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Vierendeels, J., K. Dumont i P. R. Verdonck. "A partitioned strongly coupled fluid-structure interaction method to model heart valve dynamics". Journal of Computational and Applied Mathematics 215, nr 2 (czerwiec 2008): 602–9. http://dx.doi.org/10.1016/j.cam.2006.04.067.
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Suliman, Ridhwaan, i Oliver Oxtoby. "A Quadratic Elasticity Formulation for Dynamic Interacting Structures in Flow". MATEC Web of Conferences 347 (2021): 00033. http://dx.doi.org/10.1051/matecconf/202134700033.
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The deformation of slender elastic structures due to the motion of surrounding fluid is a common multiphysics problem encountered in many applications. In this work we detail the development of a numerical model capable of solving such strongly-coupled fluid-structure interaction problems, and analyse the dynamic behaviour of multiple interacting bodies under fluid loading. In most fluid-structure interaction problems the deformation of slender elastic bodies is significant and cannot be described by a purely linear analysis. We present a new formulation to model these larger displacements. By extending the standard modal analysis technique for linear structural analysis, the governing equations and boundary conditions are updated to account for non-linear terms and a new modal formulation with quadratic modes is derived. The quadratic modal approach is tested on standard benchmark problems of increasing complexity and compared with analytical and full non-linear numerical solutions. An analysis of the dynamic interactions between multiple finite plates in various configurations under fluid loading, as well as the effects of the spacing between the structures, is also conducted. Numerical results are compared with theoretical and experimental approaches. The inverted hydrodynamic drafting effect of elastic bodies in an in-line configuration can be confirmed from our numerical simulations.
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Girfoglio, Michele, Annalisa Quaini i Gianluigi Rozza. "Fluid-structure interaction simulations with a LES filtering approach in solids4Foam". Communications in Applied and Industrial Mathematics 12, nr 1 (1.01.2021): 13–28. http://dx.doi.org/10.2478/caim-2021-0002.
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Abstract The goal of this paper is to test solids4Foam, the fluid-structure interaction (FSI) toolbox developed for foam-extend (a branch of OpenFOAM), and assess its flexibility in handling more complex flows. For this purpose, we consider the interaction of an incompressible fluid described by a Leray model with a hyperelastic structure modeled as a Saint Venant-Kirchho material. We focus on a strongly coupled, partitioned fluid-structure interaction (FSI) solver in a finite volume environment, combined with an arbitrary Lagrangian-Eulerian approach to deal with the motion of the fluid domain. For the implementation of the Leray model, which features a nonlinear differential low-pass filter, we adopt a three-step algorithm called Evolve-Filter-Relax. We validate our approach against numerical data available in the literature for the 3D cross flow past a cantilever beam at Reynolds number 100 and 400.
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MANGANO, G., G. MIELE i V. PETTORINO. "COUPLED QUINTESSENCE AND THE COINCIDENCE PROBLEM". Modern Physics Letters A 18, nr 12 (20.04.2003): 831–42. http://dx.doi.org/10.1142/s0217732303009940.
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We consider a model of interacting cosmological constant/quintessence, where dark matter and dark energy behave as, respectively, two coexisting phases of a fluid, a thermally excited Bose component and a condensate, respectively. In a simple phenomenological model for the dark components interaction we find that their energy density evolution is strongly coupled during the universe evolution. This feature provides a possible way out for the coincidence problem affecting many quintessence models.
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Joosten, M. M., W. G. Dettmer i D. Perić. "Analysis of the block Gauss-Seidel solution procedure for a strongly coupled model problem with reference to fluid-structure interaction". International Journal for Numerical Methods in Engineering 78, nr 7 (14.05.2009): 757–78. http://dx.doi.org/10.1002/nme.2503.
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Tiwari, Sanat, Vikram Dharodi, Amita Das, Predhiman Kaw i Abhijit Sen. "Kelvin-Helmholtz instability in dusty plasma medium: Fluid and particle approach". Journal of Plasma Physics 80, nr 6 (14.07.2014): 817–23. http://dx.doi.org/10.1017/s0022377814000397.
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The Kelvin-Helmholtz (KH) instability is studied in a two dimensional strongly coupled dusty plasma medium using a fluid approach as well as through a molecular dynamic (MD) simulation. For the fluid description the generalized hydrodynamic (GH) model which treats the strongly coupled dusty plasma as a visco-elastic fluid is adopted. For the MD studies the ensemble of particles are assumed to interact through a Yukawa potential. Both the approaches predict a stabilization of the KH growth rate with an increase in the strong coupling parameter. The present study also delineates the temporal evolution and the interaction of transverse shear waves with the collective dynamics of the dusty plasma medium within the framework of both these approaches.
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Haq, Mazhar Ul, Zhao Gang, Zhuang Zhi Sun i S. M. Aftab. "Force Analysis of IPMC Actuated Fin and Wing Assembly of a Micro Scanning Device through Two-Way Fluid Structure Interaction Approach". International Journal of Engineering Research in Africa 21 (grudzień 2015): 19–32. http://dx.doi.org/10.4028/www.scientific.net/jera.21.19.
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In this paper, a methodology is presented to perform force analysis of wing and fin assembly of a micro fish like device through strongly coupled two-way fluid structure interaction approach. The scanning device operates underwater and is towed by a surface vessel through a tow cable. Device fins are actuated by ionic polymer metal composite (IPMC) actuators, an EAP actuator. Fins act as riser, depressor and stabiliser against roll motion of the device. During tow, wing and fin assembly of the device come under hydrodynamic forces. These forces are influenced by fin displacement under IPMC actuation and wing's angle of attack for same towing conditions. To fully investigate wing and fin assembly performance, we must consider the interaction between their structure and fluid (water) and model the coupling mechanism accurately for fluid structure interaction (FSI) analysis. To obtain an accurate prediction to the hydrodynamic forces on wing and fin assembly of the device, it is necessary to conduct dynamic analysis of the surrounding fluid by computational fluid dynamics (CFD). A numerical simulation of three dimensional model of the assembly is performed in ANSYS WORKBENCH by coupling transient structural and Fluid Flow (CFX) analysis systems. The objectives of this study are as follows: 1) To build an accurate three-dimensional CFD model of the wing and IPMC actuated fin 2) To quantify the lift and drag forces acting on the wing and their corresponding coefficients 3) To demonstrate the influence of wing's angle of attack and fin displacement on generation of lift and drag forces. The presented methodology is also applicable to self-propelled micro robots.
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Alharbi, A., I. Ballai, V. Fedun i G. Verth. "Slow magnetoacoustic waves in gravitationally stratified two-fluid plasmas in strongly ionized limit". Monthly Notices of the Royal Astronomical Society 501, nr 2 (12.12.2020): 1940–50. http://dx.doi.org/10.1093/mnras/staa3835.
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ABSTRACT The plasma dynamics at frequencies comparable with collisional frequency between various species has to be described in multifluid framework, where collisional interaction between particles is an important ingredient. In our study, we will assume that charged particles are strongly coupled, meaning that they form a single fluid that interacts with neutrals, therefore we will employ a two-fluid model. Here, we aim to investigate the evolutionary equation of slow sausage waves propagating in a gravitationally stratified flux tube in the two-fluid solar atmosphere in a strongly ionized limit using an initial value analysis. Due to the collisional interaction between massive particles (ions and neutrals), the governing equations are coupled. Solutions are sought in the strongly ionized limit and the density ratio between neutrals and charged particles is a small parameter. This limit is relevant to the upper part of the chromosphere. Our results show that slow sausage waves associated with charged particles propagate such that their possible frequency is affected by a cut-off due to the gravitational stratification. In contrast, for neutral acoustic waves the cut-off value applies on their wavelength and only small wavelength waves are able to propagate. Slow modes associated with neutrals are driven by the collisional coupling with ions.
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Collis, J., D. L. Brown, M. E. Hubbard i R. D. O’Dea. "Effective equations governing an active poroelastic medium". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, nr 2198 (luty 2017): 20160755. http://dx.doi.org/10.1098/rspa.2016.0755.
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In this work, we consider the spatial homogenization of a coupled transport and fluid–structure interaction model, to the end of deriving a system of effective equations describing the flow, elastic deformation and transport in an active poroelastic medium. The ‘active’ nature of the material results from a morphoelastic response to a chemical stimulant, in which the growth time scale is strongly separated from other elastic time scales. The resulting effective model is broadly relevant to the study of biological tissue growth, geophysical flows (e.g. swelling in coals and clays) and a wide range of industrial applications (e.g. absorbant hygiene products). The key contribution of this work is the derivation of a system of homogenized partial differential equations describing macroscale growth, coupled to transport of solute, that explicitly incorporates details of the structure and dynamics of the microscopic system, and, moreover, admits finite growth and deformation at the pore scale. The resulting macroscale model comprises a Biot-type system, augmented with additional terms pertaining to growth, coupled to an advection–reaction–diffusion equation. The resultant system of effective equations is then compared with other recent models under a selection of appropriate simplifying asymptotic limits.
