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Kathleen Schjodt - One of the best experts on this subject based on the ideXlab platform.
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st and ale vms methods for patient specific cardiovascular Fluid Mechanics modeling
Mathematical Models and Methods in Applied Sciences, 2014Co-Authors: Kenji Takizawa, Tayfun E Tezduyar, Yuri Bazilevs, C C Long, Alison L Marsden, Kathleen SchjodtAbstract: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 earlier computations, we show how these core and special techniques work.
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patient specific cardiovascular Fluid Mechanics analysis with the st and ale vms methods
5th International Conference on Computational Methods for Coupled Problems in Science and Engineering 2013, 2014Co-Authors: Kenji Takizawa, Tayfun E Tezduyar, Yuri Bazilevs, Alison L Marsden, Christopher Long, Kathleen SchjodtAbstract:This chapter provides an overview of how patient-specific cardiovascular Fluid Mechanics analysis, including Fluid–structure interaction (FSI), can be carried out with the space–time (ST) and Arbitrary Lagrangian–Eulerian (ALE) techniques developed by the first three authors’ research teams. 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 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 earlier computations, we show how the core and special techniques work.
Kenji Takizawa - One of the best experts on this subject based on the ideXlab platform.
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st and ale vms methods for patient specific cardiovascular Fluid Mechanics modeling
Mathematical Models and Methods in Applied Sciences, 2014Co-Authors: Kenji Takizawa, Tayfun E Tezduyar, Yuri Bazilevs, C C Long, Alison L Marsden, Kathleen SchjodtAbstract: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 earlier computations, we show how these core and special techniques work.
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patient specific cardiovascular Fluid Mechanics analysis with the st and ale vms methods
5th International Conference on Computational Methods for Coupled Problems in Science and Engineering 2013, 2014Co-Authors: Kenji Takizawa, Tayfun E Tezduyar, Yuri Bazilevs, Alison L Marsden, Christopher Long, Kathleen SchjodtAbstract:This chapter provides an overview of how patient-specific cardiovascular Fluid Mechanics analysis, including Fluid–structure interaction (FSI), can be carried out with the space–time (ST) and Arbitrary Lagrangian–Eulerian (ALE) techniques developed by the first three authors’ research teams. 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 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 earlier computations, we show how the core and special techniques work.
Yuho Sakatani - One of the best experts on this subject based on the ideXlab platform.
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relativistic viscoelastic Fluid Mechanics
International Journal of Modern Physics: Conference Series, 2013Co-Authors: Masafumi Fukuma, Yuho SakataniAbstract:We explain the relativistic theory of viscoelasticity which we have recently constructed on the basis of Onsager's linear nonequilibrium thermodynamics. This theory universally reduces to the standard relativistic Navier-Stokes Fluid Mechanics in the long time limit. Since effects of elasticity are taken into account, the dynamics at short time scales is modified from that given by the Navier-Stokes equations, so that acausal problems intrinsic to relativistic Navier-Stokes Fluids are significantly remedied. We then present conformal higher-order viscoelastic Fluid Mechanics with strain allowed to take arbitrarily large values. We particularly show that a conformal second-order Fluid with all possible parameters in the constitutive equations can be obtained without breaking the hypothesis of local thermodynamic equilibrium, if the conformal Fluid is defined as the long time limit of a conformal second-order viscoelastic system.
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relativistic viscoelastic Fluid Mechanics
Physical Review E, 2011Co-Authors: Masafumi Fukuma, Yuho SakataniAbstract:A detailed study is carried out for the relativistic theory of viscoelasticity which was recently constructed on the basis of Onsager's linear nonequilibrium thermodynamics. After rederiving the theory using a local argument with the entropy current, we show that this theory universally reduces to the standard relativistic Navier-Stokes Fluid Mechanics in the long time limit. Since effects of elasticity are taken into account, the dynamics at short time scales is modified from that given by the Navier-Stokes equations, so that acausal problems intrinsic to relativistic Navier-Stokes Fluids are significantly remedied. We in particular show that the wave equations for the propagation of disturbance around a hydrostatic equilibrium in Minkowski space-time become symmetric hyperbolic for some range of parameters, so that the model is free of acausality problems. This observation suggests that the relativistic viscoelastic model with such parameters can be regarded as a causal completion of relativistic Navier-Stokes Fluid Mechanics. By adjusting parameters to various values, this theory can treat a wide variety of materials including elastic materials, Maxwell materials, Kelvin-Voigt materials, and (a nonlinearly generalized version of) simplified Israel-Stewart Fluids, and thus we expect the theory to be the most universal description of single-component relativistic continuum materials. We alsomore » show that the presence of strains and the corresponding change in temperature are naturally unified through the Tolman law in a generally covariant description of continuum Mechanics.« less
Tayfun E Tezduyar - One of the best experts on this subject based on the ideXlab platform.
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st and ale vms methods for patient specific cardiovascular Fluid Mechanics modeling
Mathematical Models and Methods in Applied Sciences, 2014Co-Authors: Kenji Takizawa, Tayfun E Tezduyar, Yuri Bazilevs, C C Long, Alison L Marsden, Kathleen SchjodtAbstract: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 earlier computations, we show how these core and special techniques work.
