In this article we discuss the application of a Lagrange multiplier based fictitious domain method for the simulation of the motion of two rigid flaps in an unsteady flow generated by pressure gradients. The distribut...
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In this article we discuss the application of a Lagrange multiplier based fictitious domain method for the simulation of the motion of two rigid flaps in an unsteady flow generated by pressure gradients. The distributed Lagrange multiplier technique can be an important numerical tool to design a mechanical heart valve and investigate the flow around rigid flaps without assuming the motion of the flaps in advance. Here, we derive a mathematical formulation of a fluid-structure interaction model that includes the generalized Neumann boundary conditions on the upstream and downstream boundaries along with rigid flaps rotating around the fixed points. The solution method includes the finite element approximation for space and the Marchuk-Yanenko operator splitting scheme for time discretization. This study presents the numerical results obtained for flap motion for a simple sinusoidal wave. Furthermore, these simulations are extended to apply to a more complex biological system involving the systolic phase of the pulse pressure. (c) 2007 Elsevier Ltd. All rights reserved.
fluid-structure interaction (FSI) simulations of a cerebral aneurysm with the linearly elastic and hyper-elastic wall constitutive models are carried out to investigate the influence of the wall-structure model on pat...
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fluid-structure interaction (FSI) simulations of a cerebral aneurysm with the linearly elastic and hyper-elastic wall constitutive models are carried out to investigate the influence of the wall-structure model on patient-specific FSI simulations. The maximum displacement computed with the hyper-elastic model is 36% smaller compared to the linearly elastic material model, but the displacement patterns such as the site of local maxima are not sensitive to the wall models. The blood near the apex of an aneurysm is likely to be stagnant, which causes very low wall shear stress and is a factor in rupture by degrading the aneurysmal wall. In this study, however, relatively high flow velocities due to the interaction between the blood flow and aneurysmal wall are seen to be independent of the wall model. The present results indicate that both linearly elastic and hyper-elastic models can be useful to investigate aneurysm FSI.
Electrostatic micro-devices are simple but important for MEMS applications. Precise dynamic descriptions of these devices are often hard to obtain due to the electrostatic nonlinearity and the fluid-structure interact...
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ISBN:
(纸本)9783037857397
Electrostatic micro-devices are simple but important for MEMS applications. Precise dynamic descriptions of these devices are often hard to obtain due to the electrostatic nonlinearity and the fluid-structure interactions in devices. Here we present a comprehensive electrostatic-mechanical- fluidic coupling transient analysis for the pull-in process of two ends fixed micro-plate device. The numerical results are compared with the published experiment works of other researchers available in the literature, and thus the model had been validated. After that the proper orthogonal decomposition approach is performed for the snapshot matrixes which are sampled from an ensemble of the fully finite element results. The resulted spatial distribution modes of pressure show a higher spatial frequency toward the middle of the micro-plate, which indicates that the pressures at the moving edges of the plate are not equal to ambient pressure. Due to the increasing demands for simulation accuracy, the electrostatic-mechanical interactions and the nonlinear features of viscous loss from the surrounding fluid have to be taken into account in details.
There is an increasing interest in the marine industry to use composites to improve the hydrodynamic and structural performance of naval structures. Composite materials have high strength-to-weight and stiffness-to-we...
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There is an increasing interest in the marine industry to use composites to improve the hydrodynamic and structural performance of naval structures. Composite materials have high strength-to-weight and stiffness-to-weight ratios, and the fiber orientations can be exploited to tailor the structural deformation to reduce the load and stress variations by automatically adjusting the shape of the structure. For marine propellers, the bending-twisting coupling characteristics of anisotropic composites can be exploited to passively tailor the blade rake, skew, and pitch distributions to improve propeller performance. To fully explore the advantages of composite marine propellers, a coupled boundary element (BEM) and finite element (FEM) approach is presented to study the fluid-structure interaction of flexible composite propellers in subcavitating and cavitating flows. An overview of the formulation for both the fluid and structural models is presented. Experimental validation studies are shown for two composite propellers tested at the Naval Surface Warfare Center (NSWCCD). The feasibility of passive hydroelastic tailoring of composite marine propellers is discussed. Published by Elsevier Ltd.
The patients with aortic aneurysm, especially aortic arch aneurysm, are prone to have aortic dissection. For investigation of the effect of aneurysm and wall stiffness on wall stress distribution, both the nonaneurysm...
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The patients with aortic aneurysm, especially aortic arch aneurysm, are prone to have aortic dissection. For investigation of the effect of aneurysm and wall stiffness on wall stress distribution, both the nonaneurysm arch model and the aneurysm arch model are constructed. The fluidstructureinteraction in the arch model of aorta was implemented. The results show the stresses are much higher at inflection points in aneurysm model than in nonaneurysm model. and the stresses at media in stiffened wall are higher than in unstiffened wall. The high composite stress is located at inflection points and is much higher in aneurysm model. The arch aneurysm and wall stiffening are important determinants of peak wall stress in aortic wall.
fluid-structure interaction of panel in supersonic fluid passage is studied with subcycling and spline interpolation based predict-correct scheme. The passage is formed with two parallel panels, one is rigid and the o...
