Xueying Huang^*, Chun Yang^†, Chun Yuan^‡, Fei Liu^‡, Gador Canton^‡, Jie Zheng^§, Pamela K. Woodard^§, Gregorio A. Sicard^¶, Dalin Tang^||

Molecular & Cellular Biomechanics, Vol.6, No.2, pp. 121-134, 2009, DOI:10.3970/mcb.2009.006.121

Abstract Image-based computational models for atherosclerotic plaques have been developed to perform mechanical analysis to quantify critical flow and stress/strain conditions related to plaque rupture which often leads directly to heart attack or stroke. An important modeling issue is how to determine zero stress state from in vivo plaque geometries. This paper presents a method to quantify human carotid artery axial and inner circumferential shrinkages by using patient-specific ex vivo and in vivo MRI images. A shrink-stretch process based on patient-specific in vivo plaque morphology and shrinkage data was introduced to shrink the in vivo geometry first to find the zero-stress… More >

Sangho Kim^∗,†, Peng Kai Ong^*, Paul C. Johnson^‡

Molecular & Cellular Biomechanics, Vol.6, No.2, pp. 83-92, 2009, DOI:10.3970/mcb.2009.006.083

Abstract Recently, we reported that collision efficiency (fraction of total collisions that result in the formation of aggregates) between red blood cells was an important factor in the formation of aggregates in postcapillary venules. In the present study, we focus on how high molecular weight dextran influences the overall radial migration trend of red blood cells in the postcapillary venule along a longitudinal distance of 50 μm from the bifurcation which would in turn affect collision behavior of these cells. A radial migration index, which defines the extent of radial migration of individual cells relative to the… More >

F. Fleissner¹, T. Haag², M. Hanss², P. Eberhard¹

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.2, pp. 181-196, 2009, DOI:10.3970/cmes.2009.052.181

Abstract In alpine regions human settlements and infrastructure are at risk to be hit by landslides or other types of geological flows. This paper presents a new approach that can aid the design of protective constructions. An uncertainty analysis of the flow around a debris barrier is carried out using a chute flow laboratory model of the actual debris flow. A series of discrete element simulations thereby serves to compare and assess two different barrier designs. In this study, the transformation method of fuzzy arithmetic is used to investigate the influence of epistemically uncertain model parameters. More >

R. Avila¹, S. N. Atluri²

CMES-Computer Modeling in Engineering & Sciences, Vol.54, No.1, pp. 15-64, 2009, DOI:10.3970/cmes.2009.054.015

Abstract The Meshless Local Petrov Galerkin (MLPG) method is used to solve the non-steady two dimensional Navier-Stokes equations. Transient laminar flow field calculations have been carried out in domains wherein certain surfaces have: (i) a sliding motion, (ii) a harmonic motion, (iii) an undulatory movement, and (iv) a contraction-expansion movement. The weak form of the governing equations has been formulated in a Cartesian coordinate system and taking into account the primitive variables of the flow field. A fully implicit pressure correction approach, which requires at each time step an iterative process to solve in a sequential… More >

M. O. Doğan^1,2, H. Class², R. Helmig²

CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.3, pp. 207-234, 2009, DOI:10.3970/cmes.2009.053.207

Abstract Many flow problems in environmental, technical and biological systems are characterized by a distinct interaction between a flow region in porous-medium and a free-flow region in quasi-one-dimensional hollow structures. In this study, different model concepts, based on a dual-continuum strategy, for the simulation of coupled porous-media flow and (lower-dimensional) pipe flow are further developed and tested. The dual-continuum concept is extended for coupling multi-phase porous-media flow with lower-dimensional single-phase free flow. The complexity of the considered flow regimes is increased gradually. Examples are given for a coupled single-phase incompressible and compressible flow in both porous-media More >

H. Naj^1,2,3, G. Mompean^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.2, pp. 181-206, 2009, DOI:10.3970/cmes.2009.053.181

Abstract The aim of this work is to predict numerically the turbulent flow through a straight square duct using a nonlinear stress-strain model. The paper considers the application of the Craft et al.'s model [Craft, Launder, and Suga (1996)] to the case of turbulent incompressible flow in a straight square duct. In order to handle wall proximity effects, damping functions are introduced. Using a priori and a posteriori investigations, we show the performance of this model to predict such flows. The analysis of the flow anisotropy is made using the anisotropy-invariant map proposed by Lumley and More >

Bhaskar Kumar¹, Sanjay Mittal^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.2, pp. 95-122, 2009, DOI:10.3970/cmes.2009.053.095

Abstract The steady flow past a circular cylinder is investigated. Symmetry conditions are imposed along the centerline of the flow field. The variation of the structure of the recirculation zone with the Reynolds number is studied. The effect of the location of lateral boundary on the flow is analyzed and compared with results from earlier studies. The eddy length varies linearly with Re. Three kinds of solutions, based on eddy structure, are found for different location of the lateral boundary. Global linear stability analysis has been carried out in a translating frame to determine the convective… More >

Yi W. Wan¹, Huan J. Keh²

CMES-Computer Modeling in Engineering & Sciences, Vol.53, No.1, pp. 73-94, 2009, DOI:10.3970/cmes.2009.053.073

Abstract The problem of the rotation of a rigid particle of revolution about its axis in a viscous fluid is studied theoretically in the steady limit of low Reynolds number. The fluid is allowed to slip at the surface of the particle. A singularity method based on the principle of distribution of a set of spherical singularities along the axis of revolution within a prolate particle or on the fundamental plane within an oblate particle is used to find the general solution for the fluid velocity field that satisfies the boundary condition at infinity. The slip… More >

A.R. da Silva¹, A. Silveira-Neto^2,3, D.A. Rade^2,4, R.Francis⁴, E.A. Santos⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.3, pp. 285-304, 2009, DOI:10.3970/cmes.2009.050.285

Abstract In the context of computational fluid dynamics a numerical investigation of incompressible flow around fixed pairs of rigid circular cylinders was carried out. The two-dimensional filtered Navier-Stokes equations with the Smagorinsky sub-grid scale model were solved using a Cartesian non-uniform grid. The immersed Boundary Method with the Virtual Physical Model was used in order to model the presence of two circular cylinders embedded in the flow. The fractional time step method was used to couple pressure and velocity fields. The simulations were carried out for Reynolds number equal to 72,000 for pitch ratio equal to More >

Alfredo Nicolás¹, Blanca Bermúdez², Elsa Báez³

CMES-Computer Modeling in Engineering & Sciences, Vol.48, No.1, pp. 83-106, 2009, DOI:10.3970/cmes.2009.048.083

Abstract Numerical results of natural convection flows in two-dimensional cavities, filled with air, are presented to study the effects on the characteristics of the flows as some parameters vary: the Rayleigh number Ra and the aspect ratio A of the cavity. This kind of thermal flows may be modeled by the unsteady Boussinesq approximation in stream function-vorticity variables. The results are obtained with a simple numerical scheme, previously reported for isothermal/mixed convection flows, based mainly on a fixed point iterative process applied to the non-linear elliptic system that results after time discretization. The evolution of the flows,… More >