摘要:

The non-oscillatory central difference scheme of Nessyahu and Tadmor, in which the resolution or Riemann problems at the cell interfaces is by-passed thanks to the use of the staggered Lax-Friedrichs scheme, is extended here to a two-step, two-dimensional non-oscillatory centered scheme in finite volume formulation. The construction of the scheme rests on a finite volume extension of the Lax-Friedrichs scheme, in which the finite volume cells are the barycentric cells constructed around the nodes of an FEM triangulation, for odd time steps, and some quadrilateral cells associated with this triangulation, for even time steps.

ISSN:1061-8562    

DOI:10.1080/10618569808940837

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To validate the pathologoical flow condition as the etiology of site-specific athero sclerosis, computer simulation and analysis are presented. Two extreme pulsatile flows, as have been measured in human femoral arteries, are used to numerically simulate in-vivo blood flow. The pulse with a steep temporal velocity gradient is assigned as “steep” pulse whereas the one with a lesser slope is called “less-steep” pulse. The effect of the extreme two pulses on the injury of endothelial cells in a 90°femoral artery of human is investigated by calculating flow parameters including instantaneous wall shear stresses. At the proximal and the distal branch apex, the oscillating wall shear stresses calculated from the ‘steep’ pulse cycle are found to be substantially greater than those from the ‘less-steep’ one. In contrast, for a straight artery, insignificant changes in flow parameters are observed for the extreme two pulses. It is evident from the calculated local wall shear stress that pathological changes can occur in the intima cells of the branch arterial wall and less likely in the straight arterial wall. An alteration of the pulsatile flow condition from a ‘steep’ to a ‘less-steep’ pulse, as may be achieved by pharmaceutical, chemical, or mechanical means, may be one of the possible ways to reduce the risk, thus slow the progression of or cause regression of arterial diseases, such as heart attack and stroke.

ISSN:1061-8562    

DOI:10.1080/10618569808940838

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We develop a least-squares approach for a boundary control problem associated with the incompressible Navier-Stokes equations. Iterative methods are suggested for solution of the discrete nonlinear optimization problem. Results of some computational experiments concerning control of the driven cavity flow arc also presented. These experiments confirm, among other things, a hypothesis due to Desai and Ito, that one-dimensional boundary control may fail to achieve the control objectives for high values of the Reynolds number.

ISSN:1061-8562    

DOI:10.1080/10618569808940839

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A time and space accurate method for computing the movement of an adsorbing contaminant in a carrier fluid is presented. The method uses a finite element analog to a previously described finite difference approach which can accurately describe movement of highly convected, but dispersing fronts. An operator splitting scheme between convection and dispersion is employed which provides fourth order time accuracy on the convection step. The higher accuracy for the convection step is also accompanied with belter mass conservation properties than is common for most algorithms which model purely convective problems. The method is demonstrated on problems varying in one dimension by applications to pure convection-dispersion, the nonlinear Burger's equation, convection-reaction equations, and convection-dispersion through an adsorbing medium. The model predictions are found to provide accurate and stable results.

ISSN:1061-8562    

DOI:10.1080/10618569808940840

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Unsteady Newtonian fluid flow through stenosed vessels, with lumen of constriction in the range 0–75%, is numerically analyzed. A transient velocity-pressure (UVP) finite element method (FEM) in conjunction with a stable time integration scheme, which monitors the error at every time step and then automatically decides the next time step, is employed in the flow analysis. The influence of the degree of the stenosis on the velocity, pressure and stress fields are thoroughly studied. At all time t, the pressure gradient and the impedence across the stenosis, and the peak wall shear stress are found to be increasingly sensitive to increasing degree of the stenosis. Recirculation regions, varying with time and sensitive to stenosis height are noticed both proximal and distal to the stenosis. In the regions adjacent to the stenosis a spatial and temporal variation in the transverse velocities and the pressure normal to the central axis, owing to the nonlinear effects of the vessel geometry, are noticed.

ISSN:1061-8562    

DOI:10.1080/10618569808940841

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An estimation method for gravity water wave propagation combining the finite element method and the Kalman filtering technique is presented. The method is further simplified to reduce the computational effort. According to the results obtained with this method, it is possible to estimate the water surface profile by taking into account the measured data, and to filter out the noise included in the measured data and the finite element approximation.

ISSN:1061-8562    

DOI:10.1080/10618569808940842

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A numerical analysis of laminar flow through square-edged orifice has been studied for Reynolds number in the range 0 < Re0< 2000 with β values varying from 0.2 to 0.8 and withl* values varying from 1/16 to 1. It is shown thai the flow discharge coefficient gradually decreases when the orifice thickness/diameter ratio increases for a high porosity.

ISSN:1061-8562    

DOI:10.1080/10618569808940843

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor