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Dissertations / Theses on the topic 'Boundary structure'

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Published: 4 June 2021
Last updated: 31 January 2023

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1

Schafer, Robert. "Tropical island boundary layer structure and development /." [Sydney : University of Technology, Sydney], 1998. http://grison.colorado.edu/Robert/paper/phd.pdf.

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2

Horsefield, Susan Jane. "Crustal structure across the continent-ocean boundary." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239628.

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3

Steeley, Glen D. "Boundary layer structure of an explosive cyclone." Thesis, Monterey, California. Naval Postgraduate School, 1990. http://hdl.handle.net/10945/30722.

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A detailed analysis of the horizontal boundary layer structure of the warm front of an open ocean explosive cyclone in Intensive Observation Period (IOP) 2 of the Experiment on Rapidly Intensifying Cyclones in the Atlantic (ERICA) is conducted. Data for this study consists of aircraft data averaged over one minute supplimented by satellite and drifting buoy observations. Analysis of surface winds and fluxes was done using the Brown-Liu Marine PBL model. Results show a PBL which differs from that found in typical cyclones, with large latent heat fluxes south of the warm front and with relatively weak sensible heat fluxes about the warm front. Boundary layer stratification was stable north of the warm front and unstable south of the warm front. A mechanism for moist frontogenesis is proposed whereby the destabilizing effects of the latent heat flux enhances frictional convergence along the warm front. These fluxes warm and moisten the cyclone's warm sector, enhancing unstable convection along the warm front and thereby enhancing the vertical motion. This enhanced vertical motion would strengthen the geostrophic deformation of the theta sub epsilon gradient and potentially enhance cyclogenesis.
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4

Vazquez, Isaura 1960. "On aluminum grain boundary structure and segregation." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/291693.

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The effect of an alloying agent, such as Mg, on Al grain boundary microstructure and chemistry was investigated. HREM measurements on an Al-5% Mg Σ = 5 (310) grain boundary showed Al grain boundary structure modification because of the presence of Mg. Chemical analysis, through TEM/STEM EDS of Al-2% Mg alloy, indicated the possibility of Mg segregation at Al grain boundaries, although this should be further investigated. An experiment is proposed to determine the change in grain boundary torque with impurity chemical potential. Molecular dynamic simulations of the effect of segregated vacancies was also studied. This study showed that grain boundaries act as sinks for vacancies. In addition, the presence of vacancies caused a relocation of the grain boundary plane, through a sliding-migration, or atomic restructuring of the boundary depending upon the vacancy distribution.
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5

Schulze, Bert-Wolfgang, and Jörg Seiler. "The edge algebra structure of boundary value problems." Universität Potsdam, 2001. http://opus.kobv.de/ubp/volltexte/2008/2595/.

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Boundary value problems for pseudodifferential operators (with or without the transmission property) are characterised as a substructure of the edge pseudodifferential calculus with constant discrete asymptotics. The boundary in this case is the edge and the inner normal the model cone of local wedges. Elliptic boundary value problems for non-integer powers of the Laplace symbol belong to the examples as well as problems for the identity in the interior with a prescribed number of trace and potential conditions. Transmission operators are characterised as smoothing Mellin and Green operators with meromorphic symbols.
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6

Peirce, Christine. "Crustal structure of the Africa-Eurasia plate boundary." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335167.

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7

Carmody, Matthew James. "The structure and logic of boundary-vague categories." Thesis, King's College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407188.

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8

Skelton, E. A. "Some mixed boundary problems of fluid-structure interaction." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47663.

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9

Adang, Thomas Charles. "Structure and dynamics of the Arizona Monsoon Boundary." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184693.

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The Arizona Monsoon Boundary is defined as the boundary separating two distinctly different air masses over Mexico, the southwestern United States, and the adjacent Pacific during the summer. The structure and dynamics of this boundary are examined by cross-sectional analysis using three different data sources: (1) a time-height cross section, constructed using radiosonde observations, at the time the boundary initially passed through Tucson in 1984; (2) a composite cross section through the boundary, constructed from the Fleet Numerical Oceanography Center analysis; and (3) a cross section through the boundary using high-resolution fields of temperature, moisture, and geopotential height obtained from the VISSR Atmospheric Sounder (VAS). All three cross sections showed similar structure. In some respects, the Arizona monsoon boundary resembles a mid-latitude front with a distinct and relatively sharp air mass change across the boundary, forced almost entirely by confluence. A direct ageostrophic circulation is produced by this forcing, giving weak ascent on the warm, moist side of the boundary. The gradients and flow associated with the composite boundary are weaker, by a factor of four, than those associated with strong mid-latitude fronts. However, the VAS cross section suggests that, at times, the strength of the boundary approaches that of middle-latitude fronts. The wind shear suggested by the composite boundary ought to be unstable to baroclinic or barotropic processes. Disturbances developing along the boundary have been observed. One example of such a disturbance is examined using GOES imagery, lightning strike data, cloud track winds, and VAS data. Satellite images show the disturbance resembling a mid-latitude occluded cyclone, with an apparent low pressure center over northern Baja California and front-like cloud features extending eastward and southward from the low. Lightning strike data show convective activity occurring along the front-like features. Wind data indicate the presence of a cyclonic circulation south of San Diego along the Baja California coast. Cross sections using VAS data suggest that barotropic and baroclinic energy sources are present and suggest the front-like nature of the cloud feature extending southward from the low pressure center. Additionally, a second disturbance that eventually interacted with the monsoon boundary is briefly examined using satellite imagery.
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10

Kannegieter, Timothy Hans. "Boundary weaving : the social structure and processes of organizational boundaries." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/46613/1/Timothy_Kannegieter_Thesis.pdf.

