Effect of a Lipid Pool on Stress/Strain Distributions in Stenotic Arteries: 3-D Fluid-Structure Interactions (FSI) Models

2004 ◽  
Vol 126 (3) ◽  
pp. 363-370 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Shunichi Kobayashi ◽  
David N. Ku
Keyword(s):  
Stokes Equations ◽  
Plaque Rupture ◽  
Strain Analysis ◽  
Fluid Structure Interactions ◽  
Stress Strain ◽  
Fluid Structure ◽  
Lipid Pool ◽  
Stenosis Severity ◽  
Stenotic Arteries

Nonlinear 3-D models with fluid-structure interactions (FSI) based on in vitro experiments are introduced and solved by ADINA to perform flow and stress/strain analysis for stenotic arteries with lipid cores. Navier-Stokes equations are used as the governing equations for the fluid. Hyperelastic Mooney-Rivlin models are used for both the arteries and lipid cores. Our results indicate that critical plaque stress/strain conditions are affected considerably by stenosis severity, eccentricity, lipid pool size, shape and position, plaque cap thickness, axial stretch, pressure, and fluid-structure interactions, and may be used for possible plaque rupture predictions.

Quantifying Effects of Controlling Factors on Flow and Stress Distribution in Stenotic Arteries With Lipid Cores

2003 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Shunichi Kobayashi ◽  
David N. Ku
Keyword(s):  
Material Properties ◽  
Stokes Equations ◽  
Nonlinear Models ◽  
Strain Analysis ◽  
Core Material ◽  
Stress Strain ◽  
Fluid Structure ◽  
Lipid Core ◽  
Stenosis Severity ◽  
Stenotic Arteries

2D and 3D multi-physics experiment-based nonlinear models with fluid-structure interactions (FSI) and structure-structure interactions (SSI) are introduced to model blood flow and stress/strain distributions in stenotic arteries with lipid pools. Material properties for the vessel and plaque are based on experimental measurements and information available in the literature (Huang et. al., 2001; Tang et. al., 2001). The Navier-Stokes equations are used as the governing equations for the fluid. Mooney-Rivlin models are used for both arteries and lipid cores. A well-tested finite element package ADINA is used to solve the models to perform flow and stress/strain analysis. Our results indicate that artery plaque stress/strain distributions are affected considerably (50%–400% or even more) by vessel material properties, stenosis severity and eccentricity, tube axial pre-stretch, pressure conditions, lipid core material property, size, position and geometry, and fluid-structure and structure-structure (vessel wall and lipid core) interactions. Differences in model assumptions and controlling factor specifications must be taken into consideration when interpreting the significance of computational results.

2D and 3D multi-physics models for flow and nonlinear stress/strain analysis of stenotic arteries with lipid cores

2003 ◽  
pp. 1829-1832 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Homer Walker ◽  
Shunichi Kobayashi ◽  
Jie Zheng ◽  
...  
Keyword(s):  
Strain Analysis ◽  
Stress Strain ◽  
Nonlinear Stress ◽  
Stenotic Arteries ◽  
2D And 3D

On the estimation of sound produced by complex fluid–structure interactions, with application to a vortex interacting with a shrouded rotor

1991 ◽  
Vol 433 (1889) ◽  
pp. 573-598 ◽  
Keyword(s):  
Numerical Solutions ◽  
Stokes Equations ◽  
Fluid Velocity ◽  
Leading Edge ◽  
Surface Forces ◽  
Fluid Structure Interactions ◽  
Fluid Structure ◽  
Frequency Sound ◽  
Complex Fluid ◽  
Shrouded Rotor

An approximate analytical method is described for determining the sound produced by a class of complex fluid-structure interactions in low Mach number flows. This can be used to model noise sources in practical systems, and to check the accuracy of predictions based on time accurate numerical solutions of the Navier-Stokes equations. The dominant acoustic sources are dipoles whose strengths are dependent on the unsteady surface forces, and are expressed in terms of fluid velocity and vorticity, and a set of harmonic functions determined by the shapes of the structural elements interacting with the flow. (The theory of surface forces for arbitrary motion of a rigid body in viscous, incompressible flow in the presence of a fixed system of boundaries is discussed in an appendix.) These elements can influence both the generation and propagation of sound, and are frequently sources of new vorticity shed into wakes. The procedure is illustrated by application to a model problem in which sound is generated by a vortex interacting with a shrouded rotor in a duct. High-frequency sound is generated when the vortex is draw n into the rotor disc and ‘chopped’ by the blades. Sound is also produced through indirect blade-vortex interactions which, in this case, occur as a result of unsteady blade loadings produced when the core of the vortex is close to the leading edge of the shroud. This is relatively low-frequency sound and is the only component of blade-vortex interaction noise when the vortex is convected through the gap between the shroud and wall of the duct.

scholarly journals A natural element updated Lagrangian approach for modelling fluid structure interactions