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MUKHERJEE, SWARNAVA, SHANMUKH SARODE, CHINMAYEE MUJUMDAR, LIZHI SHANG i ANDREA VACCA. "EFFECT OF DYNAMIC COUPLING ON THE PERFORMANCE OF PISTON PUMP LUBRICATING INTERFACES". MM Science Journal 2022, nr 3 (27.09.2022): 5783–90. http://dx.doi.org/10.17973/mmsj.2022_10_2022075.
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The energy efficiency and durability performance of axial piston machines are strongly affected by the tribological behavior of their lubricating interfaces. State-of-the-art approaches typically study these interface in isolation, neglecting possible reciprocal interactions between such interfaces. This paper presents an investigation of the mutual interaction between the piston/cylinder interface and the slipper/swashplate interface of a commercial axial piston pump. The proposed model can predict distributive fluid behavior in the lubricating gaps considering the effects of dynamics of the solid bodies, compressibility, mixed lubrication, elastic deformation, and cavitation. The dynamic coupling between the piston and the slipper is achieved by modeling the friction between the piston ball and slipper socket based on the force balance and the relative motion between the two bodies. The efficiencies predicted by this coupled model are compared to the ones obtained through the more established approach of solving the lubricating interfaces independently. The simulation results demonstrate the influence of the coupled physics on the lubricating interface performance, confirming the necessity of considering couple dynamics in lubricating interface numerical modeling.
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Guma, Giorgia, Philipp Bucher, Patrick Letzgus, Thorsten Lutz i Roland Wüchner. "High-fidelity aeroelastic analyses of wind turbines in complex terrain: fluid–structure interaction and aerodynamic modeling". Wind Energy Science 7, nr 4 (13.07.2022): 1421–39. http://dx.doi.org/10.5194/wes-7-1421-2022.
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Abstract. This paper shows high-fidelity fluid–structure interaction (FSI) studies applied to the research wind turbine of the WINSENT (Wind Science and Engineering in Complex Terrain) project. In this project, two research wind turbines are going to be erected in the south of Germany in the WindForS complex-terrain test field. The FSI is obtained by coupling the CFD URANS–DES code FLOWer and the multiphysics FEM solver Kratos Multiphysics, in which both beam and shell structural elements can be chosen to model the turbine. The two codes are coupled in both an explicit and an implicit way. The different modeling approaches strongly differ with respect to computational resources, and therefore the advantages of their higher accuracy must be correlated with the respective additional computational costs. The presented FSI coupling method has been applied firstly to a single-blade model of the turbine under standard uniform inflow conditions. It could be concluded that for such a small turbine, in uniform conditions a beam model is sufficient to correctly build the blade deformations. Afterwards, the aerodynamic complexity has been increased considering the full turbine with turbulent inflow conditions generated from real field data, in both flat and complex terrains. It is shown that in these cases a higher structural fidelity is necessary. The effects of aeroelasticity are then shown on the phase-averaged blade loads, showing that using the same inflow turbulence, a flat terrain is mostly influenced by the shear, while the complex terrain is mostly affected by low-velocity structures generated by the forest. Finally, the impact of aeroelasticity and turbulence on the damage equivalent loading (DEL) is discussed, showing that flexibility reduces the DEL in the case of turbulent inflow, acting as a damper that breaks larger cycles into smaller ones.
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Sciberras, Thomas, Marija Demicoli, Ivan Grech, Bertram Mallia, Pierluigi Mollicone i Nicholas Sammut. "Thermo-Mechanical Fluid–Structure Interaction Numerical Modelling and Experimental Validation of MEMS Electrothermal Actuators for Aqueous Biomedical Applications". Micromachines 14, nr 6 (17.06.2023): 1264. http://dx.doi.org/10.3390/mi14061264.
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Recent developments in MEMS technologies have made such devices attractive for use in applications that involve precision engineering and scalability. In the biomedical industry, MEMS devices have gained popularity in recent years for use as single-cell manipulation and characterisation tools. A niche application is the mechanical characterisation of single human red blood cells, which may exhibit certain pathological conditions that impart biomarkers of quantifiable magnitude that are potentially detectable via MEMS devices. Such applications come with stringent thermal and structural specifications wherein the potential device candidates must be able to function with no exceptions. This work presents a state-of-the-art numerical modelling methodology that is capable of accurately predicting MEMS device performance in various media, including aqueous ones. The method is strongly coupled in nature, whereby thermal as well as structural degrees of freedom are transferred to and from finite element and finite volume solvers at every iteration. This method therefore provides MEMS design engineers with a reliable tool that can be used in design and development stages and helps to avoid total reliability on experimental testing. The proposed numerical model is validated via a series of physical experiments. Four MEMS electrothermal actuators with cascaded V-shaped drivers are presented. With the use of the newly proposed numerical model as well as the experimental testing, the MEMS devices’ suitability for biomedical applications is confirmed.
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Schmid, P. J., i E. de Langre. "Transient Growth Before Coupled-Mode Flutter". Journal of Applied Mechanics 70, nr 6 (1.11.2003): 894–901. http://dx.doi.org/10.1115/1.1631591.
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Transient growth of energy is known to occur even in stable dynamical systems due to the non-normality of the underlying linear operator. This has been the object of growing attention in the field of hydrodynamic stability, where linearly stable flows may be found to be strongly nonlinearly unstable as a consequence of transient growth. We apply these concepts to the generic case of coupled-mode flutter, which is a mechanism with important applications in the field of fluid-structure interactions. Using numerical and analytical approaches on a simple system with two degrees-of-freedom and antisymmetric coupling we show that the energy of such a system may grow by a factor of more than 10, before the threshold of coupled-mode flutter is crossed. This growth is a simple consequence of the nonorthogonality of modes arising from the nonconservative forces. These general results are then applied to three cases in the field of flow-induced vibrations: (a) panel flutter (two-degrees-of-freedom model, as used by Dowell) (b) follower force (two-degrees-of-freedom model, as used by Bamberger) and (c) fluid-conveying pipes (two-degree-of-freedom model, as used by Benjamin and Pai¨doussis) for different mass ratios. For these three cases we show that the magnitude of transient growth of mechanical energy before the onset of coupled-mode flutter is substantial enough to cause a significant discrepancy between the apparent threshold of instability and the one predicted by linear stability theory.
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Nguyen, Anh-Tu. "A numerical research on the interaction between underwater explosion bubble and deformable structure using CEL technique". EUREKA: Physics and Engineering, nr 1 (19.01.2023): 134–51. http://dx.doi.org/10.21303/2461-4262.2023.002637.
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The dynamic process of an underwater explosion (UNDEX) bubble in the vicinity of deformable structures is a complex phenomenon that has been studied by many researchers. The dynamic process of a UNDEX bubble is a complex transient problem that results in a highly distorted bubble and large deformation of the structure. The previous work has introduced various solutions for studying the interaction between the UNDEX bubble and deformable structure. The interaction between the bubble and nearby structures has been widely solved by the combination of the boundary element method (BEM) and the finite element method (FEM). However, this couple requires tight time-step controlling, long-time analysis, and large computer resources. Furthermore, this combination is not widely used as the FEM code in commercially available software for solving UNDEX bubble problems. This paper presents a coupled Eulerian-Lagrangian (CEL) approach in commercial software to deal with the fluid-structure interaction (FSI). The numerical model of a UNDEX bubble is first developed and verified by comparing results with experimental, BEM, and empirical data. Then both bubble behavior and structural deformation are examined in various case studies. The numerical results show that the stiffness of the structure has strongly influenced the bubble behavior and the water jet development. The pressure pulse becomes significantly large as the bubble collapse. Besides, this numerical approach also can reproduce crucial phenomena of a UNDEX bubble, such as the whipping effect and water jet attacks. Although the numerical model is developed using simplified boundary conditions, the proposed approach shows the feasibility of simulating the important features of a UNDEX bubble process as well as the response of nearby structures.
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Wiesenberger, M., i M. Held. "Long-wavelength closures for collisional and neutral interaction terms in gyro-fluid models". Journal of Physics: Conference Series 2397, nr 1 (1.12.2022): 012015. http://dx.doi.org/10.1088/1742-6596/2397/1/012015.