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Boundaries are an important field of study because they mediate almost every aspect of organizational life. They are becoming increasingly more important as organizations change more frequently and yet, despite the endemic use of the boundary metaphor in common organizational parlance, they are poorly understood. Organizational boundaries are under-theorized and researchers in related fields often simply assume their existence, without defining them. The literature on organizational boundaries is fragmented with no unifying theoretical basis. As a result, when it is recognized that an organizational boundary is "dysfunctional". there is little recourse to models on which to base remediating action. This research sets out to develop just such a theoretical model and is guided by the general question: "What is the nature of organizational boundaries?" It is argued that organizational boundaries can be conceptualised through elements of both social structure and of social process. Elements of structure include objects, coupling, properties and identity. Social processes include objectification, identification, interaction and emergence. All of these elements are integrated by a core category, or basic social process, called boundary weaving. An organizational boundary is a complex system of objects and emergent properties that are woven together by people as they interact together, objectifying the world around them, identifying with these objects and creating couplings of varying strength and polarity as well as their own fragmented identity. Organizational boundaries are characterised by the multiplicity of interconnections, a particular domain of objects, varying levels of embodiment and patterns of interaction. The theory developed in this research emerged from an exploratory, qualitative research design employing grounded theory methodology. The field data was collected from the training headquarters of the New Zealand Army using semi-structured interviews and follow up observations. The unit of analysis is an organizational boundary. Only one research context was used because of the richness and multiplicity of organizational boundaries that were present. The model arose, grounded in the data collected, through a process of theoretical memoing and constant comparative analysis. Academic literature was used as a source of data to aid theory development and the saturation of some central categories. The final theory is classified as middle range, being substantive rather than formal, and is generalizable across medium to large organizations in low-context societies. The main limitation of the research arose from the breadth of the research with multiple lines of inquiry spanning several academic disciplines, with some relevant areas such as the role of identity and complexity being addressed at a necessarily high level. The organizational boundary theory developed by this research replaces the typology approaches, typical of previous theory on organizational boundaries and reconceptualises the nature of groups in organizations as well as the role of "boundary spanners". It also has implications for any theory that relies on the concept of boundaries, such as general systems theory. The main contribution of this research is the development of a holistic model of organizational boundaries including an explanation of the multiplicity of boundaries . no organization has a single definable boundary. A significant aspect of this contribution is the integration of aspects of complexity theory and identity theory to explain the emergence of higher-order properties of organizational boundaries and of organizational identity. The core category of "boundary weaving". is a powerful new metaphor that significantly reconceptualises the way organizational boundaries may be understood in organizations. It invokes secondary metaphors such as the weaving of an organization's "boundary fabric". and provides managers with other metaphorical perspectives, such as the management of boundary friction, boundary tension, boundary permeability and boundary stability. Opportunities for future research reside in formalising and testing the theory as well as developing analytical tools that would enable managers in organizations to apply the theory in practice.
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11

Krainer, Thomas, and Bert-Wolfgang Schulze. "The conormal symbolic structure of corner boundary value problems." Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2008/2666/.

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Ellipticity of operators on manifolds with conical singularities or parabolicity on space-time cylinders are known to be linked to parameter-dependent operators (conormal symbols) on a corresponding base manifold. We introduce the conormal symbolic structure for the case of corner manifolds, where the base itself is a manifold with edges and boundary. The specific nature of parameter-dependence requires a systematic approach in terms of meromorphic functions with values in edge-boundary value problems. We develop here a corresponding calculus, and we construct inverses of elliptic elements.
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12

Lin, Feng. "Application of boundary element method to soil-structure interaction." Thesis, London South Bank University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358360.

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13

Luu, Van Chi. "Boundary-integral formulations for three-dimensional fluid-structure interaction." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/42518.

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14

Zhang, Xuan. "Structure of turbulence in combined wave-current boundary layers." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10057048/.

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This thesis is based on an experimental programme conducted in two laboratory flumes with different scales, to examine the near bed boundary layer under combined surface waves and a turbulent current. Flow conditions have covered a range of wave frequencies and amplitudes, and current conditions. The results give an enhanced understanding of turbulence structures close to the bed in a combined wave-current flow, in terms of coherent vortices and eddy viscosities. A two-dimensional Particle Image Velocimetry system was used to measure the velocity field. Average properties of turbulence characteristics were determined. Hydrogen bubble techniques were employed to provide flow visualisation of the near-wall flow patterns. Results for the unidirectional current are consistent with many previous studies on the existence of coherent vortices. In particular, the measured flow velocity vectors and contours of magnitude demonstrate the presence of low-speed and high-speed streaks in the wall region and bursts in the outer flow. Further quantitative analysis also shows that the characteristic length scales agree well with previous research. For tests with combined wave-current flow, results demonstrate that streamwise vortices are also present. However, the spacing between adjacent low-speed streaks changes periodically within one wave cycle. In addition, measurements also reveal that the maximum Reynolds shear stress induced by ejections is increased when waves are superimposed on the turbulent current. The increase is observed to be more significant for waves with higher frequencies and amplitudes. In order to relate turbulent behaviour with time-averaged velocities in a combined wave-current boundary layer, an eddy viscosity distribution was computed based on experimental results from the flumes and a large oscillating water tunnel from previous tests. These results show a different distribution from those in existing models of wave-current interaction. These results are expected to improve the accuracy on prediction of the hydrodynamics and sediment transport in combined wave-current flows.
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15

Reynolds, Ryan T. "Measurements of the structure of urban-type boundary layers." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/47099/.

