ST and ALE-VMS methods for patient-specific cardiovascular fluid mechanics modeling

Abstract

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 patientspecific 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 2437 Math. Models Methods Appl. Sci. 2014.24:2437-2486. Downloaded from www.worldscientific.com by UNIVERSITY OF GEORGIA on 11/27/14. For personal use only. 2438 K. Takizawa et al.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 noncircular 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.

Free-surface flow modeling and simulation of horizontal-axis tidal-stream turbines

“…The level-set method [3-5, 48, 60, 61] is adopted to track the evolution of the free surface, which is treated as an air-water interface. The aerodynamics and hydrodynamics are governed by the Navier-Stokes equations of incompressible, two-fluid flows, in which the fluid density and A C C E P T E D M A N U S C R I P T [21,30,31,33,[66][67][68] formulation enhanced with weakly enforced of essential boundary conditions [15,22,28] is employed to discretize the free-surface flow equations. The sliding-interface formulation [23] is employed to account for the presence of tower and nacelle, thus enabling the so-called "full machine" simulation [43].…”

Computation of the Flow Over a Sphere at Re = 3700: A Comparison of Uniform and Turbulent Inflow Conditions

“…[17] and successfully employed in a number of fluid mechanics and fluid-structure interaction simulations in Refs. [16] and [18][19][20][21][22][23][24][25][26][27][28][29]. RBVMS performs well on laminar and turbulent flows, and dis crete solutions converge rapidly to DNS while yielding LES-like solutions on intermediate meshes.…”

Space–time computations in practical engineering applications: a summary of the 25-year history

“…The computations reported in 2014 were for bioinspired flapping-wing aerodynamics [101][102][103], patient-specific aneurysms blocked with stent [104], spacecraft parachute FSI [102,105], wind-turbine rotor aerodynamics and rotor and tower aerodynamics [102,103,106], FSI of cerebral arteries with aneurysm [102], and heart valve flow analysis [17]. The spacecraft parachute FSI analyses included clusters of parachutes with the original design and with modified geometry porosity, different designs of the suspension lines, disreefing of a single parachute from Stage 1 to 2 to 3, disreefing of a 2-parachute cluster from Stage 2 to 3, and a drogue parachute at Stage 1, 2 and 3 under different flight conditions.…”