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Abstract A collisional gyro-fluid model is presented. The goal of the model is edge and scrape-off layer turbulence. The emphasize in the model derivation heavily lies on ”implementability” with today’s numerical methods. This translates to an avoidance of infinite sums, strongly coupled equations in time and intricate elliptic operator functions. The resulting model contains the four moments density, parallel momentum, perpendicular pressure and parallel energy and is closed by a polarisation equation and parallel Ampere law. The central ingredient is a collisional long-wavelength closure that relies on a drift-fluid gyro-fluid correspondence principle. In this way the extensive literature on fluid collisions can be incorporated into the model including sources, plasma-neutral interactions and scattering collisions. Even though this disregards the characteristic finite Larmor radius terms in the collisional terms the resulting model is at least as accurate as the corresponding drift-fluid model in these terms. Furthermore, the model does enjoy the benefits of an underlying variational principle in an energy-momentum theorem and an inherent symmetry in moment equations with regards to multiple ion species. Consistent particle drifts as well as finite Larmor radius corrections and high amplitude effects in the advection and polarization terms are further characteristics of the model. Extensions and improvements like short-wavelength expressions, a trans-collisional closure scheme for the low-collisionality regime or zeroth order potential must be added at a later stage.
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Cioncolini, Andrea, Mostafa R. A. Nabawy, Jorge Silva-Leon, Joseph O’Connor i Alistair Revell. "An Experimental and Computational Study on Inverted Flag Dynamics for Simultaneous Wind–Solar Energy Harvesting". Fluids 4, nr 2 (11.05.2019): 87. http://dx.doi.org/10.3390/fluids4020087.
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This paper presents results from experiments and simplified numerical simulations on the flow-induced dynamics and power generation of inverted flags that combine flexible piezoelectric strips with photovoltaic cells to simultaneously harvest kinetic wind energy and solar radiant energy. Experiments were conducted in a wind tunnel under controlled wind excitation and light exposure, focusing in particular on the dynamics and power generation of the inverted flag harvester. Numerical simulations were carried out using a lattice-Boltzmann fluid solver coupled with a finite element structural solver via the immersed-boundary method, focusing in particular on minimizing the simulation run time. The power generated during the tests shows that the proposed inverted flag harvester is a promising concept, capable of producing enough power (on the order of 1 mW) to supply low-power electronic devices in a range of applications where distributed power generation is needed. Notwithstanding key simplifications implemented in the numerical model to achieve a fast execution, simulations and measurements are in good agreement, confirming that the lattice-Boltzmann method is a viable and time-effective alternative to classic Navier–Stokes-based solvers when dealing with strongly coupled fluid–structure interaction problems characterized by large structural displacements.
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THIAMOVA, G., i D. J. ROWE. "PERSISTENCE OF ROTATIONAL STRUCTURE IN NUCLEI AND QUASI-DYNAMICAL SYMMETRY". International Journal of Modern Physics E 15, nr 08 (listopad 2006): 1741–50. http://dx.doi.org/10.1142/s0218301306005551.
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The existence of quasi-dynamical symmetry (QDS) in physical systems and its significance for understanding the persistence of rotational structure in nuclei is explained in terms of the mathematical concept of an embedded representation. We consider the spectra obtained by coupling two SU (3) irreps by means of a quadrupole-quadrupole interaction. For a particular large value of this interaction, the two irreps combine to form a single (strongly-coupled) irrep while for zero interaction the weakly-coupled results are mixtures of many irreps. A notable result is the persistence of the rotor character of the low-energy states for a wide range of the interaction strength which can be explained by coherent mixing of SU (3) irreps. Such a coherent mixing of representations is an indication that the model has a QDS. Also notable is the fact that, for very weak interaction strengths, the rotational states of the yrast band approach those of a vibrational sequence while the B( E 2) transition strengths remain close to those of an axially symmetric rotor.
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Sciberras, Thomas, Marija Demicoli, Ivan Grech, Bertram Mallia, Pierluigi Mollicone i Nicholas Sammut. "Coupled Finite Element-Finite Volume Multi-Physics Analysis of MEMS Electrothermal Actuators". Micromachines 13, nr 1 (22.12.2021): 8. http://dx.doi.org/10.3390/mi13010008.
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Microelectromechanical systems (MEMS) are the instruments of choice for high-precision manipulation and sensing processes at the microscale. They are, therefore, a subject of interest in many leading industrial and academic research sectors owing to their superior potential in applications requiring extreme precision, as well as in their use as a scalable device. Certain applications tend to require a MEMS device to function with low operational temperatures, as well as within fully immersed conditions in various media and with different flow parameters. This study made use of a V-shaped electrothermal actuator to demonstrate a novel, state-of-the-art numerical methodology with a two-way coupled analysis. This methodology included the effects of fluid–structure interaction between the MEMS device and its surrounding fluid and may be used by MEMS design engineers and analysts at the design stages of their devices for a more robust product. Throughout this study, a thermal–electric finite element model was strongly coupled to a finite volume model to incorporate the spatially varying cooling effects of the surrounding fluid (still air) onto the V-shaped electrothermal device during steady-state operation. The methodology was compared to already established and accepted analysis methods for MEMS electrothermal actuators in still air. The maximum device temperatures for input voltages ranging from 0 V to 10 V were assessed. During the postprocessing routine of the two-way electrothermal actuator coupled analysis, a spatially-varying heat transfer coefficient was evident, the magnitude of which was orders of magnitude larger than what is typically applied to macro-objects operating in similar environmental conditions. The latter phenomenon was correlated with similar findings in the literature.
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Perczel, Andrås, Raymond Daudel, Jånos G. Ångyån i Imre G. Csizmadia. "A study on the backbone/side-chain interaction in N-formyl-(L)serineamide". Canadian Journal of Chemistry 68, nr 10 (1.10.1990): 1882–88. http://dx.doi.org/10.1139/v90-291.
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The N-formyl-serineamide (For-Ser-NH2), a model diamide for the conformational behaviour of the protein backbone at serine residue, has been gradient optimized for selected conformations at the abinitio 3-21G level. Previous molecular mechanics ECEPP/2 calculations suggested that the optimal side-chain (χ1, χ2) and backbone [Formula: see text] conformations are strongly coupled, due to intramolecular H-bonding formed between the side-chain hydroxyl group and the amide moiety. Four different side-chain geometries (I–IV) were considered at each of the four backbone conformations (α, β, β′, γ) giving a total 16 different critical points on the coupled [Formula: see text] surface. The very fact that upon changing the [Formula: see text] values the global minimum of (χ1, χ2) surface was shifted indicated clearly that the two subspaces are strongly coupled. The present theoretical results were compared to experimental peptide and protein geometries taken from the Cambridge Structure Database and from the Brookhaven Protein Data Bank, respectively. Keywords: conformation of a serinediamide, backbone side-chain interactions, topological analysis of potential energy surfaces, abinitio calculations.
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Chen, Lu, Tianzhengxiong Deng, Helezi Zhou, Zhigao Huang, Xiongqi Peng i Huamin Zhou. "A Numerical Simulation Method for the One-Step Compression-Stamping Process of Continuous Fiber Reinforced Thermoplastic Composites". Polymers 13, nr 19 (24.09.2021): 3237. http://dx.doi.org/10.3390/polym13193237.
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Continuous fiber reinforced thermoplastic (CFRTP) composites have many advantages, such as high strength, high stiffness, shorter cycle, time and enabling the part consolidation of structural components. However, the mass production of the CFRTP parts is still challenging in industry and simulations can be used to better understand internal molding mechanisms. This paper proposes a three-dimensional simulation method for a one-step compression-stamping process which can conduct thermoplastic compression molding and continuous fiber reinforced thermoplastic composite stamping forming in one single mold, simultaneously. To overcome the strongly coupled non-isothermal moving boundary between the polymer and the composites, arbitrary Lagrangian–Eulerian based Navier–Stokes equations were applied to solve the thermoplastic compression, and a fiber rotation based objective stress rate model was used to solve for the composite stamping. Meanwhile, a strongly coupled fluid structure interaction framework with dual mesh technology is proposed to address the non-isothermal moving boundary issue between the polymer and the composites. This simulation method was compared against the experimental results to verify its accuracy. The polymer flow fronts were measured at different molding stages and the error between simulation and experiment was within 3.5%. The final composites’ in-plane deformation error was less than 2.5%. The experiment shows that this work can accurately simulate the actual molding process.
