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.
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.
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.
The development of an efficient partitioned FSI coupling scheme is reported in this paper, aimed to facilitate interaction between an open-source CSD software package and an in-house academic CFD code. The coupling pr...
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ISBN:
(纸本)9780791850510
The development of an efficient partitioned FSI coupling scheme is reported in this paper, aimed to facilitate interaction between an open-source CSD software package and an in-house academic CFD code. The coupling procedure is based on Radial Basis Functions (RBFs) interpolation for both information transfer and mesh deformation, entailing no dependence on connectivities, and hence making it applicable to different type or even intersecting grids. However, the method calls for increased computational resources in its initial formulation;to alleviate this deficiency, appropriate acceleration techniques have been incorporated, namely the Partition of Unity (PoU) approach and a surface-point reduction scheme. The PoU approach was adopted in case of data transfer, localizing the interpolation process and therefore reducing the size of the coupling matrix. An alternative approach was applied to improve the efficiency of the mesh deformation procedure, based on the agglomeration of the flow/structure interface nodes used for the RBFs interpolation method. For the demonstration of the proposed scheme a static aeroelastic simulation of a real bridge model, during its construction phase, was performed. The extracted results exhibit its potential to encounter effectively such complicated test cases, in a computationally efficient way.
fluid-structure interaction simulations are crucial for many engineering problems. For example, the blood flow around new heart valves or the deployment of airbags during a car crash are often modeled with fluid- stru...
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fluid-structure interaction simulations are crucial for many engineering problems. For example, the blood flow around new heart valves or the deployment of airbags during a car crash are often modeled with fluid- structureinteraction simulations. Also, to design safe parachutes, simula- tions are carried out to model the unsteady deformations of the parachute during a jump. Thus, there is an apparent need for multi-physics software codes which can model fluid-structure interaction problems. However, current state-of-the-art solvers cannot be used for design or optimization studies of for example aircraft structures due to long simula- tion times. This is mainly caused by a large number of coupling iterations needed to reach convergence within each time step for a strongly cou- pled fluid-structure interaction simulation. Also, a large number of time steps are required to reach an acceptable accuracy in time for unsteady simulations. Hence, there is an urgency for efficiency improvements of fluid-structure interaction solvers. In this thesis, two approaches are investigated to decrease the computa- tional times for a fluid-structure interaction simulation: multi-level accel- eration of the coupled problem, and the use of higher order time integration schemes. Part I. Multi-level acceleration with manifold mapping for partitioned fluid-structure interaction Highly sophisticated software codes are available for each single physical phenomenon. It is desirable to reuse these codes for multi-physics simula- tions such as a fluid-structure interaction problem where separate fluid and solid solvers need to be coupled. This partitioned approach is in contrast to the monolithic approach where all governing equations are implemented in a single software package and solved as a large system of equations. The focus of the first part of this thesis is to accelerate the convergence of strongly coupled fluid-structure interaction problems, where the fluid solver and the structure
The crashworthiness of helicopter fuel tank is vital to the survivability of the passengers and structures. In order to understand and improve the crashworthiness of the soft fuel tank of helicopter during the crash, ...
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The crashworthiness of helicopter fuel tank is vital to the survivability of the passengers and structures. In order to understand and improve the crashworthiness of the soft fuel tank of helicopter during the crash, this paper investigated the dynamic behavior of the nylon woven fabric composite fuel tank striking on the ground. A fluid-structure interaction finite element model of the fuel tank based on the arbitrary Lagrangian-Eulerian method was constructed to elucidate the dynamic failure behavior. The drop impact tests were conducted to validate the accuracy of the numerical simulation. Good agreement was achieved between the experimental and numerical results of the impact force with the ground. The influences of the impact velocity, the impact angle, the thickness of the fuel tank wall and the volume fraction of water on the dynamic responses of the dropped fuel tank were studied. The results indicated that the corner of the fuel tank is the most vulnerable location during the impact with ground.
Previous studies showed that the effect of fluid-structure interaction(FSI) was significant on polymer composite structures under dynamic loading. In this study, fluid coupling effect was examined on composite structu...
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Previous studies showed that the effect of fluid-structure interaction(FSI) was significant on polymer composite structures under dynamic loading. In this study, fluid coupling effect was examined on composite structures. In other words, fluid was filled between two parallel structures. As one structure is subjected to dynamic loading, the motion of the other structure was examined. The cellular automata techniques were used for this study, and a series of parametric studies were conducted to understand what parameters were important to affect the fluid coupling.
In order to simulate and analyze the dynamic characteristics of the parachute from advanced tactical parachute system(ATPS),a nonlinear finite element algorithm and a preconditioning finite volume method are employed ...
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In order to simulate and analyze the dynamic characteristics of the parachute from advanced tactical parachute system(ATPS),a nonlinear finite element algorithm and a preconditioning finite volume method are employed and developed to construct three dimensional parachute fluid-structure interaction(FSI)*** fabric material is represented by membrane-cable elements,and geometrical nonlinear algorithm is employed with wrinkling technique embedded to simulate the large deformations of parachute structure by applying the NewtonRaphson iteration *** the other hand,the time-dependent flow surrounding parachute canopy is simulated using preconditioned lower-upper symmetric Gauss-Seidel(LU-SGS)*** pseudo solid dynamic mesh algorithm is employed to update the flow-field mesh based on the complex and arbitrary motion of parachute *** to the large amount of computation during the FSI simulation,massage passing interface(MPI)parallel computation technique is used for all those three modules to improve the performance of the FSI *** FSI method is tested to simulate one kind of ATPS parachutes to predict the parachute configuration and anticipate the parachute descent *** comparison of results between the proposed method and those in literatures demonstrates the method to be a useful tool for parachute designers.
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