partir des essais de simulation est finalement discutée. La masse ajoutée simulée du solide s'approche de la réalité, mais les forces de frottement semblent actuellement ne pas correspondre à la réalité. Des pistes d'améliorations pour pallier à ce problème sont proposéesThis thesis focuses on techniques that allows the simulation of dynamic interactions between an underwater vehicle and the surrounding water. The main objective is to propose a satisfactory solution to be able to test control algorithms and hull shapes for underwater vehicles upstream of the design process. In those cases, it would be interesting to be able to simulate solid and fluid dynamics at the same time. The idea developed in this thesis is to use the Smoothed Particles Hydrodynamics (SPH) technique, which is very recent, and which models the fluid as a set of particles without mesh. In order to validate the simulation results a first study has been performed with a hydrodynamic pendulum. This study allowed the development of an innovative method for estimating the hydrodynamic parameters (friction forces and added mass) which is more robust than previous existing methods when it is necessary to use numerical derivatives of the measured signal. Then, the use of two types of SPH solver: Weakly Compressible SPH and Incompressible SPH, is validated following the validation approach proposed in this thesis. Firstly, the behaviour of the fluid alone is studied, secondly, a hydrostatic case, and finally a dynamic case. The use of two methods for modelling the fluid-solid interaction: the pressure mirroring method and the extrapolation method is studied. The ability to reach a limit velocity due to friction forces is demonstrated. The results of the hydrodynamic parameters estimation from simulation tests are finally discussed. The simulated added mass of the solid approaches reality, but the friction forces currently seem not to correspond to reality. Possible improvements to overcome this problem are proposed
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Jonsson, Patrick. "Smoothed particle hydrodynamics in hydropower applications : modeling of hydraulic jumps". Licentiate thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16867.
Testo completoAbstract (sommario):
In present thesis, the Lagrangian particle based method Smoothed ParticleHydrodynamics (SPH) is used to model two-dimensional problems associated with hydropower applications such as dam break evolution and hydraulic jumps. In the SPHmethod, the fluid domain is represented by a set of non-connected particles which possess individual material properties such as mass, density, velocity, position and pressure. Besides representing the problem domain and acting as information carriers the particles also act as the computational frame for the field function approximations. As the particles move with the fluid the material properties changes over time due to interaction with neighbouring particles. The adaptive nature of the SPH-method together with the nonconnectivity between the particles results in a method that is able to handle very large deformations as is the case for highly disordered free-surface flows such as hydraulic jumps.The dam break case was used as a model validation test case where the response of different parameter settings was explored. The SPH spatial resolution and the choice of artificial viscosity (a term in the momentum equation) constants had a major impact on the results. Increasing the spatial resolution increased the number of flow features resolved and setting the constants equal to unity resulted in a highly viscous and unphysical solution.Following the parameter study, the work focused on SPH simulations of hydraulic jumps. A hydraulic jump is a rapid transition from supercritical flow to subcritical flow characterized by the development of large scale turbulence, surface waves, spray, energy dissipation and considerable air entrainment. Several features of the jump were explored using the SPH method and good agreement with theory and experiments was obtained for e.g. the conjugate depth and the mean free surface elevation in the roller section. However, the free surface fluctuation frequencies were over predicted and the model could not capture the decay of fluctuations in the horizontal direction.Godkänd; 2013; 20130425 (patjon); Tillkännagivande licentiatseminarium 2013-05-29 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Patrick Jonsson Ämne: Strömningslära/Fluid Mechanics Uppsats: Smoothed Particle Hydrodynamics in Hydropower Applications Modelling of Hydraulic Jumps Examinator: Professor Staffan Lundström, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Doktor, forskare Gustaf Gustafsson, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Torsdag den 20 juni 2013 kl 09.00 Plats: E231, Luleå tekniska universitet
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Bhojwani, Shekhar. "Smoothed particle hydrodynamics modeling of the friction stir welding process". To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2007. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
Testo completo
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Stinson, Gregory. "Supernova feedback in smoothed particle hydrodynamics simulations of galaxy formation /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/5428.