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Tian, Wanyi, Lingyun Yao i Li Li. "A Coupled Smoothed Finite Element-Boundary Element Method for Structural-Acoustic Analysis of Shell". Archives of Acoustics 42, nr 1 (1.03.2017): 49–59. http://dx.doi.org/10.1515/aoa-2017-0006.
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Abstract Nowadays, the finite element method (FEM) - boundary element method (BEM) is used to predict the performance of structural-acoustic problem, i.e. the frequency response analysis, modal analysis. The accuracy of conventional FEM/BEM for structural-acoustic problems strongly depends on the size of the mesh, element quality, etc. As element size gets greater and distortion gets severer, the deviation of high frequency problem is also clear. In order to improve the accuracy of structural-acoustic problem, a smoothed finite-element/boundary-element coupling procedure (SFEM/BEM) is extended to analyze the structural-acoustic problem consisting of a shell structure interacting with the cavity in this paper, in which the SFEM and boundary element method (BEM) models are used to simulate the structure and the fluid, respectively. The governing equations of the structural-acoustic problems are established by coupling the SFEM for the structure and the BEM for the fluid. The solutions of SFEM are often found to be much more accurate than those of the FEM model. Based on its attractive features, it was decided in the present work to extend SFEM further for use in structural-acoustic analysis by coupling it with BEM, the present SFEM/BEM is implemented to predict the vehicle structure-acoustic frequency response analysis, and two numerical experiments results show that the present method can provide more accurate results compared with the standard FEM/BEM using the same mesh. It indicates that the present SFEM/BEM can be widely applied to solving many engineering noise, vibration and harshness (NVH) problems with more accurate solutions.
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Buczkowski, Daniel, Szymon Zymelka i Grzegorz Nowak. "Experimental and Numerical Studies on the Development of Hysteresis in a Shock Absorber with a Shim Disc Valve". International Journal of Automotive and Mechanical Engineering 19, nr 2 (28.06.2022): 9747–58. http://dx.doi.org/10.15282/ijame.19.2.2022.10.0752.
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The paper describes the observed occurrence of hysteresis of the characteristic curve of a shock absorber valve. The phenomenon has an impact on the asymmetry of the damping force characteristic and should be taken into account when modelling the valve operation. The aim of the investigations was to determine the factors generating the phenomenon and establish the relationships between these factors and the hysteresis size. Tests were carried out on a stand intended for valve measurements in isolated conditions. A strongly coupled Fluid-Structure Interaction numerical model was also created to simulate the valve operation in selected conditions. The results indicate that the hysteresis loop occurrence is mainly due to the conditions of the valve disc stack preload in the process of its composition and, consequently, to the friction between the valve elements. Having an impact on the contact between discs and on the disc stack overall structure, they affect the hysteresis field significantly. The testing results confirm the supposition that hysteresis is not due to the phenomena related to the conditions of the flow through the valve.
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Banihashemi, Saeideh, James T. Kirby, Fengyan Shi i Zhifei Dong. "WAVES AND STRONGLY SHEARED CURRENTS: EXTENSIONS TO COASTAL OCEAN MODELS". Coastal Engineering Proceedings, nr 36 (30.12.2018): 40. http://dx.doi.org/10.9753/icce.v36.currents.40.
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Significant progress has been made in the numerical modeling of wave-current interaction during the past decade. Typical coastal circulation and wave models, however, still only employ theoretical formulations which take depth-uniform mean flows into account, with realistic, non-uniform flows treated as being depth uniform through some chosen averaging procedure. Depending on the choice of average over depth, significant errors may arise in the estimation of properties such as group velocity and action density in realistic conditions. These errors, in turn, are fed back into the circulation model through incorrect representation of the vertical structure of wave forcing. A new framework for wave-current interaction theory for strongly sheared mean flows has been developed using vortex force formalism by Dong (2016). The resulting formulation leads to a conservation law for wave action identical to that of Voronovich (1976), and to expressions for wave-averaged forces in the Craik-Leibovich vortex force formalism. In this study, we are completing the development of a coupled NHWAVE/SWAN which implements the wave forcing formulation of Dong (2016) in a wave-averaged version of the non-hydrostatic model NHWAVE (Ma et al., 2012). The SWAN model is also being extended to incorporate a better representation of frequency and direction-dependent group velocity and intrinsic frequency in the neighborhood of the spectral peak, thus improving on the present practice of using quantities evaluated only at the spectral peak. The resulting model is being tested against field data collected in several recent experiments involving strong, vertically sheared currents in river mouths or straits.
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Shi, Wenhao, i Tianhong Yang. "A Coupled Nonlinear Flow Model for Particle Migration and Seepage Properties of Water Inrush through Broken Rock Mass". Geofluids 2020 (9.09.2020): 1–14. http://dx.doi.org/10.1155/2020/1230542.
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A large number of statistics indicate that broken rock mass always transforms into a flowing channel and leads to water inrush disasters in mining engineering, such as fault, karst, and strongly weathered rock mass. During the process of water inrush, the structure of the broken rock mass is constantly changing due to seepage erosion under high-velocity flow. Therefore, it is of vital importance to quantitatively evaluate the flow behavior of the water inrush related to the seepage erosion in order to prevent or reduce the risks. This study described a coupled nonlinear flow model, which couples the high-velocity seepage, the small particle migration, and the evolution of the broken rock mass structure. The model was verified firstly for simulation of nonlinear flow behavior by comparing with the traditional one. Then, the proposed model was used to simulate the evolution of particle migration and seepage properties of the water inrush through broken rock mass by a numerical case. The simulation results generally agree well with the existing experimental results. The simulations indicate that small particle migration causes the unstable characteristics of the seepage and the heterogeneity properties of the broken rock mass, which lead to the nonlinear flow behavior of the water inrush in both time and space. From a different perspective, it also indicates that the proposed model is capable of simulating the interaction of high-velocity seepage, small particle migration, and evolution of broken rock mass structure in the process of water inrush.
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Sváček, P., i J. Horáček. "Numerical Simulation of Glottal Flow in Interaction with Self Oscillating Vocal Folds: Comparison of Finite Element Approximation with a Simplified Model". Communications in Computational Physics 12, nr 3 (wrzesień 2012): 789–806. http://dx.doi.org/10.4208/cicp.011010.280611s.
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AbstractIn this paper the numerical method for solution of an aeroelastic model describing the interactions of air flow with vocal folds is described. The flow is modelled by the incompressible Navier-Stokes equations spatially discretized with the aid of the stabilized finite element method. The motion of the computational domain is treated with the aid of the Arbitrary Lagrangian Eulerian method. The structure dynamics is replaced by a mechanically equivalent system with the two degrees of freedom governed by a system of ordinary differential equations and discretized in time with the aid of an implicit multistep method and strongly coupled with the flow model. The influence of inlet/outlet boundary conditions is studied and the numerical analysis is performed and compared to the related results from literature.
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Bahrami, Saeed, i Mahmood Norouzi. "Hemodynamic impacts of hematocrit level by two-way coupled FSI in the left coronary bifurcation". Clinical Hemorheology and Microcirculation 76, nr 1 (15.10.2020): 9–26. http://dx.doi.org/10.3233/ch-200854.
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Cardiovascular disease is now under the influence of several factors that encourage researchers to investigate the flow of these vessels. Oscillation influences the blood circulation in the volume of red blood cells (RBC) strongly. Therefore, in this study, its effects have been considered on hemodynamic parameters in the elastic wall and coronary bifurcation. In this study, a 3D geometry of non-Newtonian and pulsatile blood circulation is considered in the left coronary artery bifurcation. The Casson model with various hematocrits is analyzed in elastic and rigid walls. The wall shear stress (WSS) cannot show the stenosis artery alone, therefore, the oscillatory shear index (OSI) is represented as a hemodynamic parameter of WSS individually of time. The results are determined using two-way fluid-structure interaction (FSI) coupling method using an arbitrary Lagrangian-Eulerian method. The most prominent difference in velocity happened in the bifurcation and at hematocrit 30 with yield stress 6.59E-04 Pa. The backflow and vortex flow in the LCx branch grown with increasing shear rates. The likelihood of plaque generation at the ending of the LM branch is observed in hematocrits 10 and 20, while the WSS magnitude is normal in the hematocrit 60 with the greatest yield stress in the bifurcation. The shear stress among the rigid and elastic models is the highest at the ending of the LM branch. The wall shear stress magnitude among the models decreased at most of 24.49% by dividing the flow. Time-independent results for models showed that there is the highest value of OSI at the bifurcation, which then quickly dropped.
