fluid-structure interaction in viscoelastic vessels is often modelled with the motivation to understand arterial blood flow. Traveling waves in flexible vessels have been analyzed and experiments have been performed b...
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ISBN:
(纸本)9780791850404
fluid-structure interaction in viscoelastic vessels is often modelled with the motivation to understand arterial blood flow. Traveling waves in flexible vessels have been analyzed and experiments have been performed by many researchers. Theoretical models often focus either on the flow of the liquid (assuming that the wall is rigid), or on the displacement of the wall (assuming that the wall is elastic). Analytical theories on the interaction between the fluid and the wall are limited;models are typically based on numerical techniques. For assessing the validity of analytical and numerical models welldefined in-vitro experiments are of great importance. The objective of this paper is to present a transmission line analytical theory and validate it against experimental data obtained for aortic analogues. Transition line theory allows for including non-uniformities of vessels by capturing them as several uniform segments. The analytical theory is set up by multiple sections and a formulation is derived that incorporates the multiple reflections and transmissions of propagating waves through the interfaces of these sections. The pressure, flow and wall distention results obtained from the analytical model are compared with experimental data from a straight uniform tube and a tapered one with aortic relevance. The analytical results and the experimental measurements were found to be in good agreement for both the uniform and tapered tubes.
The efficient numerical simulation of fluid-structure interaction (FSI) problems is of growing interest in many engineering fields. Staggered approaches are particularly interesting because they allow for the reuse of...
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ISBN:
(纸本)9788494690921
The efficient numerical simulation of fluid-structure interaction (FSI) problems is of growing interest in many engineering fields. Staggered approaches are particularly interesting because they allow for the reuse of existing softwares. In this work we propose a staggered scheme based on the weakly compressible PFEM for the fluid domain and SIMULIA Abaqus/Explicit for the solid domain. The coupling is treated with a domain decomposition approach based on the Gravouil-Combescure algorithm. The main goal is to show the possibility of a fully explicit coupling with different time step size on the two phases (fluid and solid) and incompatible mesh at the interfaces. 2D test-cases will be presented to validate the proposed coupling technique. The explicit time integration scheme for both the fluid and solid subdomains, together with the explicit treatment of the coupling, makes this method appealing for applications in a variety of engineering problems with fast dynamics and/or a high degree of non-linearity.
Partitioned approaches for the solution of fluid-structure interaction (FSI) problems are particularly interesting because, among other aspects, they allow for the reuse of existing software. In this work, we propose ...
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ISBN:
(纸本)9788494690976
Partitioned approaches for the solution of fluid-structure interaction (FSI) problems are particularly interesting because, among other aspects, they allow for the reuse of existing software. In this work, we propose a partitioned scheme based on the weakly compressible PFEM for the fluid domain and SIMULIA Abaqus/Explicit for the solid domain. The coupling is treated with a domain decomposition approach based on the Gravouil-Combescure algorithm. This approach allows for the use of different time step size on the two phases (fluid and solid) and incompatible mesh at the interfaces. The main goal of the proposed fomrulation is to show the possibility of a strong fluid-structure interaction coupling within of fully explicit sframework. 2D test-cases will be presented to validate the proposed coupling technique. The explicit time integration scheme for both the fluid and solid subdomains, together with the explicit treatment of the coupling, makes this method appealing for large scale applications in a variety of engineering problems with fast dynamics and/or a high degree of non-linearity.
Numerical models of native heart valves are being used to study valve biomechanics to aid design and development of repair procedures and replacement devices. These models have evolved from simple two-dimensional appr...
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Numerical models of native heart valves are being used to study valve biomechanics to aid design and development of repair procedures and replacement devices. These models have evolved from simple two-dimensional approximations to complex three-dimensional, fully coupled fluid-structure interaction (FSI) systems. Such simulations are useful for predicting the mechanical and hemodynamic loading on implanted valve devices. A current challenge for improving the accuracy of these predictions is choosing and implementing modeling boundary conditions. In order to address this challenge, we are utilizing an advanced in vitro system to validate FSI conditions for the mitral valve system. Explanted ovine mitral valves were mounted in an in vitro setup, and structural data for the mitral valve was acquired with CT. Experimental data from the in vitro ovine mitral valve system were used to validate the computational model. As the valve closes, the hemodynamic data, high speed leaflet dynamics, and force vectors from the in vitro system were compared to the results of the FSI simulation computational model. The total force of 2.6 N per papillary muscle is matched by the computational model. In vitro and in vivo force measurements enable validating and adjusting material parameters to improve the accuracy of computational models. The simulations can then be used to answer questions that are otherwise not possible to investigate experimentally. This work is important to maximize the validity of computational models of not just the mitral valve, but any biomechanical aspect using computational simulation in designing medical devices.
An efficient and scalable numerical method for massively parallel computing of fluid-structure interaction systems has been developed for biomedical applications. To facilitate the treatment of complex geometry, a ful...