Testo completo
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Johansson, Ann. "Video Games Fluid Flow Simulations Towards Automation : Smoothed Particle Hydrodynamics". Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-219951.
Testo completoAbstract (sommario):
A complete understanding of the cooling process when hot rolling steel is essential to understanding how the quality of the steel is connected to the cooling. This is why it is of great interest to simulate this process. However traditional CFD methods are too expensive in terms of CPU time. Knowing that video games successfully simulate fluids in reasonable time, those methods could be useful for simulating the cooling process in steel manufacturing. This would mean a loss in accuracy that could be acceptable. In this thesis different methods used for fluid simulations have been studied. The Smoothed Particle Hydrodynamics (SPH) method has been chosen. The method has been implemented for simulating the cooling process in MATLAB, which is a matrix operation based programming tool. Convincing results have been achieved for a big scale, but problems still remain for an implementation on a small scale.
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Yue, Thomas Chun Long. "Numerical simulation of multiphase jet fragmentation using Smoothed Particle Hydrodynamics". Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/28329/.
Testo completoAbstract (sommario):
This thesis is devoted to the study of multiphase jet fragmentation using Smoothed Particle Hydrodynamics (SPH). The theoretical aspects of three hydrodynamic instabilities, namely the Kelvin-Helmholtz instability (KHI), Rayleigh-Taylor instability (RTI), and Rayleigh Plateau instability (RPI) are reviewed. The linear growth rate of the combined KHI and RTI are derived by means of linear perturbation in chapter 2. The linear growth rate of the multiphase RPI is presented in chapter 7. An overview of the Smoothed Particle Hydrodynamics is given in chapter 3. A pseudo-consistent SPH scheme is presented for the simulation of multiphase flow problems. Additionally, two interface stabilisation models are presented: quasi-buoyancy model and gas-repulsion model. When used in combination with the pseudo-consistent SPH scheme, these models are found to be superior than those presented in the weakly-compressible SPH literature and allows for the simulations for density ratio up to three-magnitudes. The development of an idealised KHI and a KHI subjected to constant gravitational acceleration (stratified shear instability) is examined in chapter 5. The extracted linear growth rate are compared with the theoretical growth rate presented both in the literature and in chapter 2 for the purpose of validation. The development of a single- and multi-mode RTI are studied by means of SPH in chapter 6. Chapter 7 presents the results for the three-dimensional RPI occurring between two fluids. Based on the knowledge acquired in chapter 5-7, the multiphase jet fragmentation driven by the previously mentioned hydrodynamic instabilities are presented in chapter 8. Finally, the major research findings and recommendations are summarised in chapter 9.
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Jian, Wei. "Smoothed particle hydrodynamics modelling of dam-break flows and wave structure interactions". Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648472.
Testo completo
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Kiara, Areti. "Analysis of the smoothed particle hydrodynamics method for free-surface flows". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57890.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 306-309).
Smoothed Particle Hydrodynamics (SPH) is a simple and attractive meshless Lagrangian particle method with applications in many fields such as astrophysics, hydrodynamics, magnetohydrodynamics, gas explosions, and granular flows that has demonstrated ability to simulate highly non-linear free-surface flows including wave overturning, jets, and the formation of spray and droplets. Despite the increasing popularity and promise of the method, SPH has a number of key issues that must be overcome before the method can realize its full potential in scientific and engineering applications: it is of low order, requires a high degree of tuning, and is inherently unstable. Additionally, there exists little analytic basis or fundamental understanding of the method to guide the many ad-hoc tuning and empirical fixes. The objective of this thesis is to perform an analytical and numerical investigation of the SPH method for free-surface flows. To this end, we perform a quantitative, unified analysis of the numerical method and the physics it captures, and we assess the method's consistency, stability, and convergence. It is shown that SPH introduces spurious solutions dominant in the dynamics of the solution making quantities such as velocity and pressure essentially unusable without filtering. It is also shown that the method is consistent inside the domain but imposes spurious, leading order, dynamic free-surface boundary conditions which alter the flow and further permit the introduction of spurious solutions. We further extend the analysis to address the effects of different empirical SPH treatments introduced in the literature, classifying these respectively as accuracy, consistency, or stability treatments, and characterizing their effectiveness. Based on the findings of the analysis, we eliminate the tuneable and empirical nature of the method by providing rational guidelines for the usage and effects of the relevant SPH treatments. Finally, we propose a modified SPH method that maintains the key features of SPH and significantly reduces spurious errors present in current SPH implementations. This thesis is among the first to provide a unified systematic analysis of the SPH method, shedding insight into the many proposed variations and fixes, and informs and guides new rational improvements to the method. This work lays the foundation for the development of SPH as a valuable engineering tool in the study of violent free-surface flows.
by Areti Kiara.
