Effect of a circular cylinder's location on natural convection in a rhombus enclosure

Based on numerical simulations using the immersed boundary method (IBM), results for natural convection in a rhombus enclosure with an inner circular cylinder and a Prandtl number Pr = 0.7 are presented. This simulation spans four decades of Rayleigh number Ra, from 10(3) to 10(7). The inner circular cylinder's location is vertically changed along the rhombus enclosure's centerline. We investigate the effects of both the inner cylinder's location in the rhombus enclosure and buoyancy-induced convection on heat transfer and fluid flow. With respect to the cylinder's location and the Rayleigh number, the thermal and flow field is categorized into three regimes: steady-symmetric, steady-asymmetric, and unsteady-asymmetric. The map of thermal and flow regimes is presented as a function of the cylinder's location and of the Rayleigh number. Detailed analysis results for the distribution of streamlines, isotherms, and Nusselt numbers are also presented in this paper. (C) 2014 Elsevier Ltd. All rights reserved.