M. R. Modarres- Razavi, H. Niazmand and S. A. Mirbozorgi,
Volume 20, Issue 2 (4-2001)
Abstract
In this paper, the flow-field of an incompressible viscous flow past a solid-sphere at low Reynolds numbers (up to 270) is investigated numerically. In order to extend the capabilities of the finite volume method, the boundary (body) fitted coordinates (BFC) method is used. Transformation of the partial differential equations to algebraic relations is based on the finite-volume method with collocated variables arrangement. For solving the obtained algebraic relations, the TDMA in periodic state is used. To approximate the convective fluxes, the differencing scheme of Van leer is used and SIMPLEC handles the linkage between velocities and pressures. The verification of the code is checked by the analysis of flow past a solid sphere at low Reynolds numbers of 20 to 210. A good agreement is obtained between the present results and the available experimental and numerical data. The flow-field past a sphere at low Reynolds numbers of 210 to 270 shows that the steady non-axisymmetric regime is going to build up at the Reynolds number of 211.
Keywords: Solid-Sphere, Wake, Three Dimensional Analysis, Boundary Fitted Cordinates
E. Ebrahimnia-Bajestan, H. Niazmand,
Volume 36, Issue 1 (9-2017)
Abstract
In this paper, numerical simulation of flow and heat transfer of Al2O3/water nanofluid has been carried out through three different geometries involving a straight pipe, a 90o curved pipe and a 180o curved pipe under constant heat flux condition. Employing singe-phase model for the nanofluid, the Navier-Stokes and energy equations for an incompressible and laminar flow have been solved in a body fitted coordinate system using a homemade code based on control-volume approach, while all thermophysical properties of the nanofluid are dependent on considered temperature. The effects of different nanoparticle concentration and centrifugal forces on the temperature and pressure field have been examined in detail. The accordance of numerical results with experimental data expresses the accuracy of the employed numerical method for simulating flow and heat transfer in the curved pipes, as well as the accuracy of the single-phase model of the nanofluid. The Presented results indicated that both the nanoparticle and curvature effects improve the heat transfer characteristics dramatically, but at the expense of considerable increase in pressure drop. Furthermore, the results showed that in order to obtain the optimum operating conditions of nanofluids, different parameters such as heat transfer enhancement and pressure drop must be considered simultaneously. Finally, a method has been proposed to indicate the proper nanofluid and flow geometry for special practical applications.