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An efficient and scalable numerical method for massively parallel computing of fluid-structure interaction systems has been developed for biomedical applications. To facilitate the treatment of complex geometry, a full Eulerian method is employed to couple the incompressible motions of fluid and hyperelastic materials. Instead of implicitly solving the pressure Poisson equation, a novel artificial compressibility method with adaptive parameters, which are determined to guarantee the computed field to be nearly incompressible, is proposed. In both weak and strong scaling tests, the developed solver attains excellent scalability on the K computer. A sustained performance of 4.54 Pflops (42.7% of peak) has been achieved for a microchannel flow involving more than 5 million deformable bodies using 6.96x10(11) grid points with 663,552 compute cores. We study arteriole blood flows in a brain to gain insight into dynamic interactions among motions of plasma and blood cells, which are relevant to initial thrombus formations. (C) 2017 Published by Elsevier B.V.
In this work, we focus on the effect of supporting structures on the loads acting on a large horizontal axis wind turbine. The transient fluid-structure interaction (FSI) is simulated by an in-house code which couples...
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ISBN:
(纸本)9788494690921
In this work, we focus on the effect of supporting structures on the loads acting on a large horizontal axis wind turbine. The transient fluid-structure interaction (FSI) is simulated by an in-house code which couples two solvers, one for the computational fluid dynamics (CFD) and one for the computational structure mechanics (CSM). Strong coupling is applied as the force and displacement equilibriums are always enforced on the fluidstructure interface. The flexibility of the three blades of the considered machine is taken into account. The accurate CSM model reproduces in details the composite layups, foam, adhesive and internal stiffeners of the blades. On the other hand, the supporting structures (tower and nacelle) are considered to be rigid. On the fluid side, a fully hexahedral mesh is generated by a multi-block strategy. The same mesh is continuously deformed and adapted according to the displacement of the fluid-structure interface. The atmospheric boundary layer (ABL) under neutral conditions is included and consistently preserved along the computational domain. Using the outlined model, the blade deflections with and without supporting structure are compared. The effects of this transient interaction are highlighted throughout the rotation of the rotor, in terms of both wind energy conversion performance of the machine and structural response of each component. The maximal stress in the blade material as a function of time is compared with and without the presence of the tower in the wake of the rotor. Only a few similar works are reported to appear in literature [1, 2], whereas none of them currently includes the ABL or show detailed information about the internal stresses in the composite blades.
Aortic valve diseases are among the most common cardiovascular defects. Since a non-functioning valve results in disturbed blood flow conditions, the diagnosis of such defects is based on identification of stenosis vi...
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Uniform stability to a non-trivial equilibrium of a nonlinear fluidstructureinteraction model is studied. To achieve this goal, control action depending on the equilibrium and applied to the fluid is proposed. The s...
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Uniform stability to a non-trivial equilibrium of a nonlinear fluidstructureinteraction model is studied. To achieve this goal, control action depending on the equilibrium and applied to the fluid is proposed. The stabilization result obtained is global and no assumptions on the smallness of the initial data or the size of equilibrium point are needed. Due to viscoelasticity, the boundary transmission conditions are highly unbounded, which requires perturbation independent argument. To overcome this difficulty, we seek to construct special multipliers based on the Stokes solver and the projection operator from to a special subspace expanded by the eigenfunction corresponding to the smallest eigenvalue of with zero Neumann boundary condition.
A fluid-structure interaction (FSI) tool that couples existing independent fluid and solid solvers into a single synchronization and communication framework based on the Python language is presented. Each solver has t...
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ISBN:
(纸本)9788494690921
A fluid-structure interaction (FSI) tool that couples existing independent fluid and solid solvers into a single synchronization and communication framework based on the Python language is presented. Each solver has to be wrapped in a Python layer in order to embed their functionalities (usually written in a compiled language) into a Python object, that is called and used by the coupler. Thus a staggered strong coupling can be achieved for time-dependent FSI problems such as aeroelastic flutter or vortex-induced vibrations (VIV). The synchronization between the solvers is performed with the block Gauss-Seidel algorithm and a dynamic under-relaxation. The tool allows non-matching meshes between the fluid and structure domains and it is optimised to work in parallel using Message Passive Interface (MPI). These capabilities are demonstrated on typical validation cases. The open-source code SU2 is used to compute the fluid region while the solid region is computed either by a simple rigid body integrator, by an in-house nonlinear Finite Element code (Metafor) or by the structural solver TACS. First, the accuracy of the results is demonstrated and then the modularity of the coupling as well as its ease of use is highlighted.
Up to 14% of the U.S. population is estimated to have obstructive sleep apnea (OSA), while the outcomes of the treatments have variable results. In the current study, a three-dimensional fluid-structure interaction mo...
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Up to 14% of the U.S. population is estimated to have obstructive sleep apnea (OSA), while the outcomes of the treatments have variable results. In the current study, a three-dimensional fluid-structure interaction modeling was applied to simulate the upper airway to identify the precise location, severity, and characteristic of airway collapse. This was accomplished using Simpleware and ANSYS (R) software applied to a 3-D rendering of the airway in a real patient with severe OSA. During this simulation, areas which are prone to collapse and precipitate apneic episodes were identified at the tip of the soft palate and the base of the tongue, with intrathoracic pressure as low as similar to 1370 Pa. These results are consistent with anatomical structures currently indicated and targeted in the treatment of OSA. This improved FSI modeling simulation, which is the first to completely model the whole upper airway without consideration of the nasal cavity in OSA, and can allow virtual modification of the airway prior to actual treatment by doctors.
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