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In order to gain a better understanding of the fundamental structure associated with turbulent flows over very rough, urban-type surfaces, laboratory experiments were undertaken in a subsonic wind tunnel facility at the University of Southampton. It was anticipated that undertaking this work would provide better insight into fundamental differences in the flow structure compared to smooth-wall surfaces. After modification of an existing facility to accommodate a longer working section length, testing proceeded over a regular array of cube roughness elements with a 25% area density. Measurements were conducted with hot-wire anemometry, Laser Doppler anemometry, and particle image velocimetry. Development of the particle image velocimetry technique to obtain accurate turbulence statistics over and among the roughness elements was successfully undertaken providing significant new analysis opportunities and results. Initial testing characterised a large-scale spanwise variation discovered within the boundary layer developing over the cube surface. It was found that mean velocity variation in the span at a height of 50% of the boundary layer thickness could exceed ±5%. Further testing was conducted at locations far enough downstream to minimise the amplitude of the variation. Time-averaged mean velocity and turbulence statistics were collected revealing the averaged flow features. The peak Reynolds shear stress near the cube surface was found to be a strong function of the relative boundary layer thickness compared to the roughness size. Quadrant analysis showed the instantaneous sweep motions found near the rough surface intermittently producing large percentages of the local shear stress. Spatial correlation analysis of the instantaneous field data collected with particle image velocimetry revealed long, streamwise-stretched regions of streamwise mean velocity cross correlation. Correlation analysis also allowed calculation of the structure angle of the streamwise velocity cross correlation and the associated integral length scales of the turbulence structure. Two integral length scales were found in certain locations near the cube surface highlighting the complex nature of the flow and inherent difference compared to smooth wall flows. Comparisons were made with existing direct numerical simulation studies over identical geometries showing many general similarities but also indicating differences associated with the assumptions governing each approach. Together, the experiments and analysis establish a broad picture of the distinct flow structure found in urban-type flows.
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16

Sagalowicz, Laurent. "Dislocation/grain boundary interactions in the diamond cubic structure /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487780865408123.

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17

Marella, Saikrishna V. Udaykumar H. S. "A Parallelized sharp-interface fixed grid method for moving boundary problems." Thesis supplements, 2006. http://ir.uiowa.edu/etd/88.

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18

O'Connor, Joseph. "Fluid-structure interactions of wall-mounted flexible slender structures." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/fluidstructure-interactions-of-wallmounted-flexible-slender-structures(1dab2986-b78f-4ff9-9b2e-5d2181cfa009).html.

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The fluid-structure interactions of wall-mounted slender structures, such as cilia, filaments, flaps, and flags, play an important role in a broad range of physical processes: from the coherent waving motion of vegetation, to the passive flow control capability of hair-like surface coatings. While these systems are ubiquitous, their coupled nonlinear response exhibits a wide variety of behaviours that is yet to be fully understood, especially when multiple structures are considered. The purpose of this work is to investigate, via numerical simulation, the fluid-structure interactions of arrays of slender structures over a range of input conditions. A direct modelling approach, whereby the individual structures and their dynamics are fully resolved, is realised via a lattice Boltzmann-immersed boundary model, which is coupled to two different structural solvers: an Euler-Bernoulli beam model, and a finite element model. Results are presented for three selected test cases - which build in scale from a single flap in a periodic array, to a small finite array of flaps, and finally to a large finite array - and the key behaviour modes are characterised and quantified. Results show a broad range of behaviours, which depend on the flow conditions and structural properties. In particular, the emergence of coherent waving motions are shown to be closely related to the natural frequency of the array. Furthermore, this behaviour is associated with a lock-in between the natural frequency of the array and the predicted frequency of the fluid instabilities. The original contributions of this work are: the development and application of a numerical tool for direct modelling of large arrays of slender structures; the characterisation of the behaviour of slender structures over a range of input conditions; and the exposition of key behaviour modes of slender structures and their relation to input conditions.
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19

Linn, Anthony B. "A computational study of turbulent structure formation." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-042607-093941/.

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20

Priedeman, Jonathan Lake. "Quantifying Grain Boundary Atomic Structures Using the Smooth Overlap of Atomic Positions." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6770.

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In this work, the relationship between grain boundary crystallography and grain boundary atomic structure is examined, using [1 0 0] - symmetric tilt grain boundaries in nickel. The structural unit model is used as a benchmark to evaluate the atomic structure description capacities of an emerging structural descriptor, the local environment representation, which itself is a refinement of the also-emergent Smooth Overlap of Atomic Positions (SOAP) descriptor. We show that the local environment representation encodes both the information of the structural unit model and additional information, such as distortion in the structural units and the arrangement of the structural units at the interface. The use of the local environment representation permits the use of a visualization tool known as SPRING to represent structural similarities between grain boundaries. With the SPRING representation, we produce objective evidence of a relationship between crystallography and atomic structure, at least for [1 0 0] - symmetric tilt grain boundaries.
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21

Efros, Vladislav. "Structure of turbulent boundary layer over a 2-D roughness." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13214.