Ph.D.
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Shen, Liang. "Applications of smoothed particle hydrodynamics on 3D nonlinear free surface flows". Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=17825.
Testo completo
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Sun, Fanfan. "Investigations of smoothed particle hydrodynamics method for fluid-rigid body interactions". Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/355957/.
Testo completoAbstract (sommario):
The aim of this project is to investigate the capability of smoothed particle hydrodynamics (SPH) method for fluid-rigid body interactions. SPH is one of the most widely used meshless methods which use particles to represent the system. The fluid is assumed either slightly compressible so weakly compressible SPH (WCSPH) is applied or truly incompressible so incompressible SPH method (ISPH) is adopted. The performance of SPH method is affected by a number of modelling parameters including the choice of kernel functions, smoothing length, total number of particles and time step size. Investigations of the effect of these parameters were conducted using one dimensional cases and the results show that smoothing length and the total number of particles can influence the accuracy significantly but other parameters are less important. In order to generate the model efficiently and maintain accuracy an appropriate boundary treatment is important. Two boundary treatments are investigated for ISPH method. Although these two boundary treatments have been used in WCSPH, they have not been used in ISPH method in the literature. They are easier to use for complicated engineering situations related to fluid structure interaction problems compared with the traditionally used ghost particles. Two approaches for solving Poisson’s equation of ISPH method are studied including the implicit solution approach and explicit solution approach. A new method is developed for multi-phase flow by combining WCSPH method and truly ISPH method to study the effect from air pressure. Within this method the compressibility of air and incompressibility of water can be retained. Based on these studies, algorithms for fluid rigid-body interaction in 2 dimensional and 3 dimensional cases have been developed to simulate the general engineering problems related to fluid rigid body interactions.
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Machrouki, Hicham. "Incompressibilité et conditions aux limites dans la méthode Smoothed particle hydrodynamics". Poitiers, 2012. http://theses.univ-poitiers.fr/25282/2012-Machrouki-Hicham-These.pdf.
Testo completoAbstract (sommario):
Nous présentons une méthode numérique particulaire pour résoudre les équations de Navier-Stockes en formulation vitesse-pression pour la modélisation bidimensionnelle des écoulements incompressibles en présence d'obstacles. Cette méthode s'appuie sur la formulation Smoothed particles hydrodynamics pour le calcul du transport des moments. L'absence de maillage structuré permet de traiter des domaines d'écoulement avec des frontières complexes. Par ailleurs, le calcul du champ de pression est réalisé par la résolution d'une équation de poisson assurant l'incompressibilité de l'écoulement et les conditions aux limites sont renforcées par l'utilisation de la méthode des intégrales de frontières. Cette dernière méthode est connue pour être pénalisante en termes de temps CFU. Pour remédier à ce problème, les contributions des termes sources de l'équation de poisson pour la pression et de l'équation de Helmhotz généralisée pour la vitesse sont calculées en superposant une grille cartésienne au domaine de l'écoulement et en utilisant une méthode de différences finies. Les différentes étapes de construction de la méthode que nous proposons ont été validées par l'étude de plusieurs cas académiques parmi lesquels l'écoulement dans une cavité, la rupture de barrage ou encore l'écoulement derrière un cylindre. En plus de son utilisation classique pour la modélisation des écoulements, notre méthode a été utilisée pour reconstruire les champs de vitesse et de pression à partir d'un champ de vitesse mesurée expérimentalement par PIV et appliquée au cas de l'écoulement autour d'un profil NACA en mouvementA numerical particle method for solving the Bavier-Stokes equations in velocity-pressure formulation for two dimensional incompressible flows is presented. The basis of the method is the Smoothed particle hydrodynamics (SPH) formulation for the moment transport. On advantage of this meshless method is an easy treatment of computational domains with complex boundaries. The pressure is computed by solving a poisson equation that ensures the flow incompressibility and the boundary conditions are imposed by using a boundary integral method (BIM). This last method, is known to be strongly CPU time consuming. To overcome this difficulty, the source term of the poisson equation was solved by introducing a cartesian grid and by using finite differences. The same treatment has been applied to the generalize Helmholtz equation for the velocity field as well. The different steps were validated by studying several academic cases including a driven cavity low, a dam break and an impulsively started flow around a circular cylinder. Aditionaly to this standard use for flow numerical modelling, the method was also applied for rebuilding the pressure and velocity fields from velocity fields experimentally measured by a PIV method. The method was then applied to the flow around a moving NACA profile
