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Turbulent flow in converging nozzles,part one:boundary layer solution

Applied Mathematics and Mechanics(English Edition) 2011年第5期32卷 645-662页

作者： R.MADDAHIAN b.FARHANIEH b.firoozabadi Center of Excellence in Energy Conversion School of Mechanical Engineering Sharif University of Technology

The boundary layer integral method is used to investigate the development of the turbulent swirling flow at the entrance region of a conical nozzle. The governing equations in the spherical coordinate system are simplified with the boundary layer as- sumptions and integrated through the boundary layer. The resulting sets of differential equations are then solved by the fourth-order Adams predictor-corrector method. The free vortex and uniform velocity profiles are applied for the tangential and axial velocities at the inlet region, respectively. Due to the lack of experimental data for swirling flows in converging nozzles, the developed model is validated against the numerical simulations. The results of numerical simulations demonstrate the capability of the analytical model in predicting boundary layer parameters such as the boundary layer growth, the shear rate, the boundary layer thickness, and the swirl intensity decay rate for different cone angles. The proposed method introduces a simple and robust procedure to investigate the boundary layer parameters inside the converging geometries.

关键词： swirling flow converging nozzle swirl intensity decay rate boundary layer integral method analytical solution

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Multidimensional modeling of the stenosed carotid artery: A novel CAD approach accompanied by an extensive lumped model

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Acta Mechanica Sinica 2014年第2期30卷 259-273页

作者： A.Kashefi M.Mahdinia b.firoozabadi M.Amirkhosravi G.Ahmadi M.S.Saidi Department of Mechanical Engineering Sharif University of Technology Department of Mechanical Engineering University of California Berkeley Faculty of Engineering Department of Mechanical EngineeringSharif University of Technology Faculty of Engineering Department of Mechanical and Aeronautical EngineeringClarkson University

This study describes a multidimensional 3D/lumped parameter（LP） model which contains appropriate inflow/outflow boundary conditions in order to model the entire human arterial trees. A new extensive LP model of the entire arterial network（48 arteries） was developed including the effect of vessel diameter tapering and the parameterization of resistance, conductor and inductor variables. A computer aided-design（CAD） algorithm was proposed to effciently handle the coupling of two or more 3D models with the LP model, and substantially lessen the coupling processing time. Realistic boundary conditions and Navier-Stokes equations in healthy and stenosed models of carotid artery bifurcation（CAb） were used to investigate the unsteady Newtonian blood flow velocity distribution in the internal carotid artery（ICA）. The present simulation results agree well with previous experimental and numerical studies. The outcomes of a pure LP model and those of the coupled 3D healthy model were found to be nearly the same in both cases. Concerning the various analyzed 3D zones, the stenosis growth in the ICA was not found as a crucial factor in determining the absorbing boundary *** paper demonstrates the advantages of coupling local and systemic models to comprehend physiological diseases of the cardiovascular system.

关键词： Hemodynamic 3D/LP coupling CAD Realis-tic boundary conditions Carotid artery bifurcation Stenosis

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