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The roughness is an important parameter in wall-bounded flows, as most surfaces are rough. The main effect of the roughness is to increase the drag as the near wall is affected by the roughness. In recent years a lot of efforts has been used to find out what effect has the roughness on the outer layer. In other words is there any differences in outer layer, boundary layer or channel flow, between rough and smooth-surface? Jimenez (2004) suggests that for δ/k > 40 there are no differences, in agreement with Townsend’s hypothesis, the roughness merely acts to increase the surface stresses, without changing the structure in the flow. This was challenged by Krogstad et. al (1999) who showed, for boundary layer over 2−D roughness, there is a difference in the outer layer due to the roughness. However for a channel flow Krogstad et. al (2004) has found no differences. The main impediment is how to obtain a reliable estimate for the friction velocity, uτ, which is the main scaling parameter of principal interest. In channel flow the uτ may be obtained directly from the stream-wise pressure gradient. A common technique for boundary layer over smooth surface is the Clauser chart. This method is subjected to large uncertainties for rough surface, because the number of unknowns is increased from one, Cf , for smooth surface to three, (Cf , _, the shift in origin and Δu/uτ shift in velocity), for rough surface. The need for an independent measurement of the wall shear stress has led to the present work. A floating-balance has been designed to obtain the shear stress on the rough surface. The balance was tested in channel flow, adverse pressure gradient flow and zero pressure gradient boundary layer and the velocity field was investigated using a two-component LDA system. The results showed that the shear stress, from balance, was underestimated by ∼ 4%. Turbulent boundary layer is a complicated nonlinear system; Clauser (1956) compared it with a black box. A better understanding of this system may be obtained by changing one of its inputs and to examine its output. An experimental investigation on the response of a turbulent boundary layer to sudden change in roughness, from smooth to rough, using floating balance to measure the shear stress is also a part of the present work. The structure of the turbulent boundary layer over 2 − D roughness was invesitigated using LDA and PIV system. All the moments up to third order were determined from the LDA measurements. From the PIV measurements twopoint correlations in x − y plane were obtained. The effect of large scales on the features of the flow-using POD was also investigated
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22

Petton, Guy J. "Computer simulation study of grain boundary structure in B2 NiAl." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040708/.

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23

Macey, P. C. "Acoustic and structure interaction problems using finite and boundary elements." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.481846.

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24

Venkataraman, Rangarajan. "A study of grain boundary structure in B doped Ni3Al." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/94486.

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A theoretical and experimental study of Grain boundary structure in B doped Ni₃Al was carried out. Geometrical modelling was done to obtain the grain boundary structure in Ll₂ compounds for different misorientations between two grains. The size of interstitial sites in these boundaries was calculated to understand the segregation of B to the boundaries. Ratios of the B-B equilibrium interatomic distance to the nearest neighbour distances in various (A₃B) Ll₂ compounds were calculated, in an attempt to predict the grain boundary fracture behaviour in these compounds. Selected area channeling patterns were obtained from a number of grains to solve for the orientation relationship between grains, in order to predict the structure of the boundaries between them. A distribution of grain boundary structure that is different from the distribution for an undoped Ni₃Al is obtained in this work and is compared with results from other investigators.
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25

Comrie, Andrew Charles. "Growth, Structure and Prediction of the Thermal Internal Boundary Layer." Master's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/6920.

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The Thermal internal Boundary Layer (TIBL) is a dynamic and turbulent mesoscale feature of the coastal atmosphere that forms over the land during conditions of onshore flow. The TIBL develops as an adjustment of the atmospheric boundary layer to the discontinuities of temperature and roughness that occur at the interface between the underlying marine and terrestrial surfaces. The resulting formation of a characteristically convex mixed layer below relatively stable air aloft has serious implications for the dispersion of pollutants in shoreline environments. Although a wide range of research relating to various features of the TIBL may be found in the literature, relatively few broadly-based studies have been performed. This study has employed both airborne and surface measurements to obtain a comprehensive spatial and temporal data set, in order to elucidate aspects of the characteristic structure and behaviour of the TIBL. TIBL growth was found to follow a diurnal pattern, the initially irregular boundary becoming more uniform during the day as a steady balance between various factors was achieved. The TIBL was associated with a layer of uniform wind speed anti direction flowing perpendicular to the coastline, within which warmer temperatures and changes in relative humidity and moisture content were observed. The temperature structure of the onshore flow strongly influenced the intensity of turbulence encountered in the TIBL and the degree of entrainment aloft. Patterns of turbulent properties displayed significant increases in the TIBL, which were relatively abrupt near the surface and more gradual towards the top of the TIBL. Measurements of sensible heat flux revealed strong undulations in TIBL structure due to transitory eddies and thermal upcurrents. Certain theoretically based predictive equations of TIBL height displayed the best overall performance out of eight selected models, and some promise was shown by an empirical formulation. TIBL development was generally complex and irregular within the first few kilometres of the shore, while further inland more regular TIBL formation enabled the relatively accurate observation and prediction of TIBL height.
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26

Cai, Shang-Gui. "Computational fluid-structure interaction with the moving immersed boundary method." Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2276/document.