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patient specific cardiovascular Fluid Mechanics analysis with the st and ale vms methods
5th International Conference on Computational Methods for Coupled Problems in Science and Engineering 2013, 2014Co-Authors: Kenji Takizawa, Tayfun E Tezduyar, Yuri Bazilevs, Alison L Marsden, Christopher Long, Kathleen SchjodtAbstract:This chapter provides an overview of how patient-specific cardiovascular Fluid Mechanics analysis, including Fluid–structure interaction (FSI), can be carried out with the space–time (ST) and Arbitrary Lagrangian–Eulerian (ALE) techniques developed by the first three authors’ research teams. 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 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 earlier computations, we show how the core and special techniques work.
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arterial Fluid Mechanics modeling with the stabilized space time Fluid structure interaction technique
International Journal for Numerical Methods in Fluids, 2008Co-Authors: Tayfun E Tezduyar, Sunil Sathe, Matthew Schwaab, Brian S ConklinAbstract:We present an overview of how the arterial Fluid Mechanics problems can be modeled with the stabilized space–time Fluid–structure interaction (SSTFSI) technique developed by the Team for Advanced Flow Simulation and Modeling (T★AFSM). The SSTFSI technique includes the enhancements introduced recently by the T★AFSM to increase the scope, accuracy, robustness and efficiency of this class of techniques. The SSTFSI technique is supplemented with a number of special techniques developed for arterial Fluid Mechanics modeling. These include a recipe for pre-FSI computations that improve the convergence of the FSI computations, using an estimated zero-pressure arterial geometry, and the sequentially coupled arterial FSI (SCAFSI) technique. The recipe for pre-FSI computations is based on the assumption that the arterial deformation during a cardiac cycle is driven mostly by the blood pressure. The SCAFSI technique, which was introduced as an approximate FSI approach in arterial Fluid Mechanics, is also based on that assumption. The need for an estimated zero-pressure arterial geometry is based on recognizing that the patient-specific image-based geometries correspond to time-averaged blood pressure values. In our arterial Fluid Mechanics modeling the arterial walls can be represented with the membrane or continuum elements, both of which are geometrically nonlinear, and the continuum element is made of hyperelastic (Fung) material. Test computations are presented for cerebral and abdominal aortic aneurysms, where the arterial geometries used in the computations are close approximations to the patient-specific image-based data. Copyright © 2007 John Wiley & Sons, Ltd.
Ajit P Yoganathan - One of the best experts on this subject based on the ideXlab platform.
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cardiovascular Fluid Mechanics laboratory
2009Co-Authors: Ajit P YoganathanAbstract:Ajit Yoganathan leads the Cardiovascular Fluid Mechanics Laboratory at Georgia Tech. It has been one of the pioneering laboratories in the world studying the function and Mechanics of heart valves and other complex cardiac defects.
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advances in cardiovascular Fluid Mechanics bench to bedside
Annals of the New York Academy of Sciences, 2009Co-Authors: Lakshmi Prasad Dasi, Philippe Sucosky, Diane De Zelicourt, Kartik S Sundareswaran, Jorge H Jimenez, Ajit P YoganathanAbstract:This paper presents recent advances in cardiovascular Fluid Mechanics that define the current state of the art. These studies include complex multimodal investigations with advanced measurement and simulation techniques. We first discuss the complex flows within the total cavopulmonary connection in Fontan patients. We emphasize the quantification of energy losses by studying the importance of caval offsets as well as the differences among various Fontan surgical protocols. In our studies of the Fluid Mechanics of prosthetic heart valves, we reveal for the first time the full three-dimensional complexity of flow fields in the vicinity of bileaflet and trileaflet valves and the microscopic hinge flow dynamics. We also present results of these valves functioning in a patient-specific native aorta geometry. Our in vitro mitral valve studies show the complex mechanism of the native mitral valve apparatus. We demonstrate that the different components of the mitral valve have independent and synergistically complex functions that allow the valve to operate efficiently. We also show how valve Mechanics change under pathological and repair conditions associated with enlarged ventricles. Finally, our ex vivo studies on the interactions between the aortic valve and its surrounding hemodynamic environment are aimed at providing insights into normal valve function and valve pathology. We describe the development of organ- and tissue-culture systems and the biological response of the tissue subjected to their respective simulated mechanical environment. The studies noted above have enhanced our understanding of the complex Fluid Mechanics associated with the cardiovascular system and have led to new translational technologies.
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Fluid Mechanics of heart valves
Annual Review of Biomedical Engineering, 2004Co-Authors: Ajit P Yoganathan, Casey S JonesAbstract:▪ Abstract Valvular heart disease is a life-threatening disease that afflicts millions of people worldwide and leads to approximately 250,000 valve repairs and/or replacements each year. Malfunction of a native valve impairs its efficient Fluid mechanic/hemodynamic performance. Artificial heart valves have been used since 1960 to replace diseased native valves and have saved millions of lives. Unfortunately, despite four decades of use, these devices are less than ideal and lead to many complications. Many of these complications/problems are directly related to the Fluid Mechanics associated with the various mechanical and bioprosthetic valve designs. This review focuses on the state-of-the-art experimental and computational Fluid Mechanics of native and prosthetic heart valves in current clinical use. The Fluid dynamic performance characteristics of caged-ball, tilting-disc, bileaflet mechanical valves and porcine and pericardial stented and nonstented bioprostheic valves are reviewed. Other issues relat...