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Mokos, Athanasios Dorotheos. "Multi-phase modelling of violent hydrodynamics using Smoothed Particle Hydrodynamics (SPH) on Graphics Processing Units (GPUs)". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/multiphase-modelling-of-violent-hydrodynamics-using-smoothed-particle-hydrodynamics-sph-on-graphics-processing-units-gpus(a82b8187-f81a-400b-8bd2-9a74c502a953).html.
Testo completoAbstract (sommario):
This thesis investigates violent air-water flows in two and three dimensions using a smoothed particle hydrodynamics (SPH) model accelerated using the parallel architecture of graphics processing units (GPUs). SPH is a meshless Lagrangian technique for CFD simulations, whose major advantage for multi-phase flows is that the highly nonlinear behaviour of the motion of the interface can be implicitly captured with a sharp interface. However, prior to this thesis performing multi-phase simulations of large scale air-water flows has been prohibitive due to the inherent high computational cost. The open source code DualSPHysics, a hybrid central processing unit (CPU) and GPU code, is heavily modified in order to be able to handle flows with multiple fluids by implementing a weakly compressible multi-phase model that is simple to implement on GPUs. The computational runtime shows a clear improvement over a conventional serial code for both two- and three dimensional cases enabling simulations with millions of particles. An investigation into different GPU algorithms focuses on optimising the multi-phase SPH implementation for the first time, leading to speedups of up to two orders of magnitude compared to a CPU-only simulation. Detailed comparison of different GPU algorithms reveals a further 12% improvement on the computational runtime. Enabling the modelling of cases with millions of fluid particles demonstrates some previously unreported problems regarding the simulation of the air phase. A new particle shifting algorithm has been proposed for multi-phase flows enabling the air, initially simulated as a highly compressible liquid, to expand rapidly as a gas and prevent the formation of unphysical voids. The new shifting algorithm is validated using dam break flows over a dry bed where good agreement is obtained with experimental data and reference solutions published in the literature. An improvement over a corresponding single-phase SPH simulation is also shown. Results for dam break flows over a wet bed are shown for different resolutions performing simulations that were unfeasible prior to the GPU multi-phase SPH code. Good agreement with the experimental results and a clear improvement over the single-phase model are obtained with the higher resolution showing closer agreement with the experimental results. Sloshing inside a rolling tank was also examined and was found to be heavily dependent on the viscosity model and the speed of sound of the phases. A sensitivity analysis was performed for a range of different values comparing the results to experimental data with the emphasis on the pressure impact on the wall. Finally, a 3-D gravity-driven flow where water is impacting an obstacle was studied comparing results with published experimental data. The height of the water at different points in the domain and the pressure on the side of the obstacle are compared to a state-of-the-art single-phase GPU SPH simulation. The results obtained were generally in good agreement with the experiment with closer results obtained for higher resolutions and showing an improvement on the single-phase model.
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Lok, Tak-Shun Lawrence. "Analysis of smoothed particle hydrodynamics method for 2D free-surface flow applications". Thesis, Swansea University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599578.
Testo completo
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Bate, Matthew Russell. "The role of accretion in binary star formation". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388852.
Testo completo
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Oxley, Stephen. "Modelling the capture theory for the origin of planetary systems". Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313850.