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Dans cette thèse, une nouvelle méthode de frontières immergées a été développée pour la simulation d'interaction fluide-structure, appelée la méthode de frontières immergées mobiles (en langage anglo-saxon: MIBM). L'objectif principal de cette nouvelle méthode est de déplacer arbitrairement les solides à géométrie complexe dans un fluide visqueux incompressible, sans remailler le domaine fluide. Cette nouvelle méthode a l'avantage d'imposer la condition de non-glissement à l'interface d'une manière exacte via une force sans introduire des constantes artificielles modélisant la structure rigide. Cet avantage conduit également à la satisfaction de la condition CFL avec un pas de temps plus grand. Pour un calcul précis de la force induite par les frontières mobiles, un système linéaire a été introduit et résolu par la méthode de gradient conjugué. La méthode proposée peut être intégrée facilement dans des solveurs résolvant les équations de Navier-Stokes. Dans ce travail la MIBM a été mise en œuvre en couplage avec un solveur fluide utilisant une méthode de projection adaptée pour obtenir des solutions d'ordre deux en temps et en espace. Le champ de pression a été obtenu par l'équation de Poisson qui a été résolue à l'aide de la méthode du gradient conjugué préconditionné par la méthode multi-grille. La combinaison de ces deux méthodes a permis un gain de temps considérable par rapport aux méthodes classiques de la résolution des systèmes linéaires. De plus le code de calcul développé a été parallélisé sur l'unité graphique GPU équipée de la bibliothèque CUDA pour aboutir à des hautes performances de calcul. Enfin, comme application de nos travaux sur la MIBM, nous avons étudié le couplage "fort" d'interaction fluide-structure (IFS). Pour ce type de couplage, un schéma implicite partitionné a été adopté dans lequel les conditions à l'interface sont satisfaites via un schéma de type "point fixe". Pour réduire le temps de calcul inhérent à cette application, un nouveau schéma de couplage a été proposé pour éviter la résolution de l'équation de Poisson durant les itérations du "point fixe". Cette nouvelle façon de résoudre les problèmes IFS a montré des performances prometteuses pour des systèmes en IFS complexe
In this thesis a novel non-body conforming mesh formulation is developed, called the moving immersed boundary method (MIBM), for the numerical simulation of fluid-structure interaction (FSI). The primary goal is to enable solids of complex shape to move arbitrarily in an incompressible viscous fluid, without fitting the solid boundary motion with dynamic meshes. This novel method enforces the no-slip boundary condition exactly at the fluid-solid interface with a boundary force, without introducing any artificial constants to the rigid body formulation. As a result, large time step can be used in current method. To determine the boundary force more efficiently in case of moving boundaries, an additional moving force equation is derived and the resulting system is solved by the conjugate gradient method. The proposed method is highly portable and can be integrated into any fluid solver as a plug-in. In the present thesis, the MIBM is implemented in the fluid solver based on the projection method. In order to obtain results of high accuracy, the rotational incremental pressure correction projection method is adopted, which is free of numerical boundary layer and is second order accurate. To accelerate the calculation of the pressure Poisson equation, the multi-grid method is employed as a preconditioner together with the conjugate gradient method as a solver. The code is further parallelized on the graphics processing unit (GPU) with the CUDA library to enjoy high performance computing. At last, the proposed MIBM is applied to the study of two-way FSI problem. For stability and modularity reasons, a partitioned implicit scheme is selected for this strongly coupled problem. The interface matching of fluid and solid variables is realized through a fixed point iteration. To reduce the computational cost, a novel efficient coupling scheme is proposed by removing the time-consuming pressure Poisson equation from this fixed point interaction. The proposed method has shown a promising performance in modeling complex FSI system
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27

Mawson, Mark. "Interactive fluid-structure interaction with many-core accelerators." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/interactive-fluidstructure-interaction-with-manycore-accelerators(a4fc2068-bac7-4511-960d-41d2560a0ea1).html.

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The use of accelerator technology, particularly Graphics Processing Units (GPUs), for scientific computing has increased greatly over the last decade. While this technology allows larger and more complicated problems to be solved faster than before it also presents another opportunity: the real-time and interactive solution of problems. This work aims to investigate the progress that GPU technology has made towards allowing fluid-structure interaction (FSI) problems to be solved in real-time, and to facilitate user interaction with such a solver. A mesoscopic scale fluid flow solver is implemented on third generation nVidia ‘Kepler’ GPUs in two and three dimensions, and its performance studied and compared with existing literature. Following careful optimisation the solvers are found to be at least as efficient as existing work, reaching peak efficiencies of 93% compared with theoretical values. These solvers are then coupled with a novel immersed boundary method, allowing boundaries defined at arbitrary coordinates to interact with the structured fluid domain through a set of singular forces. The limiting factor of the performance of this method is found to be the integration of forces and velocities over the fluid and boundaries; the arbitrary location of boundary markers makes the memory accesses during these integrations largely random, leading to poor utilisation of the available memory bandwidth. In sample cases, the efficiency of the method is found to be as low as 2.7%, although in most scenarios this inefficiency is masked by the fact that the time taken to evolve the fluid flow dominates the overall execution time of the solver. Finally, techniques to visualise the fluid flow in-situ are implemented, and used to allow user interaction with the solvers. Initially this is achieved via keyboard and mouse to control the fluid properties and create boundaries within the fluid, and later by using an image based depth sensor to import real world geometry into the fluid. The work concludes that, for 2D problems, real-time interactive FSI solvers can be implemented on a single laptop-based GPU. In 3D the memory (both size and bandwidth) of the GPU limits the solver to relatively simple cases. Recommendations for future work to allow larger and more complicated test cases to be solved in real-time are then made to complete the work.
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Hansen, Merethe Sirevåg. "Boundary Conditions for 3D Fluid-Structure Interaction Simulations of Compliant Vessels." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22739.

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The goal of this study was to investigate different outlet boundary conditions for a straight compliant tube, by the means of fluid-structure interaction simulations. In addition to investigating boundary conditions it was desirable to see how different parameters, like time step, grid refinement and CFL-number would influence the results. Simulations were run with different time steps and grids. Changing these parameters had only minor influence on the results of the simulations, except for very small time steps, when the simulations would not converge. Four different boundary conditions were tested at the outlet: A reflection free boundary, an imposed reflection factor of 0.9, a two-element Windkessel model and a three-element Windkessel model. The reflection free model gave almost no reflections, while the simulation with a reflection factor of 0.9 gave the imposed amount of reflections at the outlet. For the reflection free case, comparing the results with simpler, analytical solutions gave poor accuracy, because the assumption of Poiseuille flow was invalid. Changing the velocity profile at the inlet from uniform to parabolic improved the accuracy. The two-element Windkessel model was not able to model a reflection free outlet. Reflections would occur even when the parameters were chosen to give a theoretically reflection free outlet. This was improved by using the three-element Windkessel model. When choosing parameters that would theoretically give zero reflections, the amount of reflections was very low.
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Marra, Joseph J. "Relationship of grain boundary structure and mechanical properties of Inconel 690." Thesis, Cambridge, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/10945/4304.