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fluid-structure interaction of panel in supersonic fluid passage is studied with subcycling and spline interpolation based predict-correct scheme. The passage is formed with two parallel panels, one is rigid and the other is flexible. The interaction between fluid flows and flexible panel is numerically studied, mainly focused on the effect of dynamic pressure and distance between two parallel panels. Subcycling and spline interpolation based predict-correct scheme is utilized to combine the vibration and fluid analysis and to stabilize long-term calculations to get accurate results. It’s demonstrated that the flutter characteristic of flexible panel is more complex with the increase of dynamic pressure and the decrease of distance between two parallel panels. Via analyzing the propagation and reflection of disturbance in passage, it’s determined as a main cause of the variations.
This paper presents two domain decomposition techniques for fixed grid fluid-structure interaction simulations that can be applied to the interaction of general structures with incompressible flows. One approach is ba...
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This paper presents two domain decomposition techniques for fixed grid fluid-structure interaction simulations that can be applied to the interaction of general structures with incompressible flows. One approach is based on an overlapping domain decomposition idea while the other uses non-overlapping domains. The first technique combines a fixed grid Chimera approach with arbitrary Lagrangean Eulerian based methods, the second one is based on an eXtended Finite Element Method (XFEM) strategy. Both techniques are used in a partitioned and strong coupling fluid-structure framework. The usage of such fixed-grid methods considerably increases the range of possible applications. Several test examples demonstrate key features of both methods.
In this study, we explore the possibility of energy harvesting from fluid flow through a turbine hosting ionic polymer metal composites (IPMCs). Specifically, IPMC harvesters are embedded in the blades of a small-scal...
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In this study, we explore the possibility of energy harvesting from fluid flow through a turbine hosting ionic polymer metal composites (IPMCs). Specifically, IPMC harvesters are embedded in the blades of a small-scale vertical axis water turbine to convert flow kinetics into electrical power via low-frequency flow-induced IPMC deformations. An in-house fabricated Savonius-Darrieus hybrid active turbine with three IPMCs is tested in a laboratory water tunnel to estimate the energy harvesting capabilities of the device as a function of the shunting electrical load. The turbine is shown to harvest a few nanowatt from a mean flow of 0.43 m s(-1) for shunting resistances in the range 100-1000 Omega. To establish a first understanding of the energy harvesting device, we propose a quasi-static hydroelastic model for the bending of the IPMCs and we utilize a black-box model to study their electromechanical response.
The physical processes associated with the implosion of cylindrical tubes in a hydrostatic underwater environment were investigated using high-speed three-dimensional digital image correlation (3D DIC). This study emp...
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The physical processes associated with the implosion of cylindrical tubes in a hydrostatic underwater environment were investigated using high-speed three-dimensional digital image correlation (3D DIC). This study emphasizes visualization and understanding of the real-time deformation of the implodable volume and the associated fluid-structure interaction phenomena. Aluminium 6061-T6 cylindrical tubes were used as the implodable volumes. Dynamic tourmaline pressure transducers were placed at selected locations to capture the pressure history generated during each implosion event. A series of small-scale calibration experiments were first performed to establish the applicability of 3D DIC for measuring the deformation of submerged objects. The results of these experiments indicated that the effects of refraction due to water and the optical windows can be accounted for by evaluation of the camera's intrinsic and extrinsic parameters using a submerged calibration grid when the surface normal of the optical windows is collinear with the camera's optical axis. Each pressure history was synchronized with its respective high-speed DIC measurements. DIC results showed that the highest rate of increase in contact area correlates to the largest pressure spike during the implosion process. The results also indicated that, for a given diameter, longer implodable volumes generated higher pressure spikes.
This paper provides a review of the space-time (ST) and Arbitrary Lagrangian-Eulerian (ALE) techniques developed by the first three authors' research teams for patient-specific cardiovascular fluid mechanics model...
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This paper provides a review of the space-time (ST) and Arbitrary Lagrangian-Eulerian (ALE) techniques developed by the first three authors' research teams for patient-specific cardiovascular fluid mechanics modeling, including fluid-structure interaction (FSI). The core methods are the ALE-based variational multiscale (ALE-VMS) method, the Deforming-Spatial-Domain/Stabilized ST formulation, and the stabilized ST FSI technique. A good number of special techniques targeting cardiovascular fluid mechanics have been developed to be used with the core methods. These include: (i) arterial-surface extraction and boundary condition techniques, (ii) techniques for using variable arterial wall thickness, (iii) methods for calculating an estimated zero-pressure arterial geometry, (iv) techniques for prestressing of the blood vessel wall, (v) mesh generation techniques for building layers of refined fluid mechanics mesh near the arterial walls, (vi) a special mapping technique for specifying the velocity profile at an inflow boundary with non-circular shape, (vii) a scaling technique for specifying a more realistic volumetric flow rate, (viii) techniques for the projection of fluid-structure interface stresses, (ix) a recipe for pre-FSI computations that improve the convergence of the FSI computations, (x) the Sequentially-Coupled Arterial FSI technique and its multiscale versions, (xi) techniques for calculation of the wall shear stress (WSS) and oscillatory shear index (OSI), (xii) methods for stent modeling and mesh generation, (xiii) methods for calculation of the particle residence time, and (xiv) methods for an estimated element-based zero-stress state for the artery. Here we provide an overview of the special techniques for WSS and OSI calculations, stent modeling and mesh generation, and calculation of the residence time with application to pulsatile ventricular assist device (PVAD). We provide references for some of the other special techniques. With results from earl
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