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COOPER, A. J., i PETER W. CARPENTER. "The stability of rotating-disc boundary-layer flow over a compliant wall. Part 1. Type I and II instabilities". Journal of Fluid Mechanics 350 (10.11.1997): 231–59. http://dx.doi.org/10.1017/s0022112097006976.
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A theoretical study into the effects of wall compliance on the stability of the rotating-disc boundary layer is described. A single-layer viscoelastic wall model is coupled to a sixth-order system of fluid stability equations which take into account the effects of viscosity, Coriolis acceleration, and streamline curvature. The coupled system of equations is integrated numerically by a spectral Chebyshev-tau technique.Travelling and stationary modes are studied and wall compliance is found to greatly increase the complexity of the eigenmode spectrum. It is effective in stabilizing the inviscid Type I (or cross-flow) instability. The effect on the viscous (Type II) eigenmode is more complex and can be strongly destabilizing. An analysis of the energy flux indicates that this destabilization arises as a result of a large degree of energy production by viscous stresses at the wall/flow interface.The Type I and II instabilities are shown to be negative and positive energy waves respectively. The co-existence of eigenmodes of opposite energy type indicates the possibility of modal interaction and coalescence. It is found that, compared with the rigid disc, wall compliance promotes the interaction and coalescence of the Type I and II eigenmodes. There is an associated strong instability which appears to be characterized by marked horizontal motion of the compliant surface. Modal coalescence is interpreted physically as producing local algebraic growth which could advance the onset of nonlinear effects.
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Zhang, Liping, i Thomas L. Delworth. "Analysis of the Characteristics and Mechanisms of the Pacific Decadal Oscillation in a Suite of Coupled Models from the Geophysical Fluid Dynamics Laboratory". Journal of Climate 28, nr 19 (29.09.2015): 7678–701. http://dx.doi.org/10.1175/jcli-d-14-00647.1.
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Abstract North Pacific decadal oceanic and atmospheric variability is examined in a suite of coupled climate models developed at the Geophysical Fluid Dynamics Laboratory (GFDL). The models have ocean horizontal resolutions ranging from 1° to 0.1° and atmospheric horizontal resolutions ranging from 200 to 50 km. In all simulations the dominant pattern of decadal-scale sea surface temperature (SST) variability over the North Pacific is similar to the observed Pacific decadal oscillation (PDO). Simulated SST anomalies in the Kuroshio–Oyashio Extension (KOE) region exhibit a significant spectral peak at approximately 20 yr. Sensitivity experiments are used to show that (i) the simulated PDO mechanism involves extratropical air–sea interaction and oceanic Rossby wave propagation; (ii) the oscillation can exist independent of interactions with the tropics, but such interactions can enhance the PDO; and (iii) ocean–atmosphere feedback in the extratropics is critical for establishing the approximately 20-yr time scale of the PDO. The spatial pattern of the PDO can be generated from atmospheric variability that occurs independently of ocean–atmosphere feedback, but the existence of a spectral peak depends on active air–sea coupling. The specific interdecadal time scale is strongly influenced by the propagation speed of oceanic Rossby waves in the subtropical and subpolar gyres, as they provide a delayed feedback to the atmosphere. The simulated PDO has a realistic association with precipitation variations over North America, with a warm phase of the PDO generally associated with positive precipitation anomalies over regions of the western United States. The seasonal dependence of this relationship is also reproduced by the model.
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Zhang, Hai Tao, Hiromi Nagaum, Yu Bo Zuo i Jian Zhong Cui. "Coupled Modeling of Electromagnetic Field, Fluid Flow, Heat Transfer and Solidification during Conventional DC Casting and Low Frequency Electromagnetic Casting of 7XXX Aluminum Alloys". Advanced Materials Research 15-17 (luty 2006): 18–23. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.18.
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A comprehensive mathematical model has been developed to describe the interaction of the multiple physics fields during the conventional DC casting and LFEC (low frequency electromagnetic casting) process. The model is based on a combination of the commercial finite element package ANSYS and the commercial finite volume package FLUENT, with the former for the calculation of the electromagnetic field and the latter for the calculation of the magnetic driven fluid flow, heat transfer and solidification. Moreover, the model has been verified against the temperature measurements obtained from two 7XXX aluminum alloy billets of 200mm diameter, cast during the conventional DC casting and the LFEC casting processes. In addition, a measurement of the sump shape of the billets were carried out by using addition melting metal of Al-30%Cu alloy into the billets during casting process. There was a good agreement between the calculated results and the measured results. Further, comparison of the calculated results during the LFEC process with that during the conventional DC casting process indicated that velocity patterns, temperature profiles and the sump depth are strongly modified by the application of a low frequency electromagnetic field during the DC casting.
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Ritschel, Thomas, Lutz Zülicke i Philip J. Kuntz. "Cationic Van-der-Waals Complexes: Theoretical Study of Ar2H+ Structure and Stability". Zeitschrift für Physikalische Chemie 218, nr 4 (1.04.2004): 377–90. http://dx.doi.org/10.1524/zpch.218.4.377.29196.
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AbstractThe electronic and geometric structure, stability and molecular properties of the cationic van-der-Waals complex Ar2H+ in its ground electronic state are studied by means of two ab-initio quantum-chemical approaches: conventional configuration interaction (multi-reference and coupled-cluster methods) and a diatomics-in-molecules model with ab-initio input data. To ensure consistency between the two approaches, one and the same one-electron atomic basis set (aug-cc-pVTZ by Dunning) is employed in both. The topography of the ground-state potential-energy surface is examined with respect to the nature of the binding and the stability of structures corresponding to stationary points. In accordance with most earlier theoretical work, there are two local minima at linear arrangements: a strongly bound centro-symmetric moiety, (Ar–H–Ar)+, and a weakly bound van-der-Waals complex, Ar···ArH+. These are separated by a low barrier. Only the centro-symmetric molecule is significantly stable (De = 0.68eV) against fragmentation into Ar + ArH+ and should have structural and dynamical relevance. A fairly simple diatomics-in-molecules model taking into account only the few lowest electronic fragment states yields a qualitatively correct description of the ground state but shows quantitative deviations from the more accurate configuration-interaction data in detail. Nevertheless, it should provide a good starting point for the treatment of larger complexes ArnH+ with n > 2.
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Westcott, Gregory, Annette R. Grilli, Stephan Grilli, James T. Kirby i Fengyan Shi. "INDIVIDUAL WAVE EFFECTS ON COASTAL STRUCTURE DAMAGE DURING WINDSTORMS". Coastal Engineering Proceedings, nr 36 (30.12.2018): 14. http://dx.doi.org/10.9753/icce.v36.structures.14.
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In hazard assessment studies that evaluate the damage caused to coastal structures by windstorm-generated surge and waves, the standard approach has been to estimate structural loading by applying phase-averaged wave propagation models (e.g., SWAN, STWAVE) and storm surge models (e.g., ADCIRC), coupled or not with each other. Bare-earth “Digital Elevation Models†(DEMs) have typically been used as a basis for model grid development, with sometimes empirical adjustments being made to beach profiles or dune crest levels to account for storm-induced erosion. In recent work, the latter approach has been improved by including real time morphodynamic changes in simulations, using models such as XBeach (e.g., Schambach 2017; Schambach et al., 2017), which are still based on the wave action conservation equation, including semi-empirical parameterizations of wave breaking and many formulations based on linear wave theory (e.g., phase/group velocity, radiation stresses,…), as well as low-order wave-wave interaction terms. Finally, structural damage has typically been estimated based on empirical damage curves, developed based on field surveys, that use flow depth and controlling wave crest height as inputs (e.g., Grilli et al., 2017). Neglected in this modeling approach, however, are dynamic set-up and runup effects, as well as strongly nonlinear wave interactions that occur near and in the surf and swash zones.
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Holley, David C., i Michael P. Kavanaugh. "Interactions of alkali cations with glutamate transporters". Philosophical Transactions of the Royal Society B: Biological Sciences 364, nr 1514 (31.10.2008): 155–61. http://dx.doi.org/10.1098/rstb.2008.0246.