Testo completo
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Muir, Stuart. "A relativisitic, 3-dimensional smoothed particle hydrodynamics (SPH) algorithm and its applications". Monash University, School of Mathematical Sciences, 2003. http://arrow.monash.edu.au/hdl/1959.1/9513.
Testo completo
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Müller, Alexandra [Verfasser]. "Dynamic Refinement and Coarsening for the Smoothed Particle Hydrodynamics Method / Alexandra Müller". Aachen : Shaker, 2017. http://d-nb.info/1124366555/34.
Testo completo
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Forgan, Duncan Hugh. "Probing self-gravitating protostellar discs using smoothed particle hydrodynamics and radiative transfer". Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/4883.
Testo completoAbstract (sommario):
Stars are likely to form with non-zero initial angular momentum, and will consequently possess a substantial gaseous protostellar disc in the early phases of their evolution. At this early stage, the disc mass is expected to be comparable to the mass of the protostar. The disc’s self-gravity therefore plays an important role in the subsequent evolution of the system, regulating the accretion of matter onto the protostar, as well as being potentially capable of forming low mass stars and massive planets by disc fragmentation. The protostellar disc may later evolve into a protoplanetary disc, providing the feedstock for planet formation. Therefore, if the current stellar populations and exoplanetary systems are to be understood, an understanding of the evolution of protostellar discs is crucial, especially their earliest self-gravitating phases. I have used various methods of numerical simulation to probe the physics of self-gravitating protostellar discs and their constituents. When constructing a model for self-gravitating protostellar discs, including detailed thermodynamics and radiative transfer is essential. I have developed two distinct numerical techniques for incorporating radiative transfer into Smoothed Particle Hydrodynamics (SPH) simulations. The first allows the modelling of frequency-averaged radiative transfer during the SPH simulation, in effect approximating radiative SPH (RSPH) with only a marginal increase in runtime (around 6%). The second takes the output from SPH simulations, and creates synthetic, wavelength-dependent telescope images and spectra of SPH systems. This allows the direct construction of observables from SPH simulations, providing, for the first time, a direct connection between the output of SPH simulations and observations. I have used these numerical methods to analyse, in detail, the local angular momentum transport induced by self-gravity in protostellar discs, testing the robustness of the “pseudo-viscous” analytical approximation for local disc stresses. I confirm that semi-analytical disc modellers are justified in using the pseudo-viscous approximation in some cases, but I also outline the limits in which non-local transport effects causes the approximation to fail. Also, I have investigated the evolution of protostellar discs when perturbed by a secondary companion, in particular identifying whether such events will in general trigger a) a disc fragmentation event, or b) a stellar outburst event. For case a), I found no significant evidence that perturbation by a companion improves the possibility of disc fragmentation in compact discs - in case b), I found that stellar outburst events do indeed occur, but they are unlikely to be seen by observers due to their rare occurrence, as well as due to self-obscuration effects.
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Whitehouse, Stuart Charles. "Radiative transfer using smoothed particle hydrodynamics and its application to star formation". Thesis, University of Exeter, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421588.
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Chen, Zipeng. "A Smoothed Particle Hydrodynamics Approach for Modelling Meso-scale Fluid–Fracture Interaction". Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/28188.
Testo completoAbstract (sommario):
The fluid–fracture interaction at meso-scale is vital in numerous applications and challenging for numerical studies. During this process, the solid deforms or even damages due to the force transmitted from the surrounding fluid, whereas the deformation and failure of the solid in turn change the flow behaviour. Besides, the surface tension and wettability at meso-scale can have considerable effects on fluid behaviour. As a particle-based approach, the smoothed particle hydrodynamics (SPH) has shown its capability in modelling the flow at multiscale and potential in reproducing the fracture. Therefore, to model the fluid–fracture interaction at meso-scale, this thesis aims to develop a modified SPH method considering the surface tension of fluid and the fracture propagation of solids at meso-scale.
