Interactive natural convection heat transfer froma pair of horizontally-parallel cylinders

Abstract

Interactive laminar natrual convection about a pair of horizontally-parallel cylinders, either in a vertical or horizontal arrangement, was numerically studied by solving the finite difference form of the Navier-Stokes and energy equations. The heat transfer characteristics of the cylinders, with their cross sectional form limited to either circle or square, was investigated in the present study with emphasis on illuminating the mutual thermal interaction. Difficulty associated with the complicated multi-body domain was resolved by using the boundary-fitted coordinates of multiblock form. To avoid the grid singularity in the region of high shear flow in the case of circular cylinders, an additional body-fitted grid system had to be embedded inside of the external one, with grid overlapping in between. Separated flow was found in the natural convection in this case on the top of the upper cylinder as it was impinged by the buoyant plume from the lower one. The powerful streamfunction-vorticity formulation, which could not have been used for the multiply connected bodies so far, is now made feasible by introducing a new pressure constraint in determining the wall streamfunction uniquely. This approach presents tremendous computational efficiency over the conventional primitive variable formulation. Mach-Zehnder interferometric study was also performed concurrently to the computational investigation to provide experimental data comparable to the computed results.