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The transport of glutamate is coupled to the co-transport of three Na + ions and the countertransport of one K + ion. In addition to this carrier-type exchange behaviour, glutamate transporters also behave as chloride channels. The chloride channel activity is strongly influenced by the cations that are involved in coupled flux, making glutamate transporters representative of the ambiguous interface between carriers and channels. In this paper, we review the interaction of alkali cations with glutamate transporters in terms of these diverse functions. We also present a model derived from electrostatic mapping of the predicted cation-binding sites in the X-ray crystal structure of the Pyrococcus horikoshii transporter Glt Ph and in its human glutamate transporter homologue EAAT3. Two predicted Na + -binding sites were found to overlap precisely with the Tl + densities observed in the aspartate-bound complex. A novel third site predicted to favourably bind Na + (but not Tl + ) is formed by interaction with the substrate and the occluding HP2 loop. A fourth predicted site in the apo state exhibits selectivity for K + over both Na + and Tl + . Notably, this K + site partially overlaps the glutamate-binding site, and their binding is mutually exclusive. These results are consistent with kinetic and structural data and suggest a plausible mechanism for the flux coupling of glutamate with Na + and K + ions.
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Gautam, Manjeet Singh, Hitender Khatri i K. Vinod. "Interplay of neutron transfer and collective degrees of freedom in the fusion dynamics of 16O +76Ge and 18O +74Ge reactions". International Journal of Modern Physics E 28, nr 01n02 (luty 2019): 1950006. http://dx.doi.org/10.1142/s021830131950006x.
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This work examined the fusion dynamics of [Formula: see text] and [Formula: see text] reactions within the framework of the static Woods–Saxon potential model, the energy dependent Woods–Saxon potential (EDWSP) model and coupled channel formulation. The effects of inelastic surface excitations, static deformation of colliding pairs and /or neutron transfer channels on fusion process are investigated through the coupled channel method. The calculations based upon static Woods–Saxon potential in conjunction with one-dimensional Wong formula strongly under predict the fusion data of [Formula: see text] and [Formula: see text] reactions at sub-barrier energies. However, such discrepancies are removed if one uses couplings to nuclear structure degrees of freedom of reacting nuclei. The coupled channel calculations obtained by considering the vibrational nature of the colliding nuclei fairly reproduce the fusion data of [Formula: see text] reactions. For this reaction, the neutron transfer channels, which are expected to influence strongly the fusion yields at below barrier energies, in reality contribute very weakly to fusion process. While in case of [Formula: see text] reaction, the consideration of vibrational couplings as well as the rotational couplings for target provides a reasonable explanation to the fusion cross-section data at near and above barrier energies. In distinction, the energy dependence in the nucleus–nucleus potential causes barrier modulation effects and subsequently modifies the barrier profile of the interaction barrier in such a way that the effective fusion barrier between the colliding pair reduces. This ultimately brings larger fusion cross-sections over the outcomes of one-dimensional barrier penetration model and the EDWSP model based calculations appreciably explained the fusion dynamics of chosen reaction at energy spanning around the Coulomb barrier. Both models (EDWSP and coupled channel model) lead to barrier lowering effects and modeled quantum tunneling in different way, henceforth, adequately explore the fusion dynamics of the studied reactions in near and above barrier energy regions.
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Andronikos, Theologos, George Papadakis, Vasilis Riziotis i Spyros Voutsinas. "Revising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development". Applied Sciences 11, nr 21 (24.10.2021): 9935. http://dx.doi.org/10.3390/app11219935.
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The interaction of a helicopter rotor with the ground in hover flight is addressed numerically using a hybrid Eulerian–Lagrangian CFD model. When a helicopter takes off or lands, its wake interferes with the ground. This interaction, depending on the height-to-rotor diameter ratio, causes the altering of the rotor loading and performance as compared to the unconstrained case and gives rise to the development of a complex outwash flow field in the surrounding of the helicopter. The present study aims to characterize the interactional phenomena occurring in the early stages of the rotor wake development and in particular the interference of the starting vortex with the ground boundary layer and the effect of this interaction in the motion of the vortex in the rotor outwash flow. The hybrid CFD method employed combines a standard URANS compressible finite volume solver, the use of which is restricted to confined grids around solid bodies, and a Lagrangian approximation of the entire flow field in which conservation equations are solved in their material form, disctretized using particle representation of the flow quantities. The two methods are strongly coupled to each other through an appropriate iterative scheme. The main advantage of the proposed methodology is that it can conveniently handle complex configurations with several bodies that move independently from one another, with affordable computational cost. In this paper, thrust coefficient predictions of the hybrid model are compared to predictions of a free wake code and to experimental data indicating that consistent prediction of the rotor load requires the inclusion of the ground boundary layer in the analysis. Moreover, detailed comparisons of the rotor wake evolution predicted by the hybrid model are presented.
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Ghosh, Purusottam, Partha Konar, Abhijit Kumar Saha i Sudipta Show. "Self-interacting freeze-in dark matter in a singlet doublet scenario". Journal of Cosmology and Astroparticle Physics 2022, nr 10 (1.10.2022): 017. http://dx.doi.org/10.1088/1475-7516/2022/10/017.
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Abstract We examine the non-thermal production of dark matter in a scalar extended singlet doublet fermion model where the lightest admixture of the fermions constitutes a suitable dark matter candidate. The dark sector is non-minimal with the MeV scale singlet scalar, which is stable in the Universe lifetime and can mediate the self-interaction for the multi-GeV fermion dark matter mitigating the small scale structure anomalies of the Universe. If the dark sector is strongly coupled to yield a velocity dependent large self-interaction cross section, it undergoes internal dark thermal equilibrium after freeze-in production. We essentially end up with suppressed relic abundance for the fermion dark matter in a traditional radiation dominated Universe. In contrast, the presence of a modified cosmological phase in the early era drives the fermion dark matter to satisfy nearly the whole amount of observed relic. It also turns out that the assumption of an unconventional cosmological history can allow the GeV scale dark matter to be probed at LHC from displaced vertex signature with improved sensitivity.
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Tang, Jizhou, Kan Wu, Lihua Zuo, Lizhi Xiao, Sijie Sun i Christine Ehlig–Economides. "Investigation of Rupture and Slip Mechanisms of Hydraulic Fractures in Multiple-Layered Formations". SPE Journal 24, nr 05 (28.08.2019): 2292–307. http://dx.doi.org/10.2118/197054-pa.
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Summary Weak bedding planes (BPs) that exist in many tight oil formations and shale–gas formations might strongly affect fracture–height growth during hydraulic–fracturing treatment. Few of the hydraulic–fracture–propagation models developed for unconventional reservoirs are capable of quantitatively estimating the fracture–height containment or predicting the fracture geometry under the influence of multiple BPs. In this paper, we introduce a coupled 3D hydraulic–fracture–propagation model considering the effects of BPs. In this model, a fully 3D displacement–discontinuity method (3D DDM) is used to model the rock deformation. The advantage of this approach is that it addresses both the mechanical interaction between hydraulic fractures and weak BPs in 3D space and the physical mechanism of slippage along weak BPs. Fluid flow governed by a finite–difference methodology considers the flow in both vertical fractures and opening BPs. An iterative algorithm is used to couple fluid flow and rock deformation. Comparison between the developed model and the Perkins–Kern–Nordgren (PKN) model showed good agreement. I–shaped fracture geometry and crossing–shaped fracture geometry were analyzed in this paper. From numerical investigations, we found that BPs cannot be opened if the difference between overburden stress and minimum horizontal stress is large and only shear displacements exist along the BPs, which damage the planes and thus greatly amplify their hydraulic conductivity. Moreover, sensitivity studies investigate the impact on fracture propagation of parameters such as pumping rate (PR), fluid viscosity, and Young's modulus (YM). We investigated the fracture width near the junction between a vertical fracture and the BPs, the latter including the tensile opening of BPs and shear–displacement discontinuities (SDDs) along them. SDDs along BPs increase at the beginning and then decrease at a distance from the junction. The width near the junctions, the opening of BPs, and SDDs along the planes are directly proportional to PR. Because viscosity increases, the width at a junction increases as do the SDDs. YM greatly influences the opening of BPs at a junction and the SDDs along the BPs. This model estimates the fracture–width distribution and the SDDs along the BPs near junctions between the fracture tip and BPs and enables the assessment of the PR required to ensure that the fracture width at junctions and along intersected BPs is sufficient for proppant transport.
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Traverso, Sonia, Laura Elia i Michael Pusch. "Gating Competence of Constitutively Open CLC-0 Mutants Revealed by the Interaction with a Small Organic Inhibitor". Journal of General Physiology 122, nr 3 (11.08.2003): 295–306. http://dx.doi.org/10.1085/jgp.200308784.