In this approach, an interparticle force that can provide repulsive force in a short-range and attractive force in a long-range is introduced to model the fluid–fluid and fluid–solid interactions. Compared to traditional methods modelling the surface tension and wettability, the proposed interparticle force can be employed in complex geometry without explicitly identifying the fluid–solid interface. The formation of a droplet with surface tension and the change of contact angles on fluid–solid interface demonstrate the capability in reproducing the mesoscopic effects. Moreover, this interparticle force can prevent the SPH particles from clustering when under great pressure. The compressibility of the pipe flow is consistent with the physical value of water without particle clustering. This interparticle force is then coupled with the no-slip boundary to expand its application range. The simulation results of the Couette flow and the Poiseuille flow are consistent with the analytical solution, showing the feasibility of using this approach in the pipe flow under a no-slip boundary.
For the solid part, the Drucker–Prager (DP) model and the Grady–Kipp (GK) damage model are combined and implemented to describe the shear failure and tensile failure, respectively. A shear analytical model a biaxial compressive model and a uniaxial compressive experiment are simulated. The results show that the implemented DP model reproduces the shear failure well. After calibrating the GK damage model through the available uniaxial tensile test, the DP model is combined with the GK damage model. A Brazilian disc test is then simulated. The numerical results reproduce the fracture patterns consistent with the experimental ones, showing the feasibility of using this mixed solid model to express the complex fracture of rock-like material.
Finally, by coupling the fluid model and the solid model, an SPH framework is formed to consider the surface tension and fracture of the solid. A process of hydraulic fracturing is simulated at the meso-scale with different in-situ stress conditions. Moreover, a pre-existing flaw is added in the solid domain to investigate the influence of natural fracture in hydraulic fracturing. The results suggest that tensile failure is the dominant failure type controlling the fracture pattern of hydraulic fracturing. Moreover, since the in-situ stress state and the pre-existing flaw have mutual effects, the hydraulic fracturing should be analysed comprehensively. All the results prove that this modified SPH method had considerable potential in modelling the fluid–fracture interaction with the consideration of the surface tension effects of fluid and the fracture propagation of solid.
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Zerbe, Haoyue [Verfasser]. "Modeling of Laser Welding with the Smoothed Particle Hydrodynamics Method / Haoyue Zerbe". Düren : Shaker, 2020. http://d-nb.info/1211930874/34.
Testo completo
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Veen, Daniel John. "A smoothed particle hydrodynamics study of ship bow slamming in ocean waves". Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/1694.
Testo completoAbstract (sommario):
Smoothed Particle Hydrodynamics (SPH) is a mesh-free Lagrangian computational method suited to modelling fluids with a freely deforming surface. This thesis describes the development, validation and application of a two-dimensional Smoothed Particle Hydrodynamics algorithm to the problem of ship bow slamming in regular ocean waves. Slam events often occur in rough seas and have the potential to cause significant structural and payload damage due to the loads and subsequent whipping experienced by the ship. SPH is well suited to modelling ship bow slamming because the interaction between the bow of the ship and the water surface is of a freely deforming transient nature.The developed SPH algorithm was subjected to an extensive validation using both analytical and experimental data as a basis for comparison. The influence of each numerical correction – necessary for SPH stability – was evaluated using two theoretical problems free from the influence of external forces: the evolution of initially circular and square patches of fluid. Solid boundaries treated by the ghost particle technique were introduced and evaluated by way of the hydrostatic tank and the two-dimensional dam break.Still water impacts of two-dimensional wedges and hull cross-sections were simulated using the SPH algorithm and the results were compared with the experimental data of Aarsnes (1996), Whelan (2004) and Breder (2005). The complexity of the slamming problem was then increased by imposing the relative vertical velocity profile (between the hull and the water surface) measured during the ocean wave basin experiments of Hermundstad and Moan (2005) on a hull cross-section. Reasonable agreement between the simulated and experimental slamming pressures confirmed that the two-dimensional SPH algorithm could be applied to a three-dimensional problem through the use of a relative vertical velocity profile.Finally, the commercial ship motion prediction software SEAWAY and the validated SPH algorithm were combined in a 2D + t method to simulate bow slamming of a slender hull. The relative motion between the bow and the free water surface was extracted from the ship motion data and then imposed on a cross-section of a given hull form. Satisfactory agreement with the peak pressures measured on a model V-form hull in regular waves (Ochi, 1958) demonstrated that the developed two-dimensional SPH code is capable of modelling three-dimensional ship bow slamming.