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Stress corrosion cracking (SCC), failure due to environmentally assisted crack nucleation and propagation, is an important metallurgical problem with impact on current and future designs of ship structural components and nuclear reactors. SCC mechanism is dependent on the microstructure, particularly the grain boundaries, for a given alloy composition. This thesis investigated the relationship between the structural nature and the nanoscale mechanical properties on and near the grain boundaries to identify their role in the resistance to stress corrosion cracking. Inconel 690, an austenitic Ni-alloy, was chosen as the material of interest for its relevance in current applications in the nuclear energy technology. Inherent hardness of the solution annealed Inconel 690 were found to be the same for both the grain boundary and bulk regions, and did not vary with grain boundary type, specifically the 3 and high angle boundaries. These results indicate comparable ease of dislocation mobility and absorption at the different grain boundaries of Inconel 690 when indented at room temperature.
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Pufahl, Alexander G. "Vertical structure of the oceanic planetary boundary layer : a modelling approach." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363992.

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31

White, Martin George. "The temperature and current structure on the sloping benthic boundary layer." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315088.

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32

Bird, James William. "Controlling turbulent boundary layers through the actuation of a compliant structure." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/55878.

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The control of turbulent boundary layers through spanwise wall forcing has been the subject of extensive numerical and experimental investigation in recent years. It has been shown that the benefits of drag reduction and potential power saving are enhanced when the forcing takes the form of a streamwise travelling wave of spanwise velocity. When this wave has a certain non-dimensional frequency and wavenumber, large turbulent skin-friction drag reductions of almost 50% and potential net power savings of 38% can be achieved. While there are numerous direct numerical simulations (DNS) showing these trends, an experimental validation was lacking for boundary layer flows. The work presented details the design and manufacture of an active surface, capable of discretising these complex waveforms to bring about turbulent flow-control in a wind tunnel experiment. Through the optimal design of a compliant structure, based on the Kagome lattice geometry, an adaptive framework was developed which is capable of discretising waveforms through controlled local deformation. By combining this compliant structure with a pre-tensioned membrane, an active surface is produced. The surface, 3 m in length, is then driven pneumatically, producing surface travelling waves of variable wavenumber and phase velocity. Photogrammetric and vibrometer measurements of the static and dynamic performance of actuated surface are presented. Constant temperature anemometer measurements of the boundary layer were taken with and without the active surface applying forcing. A linear interpolation of the viscous sub-layer was performed to assess changes in wall shear-stress. For certain forcing parameters, a drag reduction of 20% was measured.
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Tan, Ming-yi. "A viscous boundary element approach to fluid flow-structure interaction problems." Thesis, University of Southampton, 1994. https://eprints.soton.ac.uk/253307/.

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34

Irfanoglu, Bulent. "Boundary Element-finite Element Acoustic Analysis Of Coupled Domains." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605360/index.pdf.

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This thesis studies interactions between coupled acoustic domain(s) and enclosing rigid or elastic boundary. Boundary element-finite element (BE-FE) sound-structure interaction models are developed by coupling frequency domain BE acoustic and FE structural models using linear inviscid acoustic and elasticity theories. Flexibility in analyses is provided by discontinuous triangular and quadrilateral elements in the BE method (BEM), and a rectangular plate and a triangular shell element in the FE method (FEM). An analytical formulation is developed for an extended fundamental sound-structure interaction problem that involves locally reacting sound absorptive treatment on interior elastic boundary. This new formulation is built upon existing analytical solutions for a configuration known as the cavity-backed-plate problem. Results from developed analytical formulation are compared against those from independent BE-FE analyses. Analytical and BE-FE analysis results for a selection of cavity-plate(s) interaction cases are given. Single- and multi-domain BE analyses of cavity-Helmholtz resonator interaction are provided as an alternative to modal method of acoustoelasticity. A discrete-form of the existing BE acoustic particle velocity formulation is presented and demonstrated on a basic case study. Both the existing and the discretized BE acoustic particle velocity formulations could be utilized in acoustic studies. A selection of case studies involving fundamental configurations are studied both analytically and computationally (by BE or BE-FE methods). These studies could provide a basis for benchmark case development in the field of acoustics.
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Thiriat, Paul. "FLUID-STRUCTURE INTERACTION : EFFECTS OF SLOSHING IN LIQUID-CONTAINING STRUCTURES." Thesis, KTH, Bro- och stålbyggnad, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-125353.

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This report presents the work done within the framework of my master thesis in the program Infrastructure Engineering at KTH Royal Institute of Technology, Stockholm. This project has been proposed and sponsored by the French company Setec TPI, part of the Setec group, located in Paris. The overall goal of this study is to investigate fluid-structure interaction and particularly sloshing in liquid-containing structures subjected to seismic or other dynamic action. After a brief introduction, the report is composed of three main chapters. The first one presents and explains fluid-structure interaction equations. Fluid-structure interaction problems obey a general flow equation and several boundary conditions, given some basic assumptions. The purpose of the two following chapters is to solve the corresponding system of equations. The first approach proposes an analytical solution: the problem is solved for 2D rectangular tanks. Different models are considered and compared in order to analyze and describe sloshing phenomenon. Liquid can be decomposed in two parts: the lower part that moves in unison with the structure is modeled as an impulsive added mass; the upper part that sloshes is modeled as a convective added mass. Each of these two added mass creates hydrodynamic pressures and simple formulas are given in order to compute them. The second approach proposes a numerical solution: the goal is to be able to solve the problem for any kind of geometry. The differential problem is resolved using a singularity method and Gauss functions. It is stated as a boundary integral equation and solved by means of the Boundary Element Method. The linear system obtained is then implemented on Matlab. Scripts and results are presented. Matlab programs are run to solve fluid-structure interaction problems in the case of rectangular tanks: the results concur with the analytical solution which justifies the numerical solution. This report gives a good introduction to sloshing phenomenon and gathers several analytical solutions found in the literature. Besides, it provides a Matlab program able to model effects of sloshing in any liquid-containing structures.
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Cross, Patrick S. "The California coastal jet : synoptic controls and topographically induced mesoscale structure /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FCross.phd.pdf.