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Opening of CLC chloride channels is coupled to the translocation of the permeant anion. From the recent structure determination of bacterial CLC proteins in the closed and open configuration, a glutamate residue was hypothesized to form part of the Cl−-sensitive gate. The negatively charged side-chain of the glutamate was suggested to occlude the permeation pathway in the closed state, while opening of a single protopore of the double-pore channel would reflect mainly a movement of this side-chain toward the extracellular pore vestibule, with little rearrangement of the rest of the channel. Here we show that mutating this critical residue (Glu166) in the prototype Torpedo CLC-0 to alanine, serine, or lysine leads to constitutively open channels, whereas a mutation to aspartate strongly slowed down opening. Furthermore, we investigated the interaction of the small organic channel blocker p-chlorophenoxy-acetic acid (CPA) with the mutants E166A and E166S. Both mutants were strongly inhibited by CPA at negative voltages with a >200-fold larger affinity than for wild-type CLC-0 (apparent KD at −140 mV ∼4 μM). A three-state linear model with an open state, a low-affinity and a high-affinity CPA-bound state can quantitatively describe steady-state and kinetic properties of the CPA block. The parameters of the model and additional mutagenesis suggest that the high-affinity CPA-bound state is similar to the closed configuration of the protopore gate of wild-type CLC-0. In the E166A mutant the glutamate side chain that occludes the permeation pathway is absent. Thus, if gating consists only in movement of this side-chain the mutant E166A should not be able to assume a closed conformation. It may thus be that fast gating in CLC-0 is more complex than anticipated from the bacterial structures.
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Weng, Xiaowei, Dimitry Chuprakov, Olga Kresse, Romain Prioul i Haotian Wang. "Hydraulic fracture-height containment by permeable weak bedding interfaces". GEOPHYSICS 83, nr 3 (1.05.2018): MR137—MR152. http://dx.doi.org/10.1190/geo2017-0048.1.
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In laminated formations, the vertical height growth of a hydraulic fracture can be strongly influenced by the interaction of the fracture tip with the bedding interfaces it crosses. A weak interface may fail in shear and then slip, depending on the strength and frictional properties, the effective vertical stress at the interface, and the net pressure. Shear failure and slippage at the interface can retard the height growth or even stop it completely. A 2D analytical model called the FracT model has been developed that examines the shear slippage along the bedding interface adjacent to the fracture tip and the resulting blunting of the fracture tip at the interface, as well as the stress condition on the face opposite from the hydraulic fracture tip for possible fracture nucleation that leads to fracture crossing. The growth of the shear slippage along the interface with time is coupled with the fluid flow into the permeable interface. A parametric study has been carried out to investigate the key formation parameters that influence the crossing/arrest of the fracture at the bedding interface and the shear slippage and depth of fluid penetration into the interface. The study suggests that the interfacial coefficient of friction and the ratio of the vertical to minimum horizontal stress are two of the most influential parameters governing fracture arrest by a weak interface. For the fracture tip to be arrested at the interface, the vertical stress acting on the interface must be close to the minimum horizontal stress or the interfacial coefficient of friction must be very small. The FracT model has also been integrated into a pseudo-3D-based complex hydraulic fracture model. This quantitative mechanistic model that incorporates a bedding-plane slip-driven mechanism is a necessary step to understand and bridge the characterization (sonic) and monitoring (microseismic) observations.
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HAZEL, ANDREW L., i MATTHIAS HEIL. "Three-dimensional airway reopening: the steady propagation of a semi-infinite bubble into a buckled elastic tube". Journal of Fluid Mechanics 478 (10.03.2003): 47–70. http://dx.doi.org/10.1017/s0022112002003452.
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We consider the steady propagation of an air finger into a buckled elastic tube initially filled with viscous fluid. This study is motivated by the physiological problem of pulmonary airway reopening. The system is modelled using geometrically nonlinear Kirchhoff–Love shell theory coupled to the free-surface Stokes equations. The resulting three-dimensional fluid–structure-interaction problem is solved numerically by a fully coupled finite element method.The system is governed by three dimensionless parameters: (i) the capillary number, Ca=μU/σ*, represents the ratio of viscous to surface-tension forces, where μ is the fluid viscosity, U is the finger's propagation speed and σ* is the surface tension at the air–liquid interface; (ii) σ=σ*/(RK) represents the ratio of surface tension to elastic forces, where R is the undeformed radius of the tube and K its bending modulus; and (iii) A∞=A*∞/(4R2), characterizes the initial degree of tube collapse, where A*∞ is the cross-sectional area of the tube far ahead of the bubble.The generic behaviour of the system is found to be very similar to that observed in previous two-dimensional models (Gaver et al. 1996; Heil 2000). In particular, we find a two-branch behaviour in the relationship between dimensionless propagation speed, Ca, and dimensionless bubble pressure, p*b/(σ*/R). At low Ca, a decrease in p*b is required to increase the propagation speed. We present a simple model that explains this behaviour and why it occurs in both two and three dimensions. At high Ca, p*b increases monotonically with propagation speed and p*b/(σ*/R) ∝ Ca for sufficiently large values of σ and Ca. In a frame of reference moving with the finger velocity, an open vortex develops ahead of the bubble tip at low Ca, but as Ca increases, the flow topology changes and the vortex disappears.An increase in dimensional surface tension, σ*, causes an increase in the bubble pressure required to drive the air finger at a given speed; p*b also increases with A*∞ and higher bubble pressures are required to open less strongly buckled tubes. This unexpected finding could have important physiological ramifications. If σ* is sufficiently small, steady airway reopening can occur when the bubble pressure is lower than the external (pleural) pressure, in which case the airway remains buckled (non-axisymmetric) after the passage of the air finger. Furthermore, we find that the maximum wall shear stresses exerted on the airways during reopening may be large enough to damage the lung tissue.
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Shakurova, Liia A., i Elena V. Kustova. "Boundary conditions for fluid-dynamic parameters of a single-component gas flow with vibrational deactivation on a solid wall". Vestnik of Saint Petersburg University. Mathematics. Mechanics. Astronomy 9, nr 2 (2022): 366–77. http://dx.doi.org/10.21638/spbu01.2022.216.
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Boundary conditions for fluid-dynamic parameters of a strongly non-equilibrium singlecomponent rarefied gas flow in the slip regime are obtained using kinetic-theory methods. The gas flow is described in the frame of the state-to-state approach assuming vibrational energy exchange as the slow relaxation process. The set of governing equations including conservation equations coupled with additional relaxation equations for vibrational state populations is presented. The gas-solid surface interaction is considered on the basis of the specular-diffusive model, and possible vibrational deactivation/excitation processes on the wall are taken into account. The obtained boundary conditions depend on the accommodation and deactivation coefficients along with the transport coefficients such as the multi-component vibrational energy diffusion and thermal diffusion coefficients; the thermal conductivity; the bulk and shear viscosity coefficients and the relaxation pressure. The dependence of boundary conditions on the normal mean stress has been obtained for the first time. In the particular case of the gas without internal degrees of freedom, the slip velocity and the temperature jump can be reduced to the well-known in the literature expressions. Implementation of the state-specific boundary conditions should not cause additional computational costs in numerical simulations of viscous flows in the state-to-state approach, since the slip/jump equations depend on the transport coefficients which have to be evaluated regardless of the boundary conditions used in the code.
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Habchi, Charbel, Serge Russeil, Daniel Bougeard, Jean-Luc Harion, Thierry Lemenand, Akram Ghanem, Dominique Della Valle i Hassan Peerhossaini. "Partitioned solver for strongly coupled fluid–structure interaction". Computers & Fluids 71 (styczeń 2013): 306–19. http://dx.doi.org/10.1016/j.compfluid.2012.11.004.
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Wagner, T., i N. J. Cook. "Late-orogenic alpine-type (apatite)-quartz fissure vein mineralization in the Rheinisches Schiefergebirge, NW Germany: mineralogy, formation conditions and lateral-secretionary origin". Mineralogical Magazine 64, nr 3 (czerwiec 2000): 539–60. http://dx.doi.org/10.1180/002646100549418.