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Lin, Yixin. "A Local Surface Reconstruction Algorithm for Surface Tension Simulation in Smoothed Particle Hydrodynamics". University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613752656589083.
Testo completo
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Meglicki, Zdzislaw, e Zdzislaw Meglicki [gustav@perth ovpit indiana edu]. "Analysis and Applications of Smoothed Particle Magnetohydrodynamics". The Australian National University. Research School of Physical Sciences, 1995. http://thesis.anu.edu.au./public/adt-ANU20080901.114053.
Testo completoAbstract (sommario):
Smoothed Particle Hydrodynamics (SPH) is analysed as the weighted residual method. In particular the analysis focuses on the collocation aspect of the method. Using Monte Carlo experiments we demonstrate that SPH is highly sensitive to node disorder, especially in its symmetrised energy and momentum conserving form. This aspect of the method is related to low [Beta] MHD instabilities observed by other authors. A remedy in the form of the Weighted Differences Method is suggested, which addresses this problem to some extent, but at a cost of losing automatic conservation of energy and momentum.
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The Weighted Differences Method is used to simulate propagation of Alfven and magnetosonic wave fronts in [Beta] = 0 plasma, and the results are compared with data obtained with the NCSA Zeus3D code with the Method of Characteristics (MOC) module.
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SPH is then applied to two interesting astrophysical situations: accretion on to a white dwarf in a compact binary system, which results in a formation of an accretion disk, and gravitational collapse of a magnetised vortex. Both models are 3 dimensional.
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The accretion disk which forms in the binary star model is characterised by turbulent flow: the Karman vortex street is observed behind the stream-disk interaction region. The shock that forms at the point of stream-disk interaction is controlled by the means of particle merges, whereas Monaghan-Lattanzio artificial viscosity is used to simulate Smagorinsky closure.
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The evolution of the collapsing magnetised vortex ends up in the formation of an expanding ring in the symmetry plane of the system. We observe the presence of spiralling inward motion towards the centre of attraction. That final state compares favourably with the observed qualitative and quantitative characteristics of the circumnuclear disk in the Galactic Centre. That simulation has also been verified with the NCSA Zeus3D run.
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In conclusions we contrast the result of our Monte Carlo experiments with the results delivered by our production runs. We also compare SPH and Weighted Differences against the new generation of conservative finite differences methods, such as the Godunov method and the Piecewise Parabolic Method. We conclude that although SPH cannot match the accuracy and performance of those methods, it appears to have some advantage in simulation of rotating flows, which are of special interest to astrophysics.
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Munro, David. "Toward a rigorous derivation of a stable and consistent smoothed particle hydrodynamics method". Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/11164.
Testo completoAbstract (sommario):
The aim of this thesis is to provide an investigation toward a rigorous derivation of a stable and consistent numerical method based on the established Smoothed Particle Hydrodynamics method. The method should be suitable for modelling the large deformation transient response of fluids and solids, the interests of the Crashworthiness, Impact and Structural Mechanics group (CISM) at Cranfield University.
A literature review of the current state of the art of the SPH method finds that the conventional SPH equations are not derived in a rigorous way, often the equations are manipulated into a mathematically equivalent form in order to preserve conservation of linear momentum, which often leads to different results; the reasons for this are unknown and it is not fully understood how each particular form of the discrete equations effects the solution in terms of stability, accuracy and convergence. This leads to specific objectives being defined which underpin the overall aim of the thesis.
The first objective is to develop an understanding of the SPH method and the implementation used at Cranfield University, this is done through a capability study which demonstrates the coupled SPH-FE method and a number of relevant improvements to the MCM code including the addition of a turbulence model and the modification of the SPH contact algorithm to model lateral forces between materials. This is demonstrated through the implementation of a friction model, which suggests that the contact algorithm is suitable for resolving lateral forces based on the relative velocity between materials, with the potential for coupling with a structural FE model ... [cont.].