2007 ◽  
pp. 323-336
Author(s):  
Andrés Galavís ◽  
David González ◽  
Elias Cueto ◽  
Francisco Chinesta ◽  
Manuel Doblaré
Keyword(s):  
Stokes Equations ◽  
Theoretical Description ◽  
Navier Stokes ◽  
Fluid Structure Interactions ◽  
Navier Stokes Equations ◽  
Fluid Structure ◽  
Lagrangian Framework ◽  
Natural Element ◽  
Updated Lagrangian Approach ◽  
Updated Lagrangian

In this paper we present a novel methodology for the numerical simulation of fluid structure interactions in the presence of free surfaces. It is based on the use of the Natural Element Method (NEM) in an updated Lagrangian framework, together with the integration of the Navier-Stokes equations by employing a Galerkin-characteristics formulation. Tracking of the free-surface is made by employing shape constructors, in particular α- shapes. A theoretical description of the method is made and also some examples of the performance of the technique are included.

scholarly journals Parallel time-stepping for fluid-structure interactions

2021 ◽  
Author(s):  
Thomas Richter ◽  
Nils Margenberg
Keyword(s):  
Stokes Equations ◽  
Numerical Test ◽  
Time Integration ◽  
Navier Stokes ◽  
Fluid Structure Interactions ◽  
Fluid Structure ◽  
Solution Approach ◽  
Time Stepping ◽  
Parallel Time ◽  
Nicolson Scheme

We present a parallel time-stepping method for fluid-structure   interactions. The interaction between the incompressible   Navier-Stokes equations and a hyperelastic solid is formulated in a   fully monolithic framework. Discretization in space is based on   equal order finite element for all variables and a variant of the   Crank-Nicolson scheme is used as second order time integrator. To   accelerate the solution of the systems, we analyze a parallel-in   time method. For different numerical test cases in 2d and in 3d we   present the efficiency of the resulting solution approach. We also   discuss some challenges and limitations that are connected   to the special structure of fluid-structure interaction problem.   In particular, we will investigate stability and dissipation     effects of the time integration and their influence on the     convergence of the Parareal method. It turns out that especially     processes based on an internal dynamics (e.g. driven by the vortex     street around an elastic obstacle) cause great     difficulties. Configurations however, which are driven by     oscillatory problem data, are well-suited for parallel time     stepping and allow for substantial speedups.

Cyclic Bending of Coronary Plaques Leads to Much Higher Stress Variations: A Major Factor Contributing to Plaque Rupture Risk

2007 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Jie Zheng ◽  
Shunichi Kobayashi ◽  
Gregorio A. Sicard ◽  
...  
Keyword(s):  
Plaque Rupture ◽  
Strain Analysis ◽  
Atherosclerotic Plaques ◽  
Rupture Risk ◽  
Cyclic Bending ◽  
Clinical Events ◽  
Stenosis Severity ◽  
Atherosclerotic Plaque Rupture ◽  
Component Models ◽  
Stress Variations

Mechanical forces play an important role in the complicated process of atherosclerotic plaque rupture which often leads to serious clinical events such as stroke and heart attack [4]. Factors causing the vulnerable plaque cap to fracture are important clinically [2–7]. It is known that coronary plaques are more likely to rupture compared to carotid plaques under comparable conditions (such as stenosis severity at about 50% by diameter). One possible reason is that coronary arteries are under cyclic bending caused by heart motions and compressions. We hypothesize that cyclic bending of coronary atherosclerotic plaques may be a major contributor to critical stress variations in the plaque leading to increased plaque rupture risk. We have developed MRI-based 3D multi-component models with fluid-structure interactions (FSI) in order to perform flow and stress/strain analysis for atherosclerotic plaques and identify possible mechanical and morphological indices for accurate plaque vulnerability assessment [6–7].

Heart Composite Material Model for Stress-Strain Analysis

2003 ◽  
Author(s):  
Zhenhua Hu ◽  
Dimitris Metaxas ◽  
Leon Axel
Keyword(s):  
Fiber Orientation ◽  
Strain Energy ◽  
Strain Analysis ◽  
Material Model ◽  
Time Step ◽  
Stress Strain ◽  
Energy Functions ◽  
Strain Energy Functions

Mechanical properties of the myocardium have been investigated intensively in the past four decades. Due to the non-linearity and history dependence of myocardial deformation, many complex strain energy functions have been used to describe the stress-strain relationship in the myocardium. These functions are good at fitting in-vitro experimental data from myocardial stretch testing into strain energy functions. However, it is difficult to model in-vivo myocardium by using strain energy functions. In a previous paper [1], we have implemented a transversely anisotropic material model to estimate in-vivo strain and stress in the myocardium. In this work, the fiber orientation is updated at each time step from the end of diastole to the end of systole; the stiffness matrix is recalculated using the current fiber orientation. We also extend our model to include residual ventricular stresses and time-dependent blood pressure in the ventricular cavities.

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