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AbstractMineralogical, geochemical and fluid inclusion investigations of a representative suite of fissure vein mineralizations in the Rheinisches Schiefergebirge, NW Germany indicate a link to the latest stage of the Variscan orogenic evolution. Model P-T-conditions during initiation of fibrous fissure vein quartz growth are in the range 370–420°C at 0.2–0.7 kbar. The dataset suggests significant fluid cooling during evolution of the vein systems. Minimum temperatures at the end of fibrous quartz growth lie in the range 140–190°C, with conductive heat transfer and heat consumption during interaction with wallrock believed to be the main mechanisms responsible. Wallrock alteration is characterized by leaching and mobilization of most of the dominant vein components (quartz, albite, apatite), notably Si, Na and P. The principal stage of vein formation is, on the basis of available data, believed to relate to a process of intra-formational redistribution or lateral secretion. However, part of those elements deposited both in wallrock and fissure veins were probably supplied directly by the external fluid. Rates of fissure opening and material deposition were in equilibrium during the principal growth stage of fibrous quartz. However, this situation evolved due to a slowing down of material supply and deposition coupled with an increased rate of fissure opening to produce open fissures and formation of idiomorphic quartz crystals within them. Deposition depths were in the range of 0.6–2.1 km, appreciably lower than estimations of overburden. We believe therefore that formation of the fissure vein systems took place along the retrograde late–orogenic exhumation path, in a transitional stage between Variscan collision and a late- to post-orogenic extensional regime. Fluid composition characteristics also strongly suggest a relationship to the latest stages of the Variscan mineralization cycle in which low–salinity brines dominate. Development of fissure vein systems during the latest stages of continental collision, identified here from the Variscan orogeny, can be considered analogous with similar phenomena in the Alpine orogenic belt.
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Valencia, Juan D., Juan M. Mejía, Matteo Icardi i Richard Zabala. "Mathematical Modeling and Pilot Test Validation of Nanoparticles Injection in Heavy Hydrocarbon Reservoirs". Fluids 7, nr 4 (12.04.2022): 135. http://dx.doi.org/10.3390/fluids7040135.
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Heavy-oil mobility in reservoir rocks can be improved, using nanotechnology, by reducing the viscosity of the oil and improving the rock wettability to a water-wet condition. Previous pilot studies in Colombian heavy oil fields reported that nanoparticles dispersed in an oleic carrier fluid (diesel) increased oil production rates between 120–150% higher than before the interventions. However, to optimally deploy a massive nanofluid intervention campaign in heavy oil fields, it is valuable to implement simulation tools that can help to understand the role of operational parameters, to design the operations and to monitor the performance. The simulator must account for nanoparticle transport, transfer, and retention dynamics, as well as their impact on viscosity reduction and wettability restoration. In this paper, we developed and solved, numerically, a 3D mathematical model describing the multiphase flow and interaction of the nanoparticles with oil, brine, and rock surface, leading to viscosity reduction and wettability restoration. The model is based on a multiphase pseudo-compositional formulation, coupled with mass balance equations, of nanoparticles dispersed in water, nanoparticles dispersed in oil, and nanoparticles retained on the rock surface. We simulated a pilot test study of a nanofluid stimulation done in a Colombian heavy oil field. The injection, soaking, and production stages were simulated using a 3D single-well formulation of the mathematical model. The comparison of simulation results with the pilot test results shows that the model reproduced the field observations before and after the stimulation. Simulations showed that viscosity reduction during the post-stimulation period is strongly related to the detachment rate of nanoparticles. Simulation indicates that the recovery mechanism of the nanofluid stimulation is initially governed by viscosity reduction and wettability alteration. At latter times, wettability alteration is the main recovery mechanism. The nanoparticles transferred to the residual water promote the wettability alteration to a water wet condition. The model can be used to design field deployments of nanofluid interventions in heavy oil reservoirs.
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Beston, N. B. "RESERVOIR GEOLOGICAL MODELLING OF THE NORTH RANKIN FIELD, NORTHWEST AUSTRALIA". APPEA Journal 26, nr 1 (1986): 375. http://dx.doi.org/10.1071/aj85032.
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The North Rankin Field off northwestern Australia provides the major part of the gas reserves for the North West Shelf Project, one of the largest and most ambitious natural resource developments yet undertaken in Australia. Detailed reservoir geological modelling coupled with a three dimensional reservoir simulator have strongly enhanced development planning of the field.The North Rankin structure is a large horst feature of Upper Triassic to Lower Jurassic fluvial and marginal marine sediments unconformably overlain by Cretaceous claystones and marls. The sequence is comprised of braided stream 'sheet like' sandstones, fluvial meandering stream and floodplain sediments, and mixed marginal marine and fluvial channel sandstones.Comprehensive reservoir geological studies involving the examination of reservoir quality, distribution, and continuity were undertaken and combined with an extensive three dimensional seismic survey to provide improved structural definition. The resultant reservoir geological model, which required close interaction and integration of all petroleum engineering disciplines, provided not only the geological basis for improving the estimate of field reserves but also formed the geological input for a reservoir simulation model to optimise the development planning of the North Rankin Field and to predict the reservoir performance of this internally faulted field.The completion of the Domestic Gas Phase of the Project, which involved the drilling of seven development wells, has confirmed the reservoir geological/structural model thus providing a firm basis for the future development planning of the gas recycling and liquefied natural gas phases of the North West Shelf Project.
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Ibrahim, M. Y., C. Cook i K. Tieu. "Dynamic behaviour of a SCARA robot with links subjected to different velocity trajectories". Robotica 6, nr 2 (kwiecień 1988): 115–21. http://dx.doi.org/10.1017/s0263574700003921.
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SUMMARYThe dynamics of a mechanical manipulator have the inherent characteristics of being highly non-linear and strongly coupled due to the interaction of the inertial, centripetal, coriolis and gravitational forces.These characteristics produce difficulties in predicting the dynamic behaviour of a given manipulator's structure. These interactive forces depend largely on the geometrical configuration and operational conditions of a manipulator. Therefore, it is essential to investigate the dynamics behaviour under different conditions in order to obtain an optimal design.This paper presents a study of the dynamics behaviour of a robot's arm with particular reference to the mechanical manipulator being designed by the AEAC. A computer software package has been developed to facilitate the investigation of the potential dynamics behaviour of a robot's arm and provides the designer with useful information for the real time control of high performance robots. This package also enables the designer to closely monitor the implications of his design.The software of this package is based on the Lagrangian model, taking advantage of the recursive formulation. A brief description of the types of velocity trajectories used in this study is also included in this paper.The software for the modelling was written in FORTRAN 77 in single precision and run on a UNIVAC operating system.
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Doulcet, Benjamin, Christophe Devals, Bernd Nennemann, Maxime Gauthier, François Guibault i Jean-Yves Trépanier. "Two-way strongly coupled fluid-structure interaction simulations with OpenFOAM". IOP Conference Series: Earth and Environmental Science 405 (19.12.2019): 012007. http://dx.doi.org/10.1088/1755-1315/405/1/012007.
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Sudhakar, Y., i Wolfgang A. Wall. "A strongly coupled partitioned approach for fluid-structure-fracture interaction". International Journal for Numerical Methods in Fluids 87, nr 2 (19.01.2018): 90–108. http://dx.doi.org/10.1002/fld.4483.
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Zhang, Xuehui, i Wout Broere. "Monitoring of Tidal Variation and Temperature Change-Induced Movements of an Immersed Tunnel Using Distributed Optical Fiber Sensors (DOFSs)". Structural Control and Health Monitoring 2023 (12.07.2023): 1–17. http://dx.doi.org/10.1155/2023/2419495.
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The short-term deformation behavior of immersed tunnels due to daily or monthly temperature changes and tidal variations is often not monitored but forms important input for a structural health assessment of the tunnel. In this study, distributed optical fiber sensors (DOFSs) are used to monitor the short-term (daily and monthly) deformation behavior of an immersed tunnel. Joint opening and the relative settlement differences between tunnel elements are monitored simultaneously at subhour intervals. Measurements show that the variation in the joint opening is strongly correlated with temperature change, and the joint gap has a tendency to open at low temperatures and to close at increasing temperatures. Simultaneously, the entire immersed section behaves more like a rigid body and moves upwards and downwards periodically due to tidal fluctuations in the river, with an observed vertical movement of slightly less than one millimeter. The tide also causes local tilting of tunnel segments, and this tilting behavior differs between winter and summer, which implies that the (seasonal) temperature-induced joint deformations affect the robustness of the tunnel to tidal loads. A soil-tunnel structure interaction analysis reveals that the cyclic vertical movement of the tunnel is driven by retardation of the tidal wave in deeper soil layers, which can be captured by a coupled flow model. This study provides new insights into the short-term deformation behavior of immersed tunnels.
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Matthies, Hermann G., i Jan Steindorf. "Partitioned but strongly coupled iteration schemes for nonlinear fluid–structure interaction". Computers & Structures 80, nr 27-30 (listopad 2002): 1991–99. http://dx.doi.org/10.1016/s0045-7949(02)00259-6.
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WASHIO, Takumi, i Toshiaki HISADA. "Flexible Preconditioning for Strongly Coupled Equations in Fluid-Structure Interaction Problems". Proceedings of The Computational Mechanics Conference 2003.16 (2003): 87–88. http://dx.doi.org/10.1299/jsmecmd.2003.16.87.
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