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Hernández, Zubeldia Elizabeth. "Aplicação do método Smoothed Particle Hydrodynamics ao estudo de erosão superficial de solos". reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/23607.
Testo completoAbstract (sommario):
Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2017.Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2017-05-26T20:13:07Z No. of bitstreams: 1 2017_ElizabethHernándezZubeldia.pdf: 5346165 bytes, checksum: 7f1c1db1efc4694f63f446e4a9deef56 (MD5)
Approved for entry into archive by Raquel Viana (raquelviana@bce.unb.br) on 2017-05-30T11:39:16Z (GMT) No. of bitstreams: 1 2017_ElizabethHernándezZubeldia.pdf: 5346165 bytes, checksum: 7f1c1db1efc4694f63f446e4a9deef56 (MD5)
Made available in DSpace on 2017-05-30T11:39:16Z (GMT). No. of bitstreams: 1 2017_ElizabethHernándezZubeldia.pdf: 5346165 bytes, checksum: 7f1c1db1efc4694f63f446e4a9deef56 (MD5) Previous issue date: 2017-05-30
Neste trabalho é apresentada uma abordagem multifásica, que combina modelos constitutivos de fluidos com conceitos da hidráulica de canais abertos e critérios de ruptura próprios da Geomecânica, para simular problemas de erosão superficial usando o método numérico Smoothed Particle Hydrodynamics - SPH. Pela natureza Lagrangeana e sem malha, o método SPH fornece uma ferramenta numérica ideal para tratar problemas multifásicos, que envolvem superfícies livres e grandes deslocamentos de material, permitindo realizar simulações sob diversas condições de fluxo, em tempos relativamente curtos. Na abordagem proposta neste trabalho, a água e o sedimento são tratados como fluidos newtoniano e pseudonewtoniano, respectivamente, utilizando uma partícula em cada ponto do espaço físico. Um critério hidráulico, fundamentado no parâmetro de Shields, é utilizado para determinar o início do movimento das partículas, pela ação da água, em um leito de sedimentos. O critério consegue estimar adequadamente a massa de material erodido sob condições de fluxo de baixa velocidade, mas não permite simular a dinâmica do sedimento nas regiões subsuperficiais. O critério hidráulico foi combinado com um critério mecânico, baseado no critério de ruptura de Drucker-Prager, para determinar a viscosidade aparente do sedimento, cuja dinâmica é simulada por meio de um modelo visco plástico tipo Bingham, denominado Herschel-Bulkley-Papanastasiou (BHP). O modelo permite simular comportamentos pseudoplásticos e dilatantes do material. Os resultados de simulações de ensaios de ruptura de coluna da água (dam break) mostram a capacidade do modelo proposto ao reproduzir de forma satisfatória a quantidade de material removido da superfície do leito. Além disso, é possível estimar as interfaces entre os diversos materiais existentes no processo.
This theses presents a multiphase approach to simulate surface erosion using Smoothed Particles Hydrodynamics - SPH. The model combines constitutive models of fluids, concepts of open channel hydraulics and failure criteria of Geomechanics. Because of its Lagrangean formulation, SPH is an ideal numerical tool for the simulation of multiphase problems envolving with free surfaces and large deformation. The numerical simulation allows simulating different flux conditions in relatively short times. The model herein presented simulates the water and the sediment as Newtonian and pseudo Newtonian fluids, respectively, using a single particle to represent the points at the physical space. A hydraulic criterion based on the Shields’ parameter is used to determine the onset of sediment motion at the bed surface. The criterion estimates correctly the mass of eroded material under low velocity flux, but it doesn’t allow tracking the dynamic of the sediment at the subsurface region. The hydraulic criterion was combined with a mechanical criterion based on DruckerPrager failure criterion to determine the apparent viscosity of the sediment. The dynamic of the sediment is modelled by the viscoplastic Bingham type Herschel-Bulkley-Papanastasiou (BHP) model. The model is capable to reproduce shear thinning and shear thickening materials. Dam break simulations showed the capability of the model to simulate the amount of material removed from the sediment bed at the end of the experiment. Also, the ideal interfaces developed during the erosion process were satisfactorily estimated.