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37

Andrade, Prashant William. "Implementation of second-order absorbing boundary conditions in frequency-domain computations /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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38

MacAulay, Phillip N. "An investigation of structure in a turbulent boundary layer developing on a smooth wall." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30002.

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The structure of a stable smooth wall zero pressure gradient turbulent boundary layer is investigated experimentally in order to determine the dominant outer region structure and to develop a hypothetical generalized boundary layer flow model. Three hot wire configurations, two vertically separated X-wires and a leading straight wire, a horizontal rake of 5 straight wires, and a vertical rake of 5 straight wires were used in the experiments, conducted at Reɵ = 8200. The basis for data reduction procedures came from crosscorrelations and the Variable Interval Time Average (VITA) technique. Three structure types are reported in the literature to be important: streaks and counter rotating streamwise vorticity, wall scaled hairpins or ring vortices, and large scale (0(ઠ)) bulges. A simple pictorial model consisting of three Reɵ dependent interdeveloping stages, which integrate all three structure types, is presented and discussed in relation to the literature and experiments performed. The rake data indicate that the positive ([formula omitted]u/[formula omitted]t) VITA detected velocity front has a scale much larger than that of the wall scaled eddies which typically have a scale of 100-300 y[formula omitted], and that this velocity front exhibits characteristics that are consistent with the trailing velocity front described in the model. The general convection velocity from basic crosscorrelations and the convection velocity of the positive VITA detected velocity front both had values 90-100% of the local mean velocity over most of the boundary layer. Evidence of small scale structure concentration on the downstream edge of the trailing velocity front is presented. A new method used to determine the average structure inclination angle associated with the trailing velocity front is presented and demonstrates that the generalized structure inclination angle, calculated from basic crosscorrelations between vertically separated sensors, does not indicate structure shape, but is associated with the bulk flow associated with the structure. The new method appears to give results that are consistent with flow visualization and more accurately estimates the inclination angle associated with the most dominant feature of the outer flow, the positive VITA velocity front. Although the model presented is somewhat crude and further development and refinement are required, the model appears to agree with most data in the literature, as well as the present experimental results.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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39

Madani, Kermani Seyed Hossein. "Application of immersed boundary method to flexible riser problem." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/9605.

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In the recent decades the Fluid-Structure Interaction (FSI) problem has been of great interest to many researchers and a variety of methods have been proposed for its numerical simulation. As FSI simulation is a multi-discipline and a multi-physics problem, its full simulation consists of many details and sub-procedures. On the other hand, reliable FSI simulations are required in various applications ranging from hemo-dynamics and structural engineering to aero-elasticity. In hemo-dynamics an incompressible fluid is coupled with a flexible structure with similar density (e.g. blood in arteries). In aero-elasticity a compressible fluid interacts with a stiff structure (e.g. aircraft wing) or an incompressible flow is coupled with a very light structure (e.g. Parachute or sail), whereas in some other engineering applications an incompressible flow interacts with a flexible structure with large displacement (e.g. oil risers in offshore industries). Therefore, various FSI models are employed to simulate a variety of different applications. An initial vital step to conduct an accurate FSI simulation is to perform a study of the physics of the problem which would be the main criterion on which the full FSI simulation procedure will then be based. In this thesis, interaction of an incompressible fluid flow at low Reynolds number with a flexible circular cylinder in two dimensions has been studied in detail using some of the latest published methods in the literature. The elements of procedures have been chosen in a way to allow further development to simulate the interaction of an incompressible fluid flow with a flexible oil riser with large displacement in three dimensions in future. To achieve this goal, a partitioned approach has been adopted to enable the use of existing structural codes together with an Immersed Boundary (IB) method which would allow the modelling of large displacements. A direct forcing approach, interpolation / reconstruction, type of IB is used to enforce the moving boundary condition and to create sharp interfaces with the possibility of modelling in three dimensions. This provides an advantage over the IB continuous forcing approach which creates a diffused boundary. And also is considered as a preferred method over the cut cell approach which is very complex in three dimensions with moving boundaries. Different reconstruction methods from the literature have been compared with the newly proposed method. The fluid governing equation is solved only in the fluid domain using a Cartesian grid and an Eulerian approach while the structural analysis was performed using Lagrangian methods. This method avoids the creation of secondary fluid domains inside the solid boundary which occurs in some of the IB methods. In the IB methods forces from the Eulerian flow field are transferred onto the Lagrangian marker points on the solid boundary and the displacement and velocities of the moving boundary are interpolated in the flow domain to enforce no-slip boundary conditions. Various coupling methods from the literature were selected and improved to allow modelling the interface and to transfer the data between fluid and structure. In addition, as an alternative method to simulate FSI for a single object in the fluid flow as suggested in the literature, the moving frame of reference method has been applied for the first time in this thesis to simulate Fluid-Structure interaction using an IB reconstruction approach. The flow around a cylinder in two dimensions was selected as a benchmark to validate the simulation results as there are many experimental and analytical results presented in the literature for this specific case.
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40

Dasi, Lakshmi P. "The small-scale structure of passive scalar mixing in turbulent boundary layers." Diss., Available online, Georgia Institute of Technology, 2004, 2004. http://etd.gatech.edu/theses/available/etd-08132004-065041/.

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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.
Cvitanovic, Predrag, Committee Member ; Roberts, Phillip, Committee Member ; Sturm, Terry, Committee Member ; Webster, Donald, Committee Chair ; Yeung, Pui-Kuen, Committee Member.
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41

Guthrie, Vanessa M. "Dynamics of eastern boundary currents and their effects on sound speed structure." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FGuthrie.pdf.

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Thesis (M.S. in Physcial Oceanography)--Naval Postgraduate School, June 2006.
Thesis Advisor(s): Mary L. Batteen, John A. Colosi. "June 2006." Includes bibliographical references (p. 69-73). Also available in print.
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42

Söderberg, Stefan. "Mesoscale dynamics and boundary-layer structure in topographically forced low-level jets." Doctoral thesis, Stockholm University, Department of Meteorology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-63.

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Two types of mesoscale wind-speed jet and their effects on boundary-layer structure were studied. The first is a coastal jet off the northern California coast, and the second is a katabatic jet over Vatnajökull, Iceland. Coastal regions are highly populated, and studies of coastal meteorology are of general interest for environmental protection, fishing industry, and for air and sea transportation. Not so many people live in direct contact with glaciers but properties of katabatic flows are important for understanding glacier response to climatic changes. Hence, the two jets can potentially influence a vast number of people.

Flow response to terrain forcing, transient behavior in time and space, and adherence to simplified theoretical models were examined. The turbulence structure in these stably stratified boundary layers was also investigated. Numerical modeling is the main tool in this thesis; observations are used primarily to ensure a realistic model behavior.

Simple shallow-water theory provides a useful framework for analyzing high-velocity flows along mountainous coastlines, but for an unexpected reason. Waves are trapped in the inversion by the curvature of the wind-speed profile, rather than by an infinite stability in the inversion separating two neutral layers, as assumed in the theory. In the absence of blocking terrain, observations of steady-state supercritical flows are not likely, due to the diurnal variation of flow criticality.

In many simplified models, non-local processes are neglected. In the flows studied here, we showed that this is not always a valid approximation. Discrepancies between simulated katabatic flow and that predicted by an analytical model are hypothesized to be due to non-local effects, such as surface inhomogeneity and slope geometry, neglected in the theory. On a different scale, a reason for variations in the shape of local similarity scaling functions between studies is suggested to be differences in non-local contributions to the velocity variance budgets.

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Söderberg, Stefan. "Mesoscale dynamics and boundary-layer structure in topographically forced low-level jets /." Stockholm : Meteorologiska institutionen, Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-63.

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44

Conroy, David. "The structure and kinematic history of the Walls Boundary Fault in Shetland." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318880.

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45

Orchard, D. M. "The near-wall structure of the thermal turbulent boundary layer over riblets." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339557.

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46

Aoi, Shin. "Boundary Shape Waveform Inversion for Two-Dimensional Basin Structure using Array Data." 京都大学 (Kyoto University), 1996. http://hdl.handle.net/2433/86230.

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47

Nasiri, Farshad. "The Structure of Boundary Layer Along a Vertical, Surface-Piercing Flat Plate." Thesis, The George Washington University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10842581.

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The present work reports on Direct Numerical Simulations of a temporally developing, zero pressure gradient, turbulent boundary along a surface piercing flat plate and its interaction with the free surface. The simulations were driven by experiments of the same flow regime. Three separate Froude numbers were considered in increasing order. Consequently the interface progresses from a rigid and undisturbed surface to one with violent eruptions, breaking waves and air entrainment. At the lowest Froude number where the surface stays flat, the simulations agreed well with prior studies and captured the recirculation regions in the cross-stream plane which are shown to be due to Reynolds stress anisotropy. At intermediate Froude numbers it was found that the main source of vorticity beneath the surface is not the Reynolds stress anisotropy but rather the vorticity generated at the interface. This vorticity was found to affect turbulent statistics including distribution of friction velocity and the slope of the log-law layer. Moreover, the present work shows that the surface generated vorticity interacts mainly with eddies of small and intermediate wave numbers and the smaller scales with high wave numbers remain intact.

Air entrainment due to turbulence was also investigated. With the aid of a prototypical problem the parameters that play a role in entrainment are established. A novel approach to quantify the turbulent structures was defined. Using this method, turbulent structures were categorized into entraining and non-entraining vortices. A Linear Logistic Regression model was trained and validated to help predict future entrainment events. The model performs well and can accurately predict entrainment events for both the turbulent regime and the prototypical problem.

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48

Shen, Jian. "Boundary Layer Structure in Homogeneous Tidal Flows: A Theoretical and Numerical Study." W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539617653.

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Javakhishvili, Zurab. "The coupled finite-boundary element method applied to the analysis of geotechnical engineering problems." Thesis, London South Bank University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261020.

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Kulkova, S. E., A. V. Bakulin, S. S. Kulkov, S. Hocker, and S. Schmauder. "Influence of Interstitial Impurities (H, B, C) on Grain Boundary Cohesion in B2 Ti-based Alloys." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35519.

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The investigation of hydrogen, boron and carbon sorption properties at the Σ5(310) symmetrical tilt grain boundary (GB) and (310) free surface (FS) in B2 Ti-based alloys was carried out by the plane-wave pseudopotential method within density functional theory. The most preferential positions for interstitial impurities at GB were determined. It was shown that impurities sorption energies at GB depend strongly on their local environment. The analysis of electronic properties allows us to establish the microscopic na-ture of chemical bonding of all considered impurities at GB. It was shown that H decreases more signifi-cantly the surface energies than the GB energy in contrast to B and C. This results in decreasing the Grif-fith work that indicates also the decrease of the strength of grain boundary. The segregation of H at the GB makes intergranular fracture much easier because the bonding between metal atoms, which are neigh-bors of H, is weakened. The segregation behavior of hydrogen confirms it as an embrittler for B2 Ti-based alloys. At the same time boron and carbon segregation contrast to hydrogen increase the GB cohesion. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35519
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