Journal of Applied Fluid Mechanics (Jan 2017)
Effect of Rayleigh Number with Rotation on Natural Convection in Differentially Heated Rotating Enclosure
Abstract
A Numerical study is carried out to investigate the effect of Rayleigh number with rotation on the flow and heat transfer characteristics in a differentially heated enclosure rotating about the horizontal axis. A Fortran Code developed based on FVM is used to discretize governing equations. Upwind difference scheme for convective terms and fully implicit scheme for transient terms are used. The SIMPLE algorithm is employed to couple pressure and velocities on staggered grid arrangement. The results were obtained for a Taylor number(〖10〗^3≤Ta≤〖10〗^5), rotation (10 rpm≤Ω≤25 rpm), and Rotational Rayleigh number (〖10〗^1≤〖Ra〗_w≤〖10〗^3) for two different Rayleigh number (1.3×〖10〗^4 & 1.1×〖10〗^5) with fixed Prandtl number (Pr=0.71). The results showed that the Coriolis force first tends to decrease heat transfer to a minimum and then starts to increase it with increase Rayleigh number and rotation. Minimum depends on Rayleigh number and corresponds to the balanced effects of interacting forces at the point of transition. At rotations, below minimum in average heat transfer, the circulations are counter clockwise. The direction of coriolis force is from core region, so both flow and heat transfer is reduced. When coriolis force is much larger than thermal buoyancy, motion is clockwise, and transition is prevented. coriolis force now tends to promote flow circulation and therefore increases the heat transfer. The frequency content of flow pattern reveals the structural changes in the flow and temperature fields with increasing Rayleigh number and rotation. The existence of different flow regimes dominated by these body forces complicates the time average heat transfer characteristics with a different behaviour in each of the regimes.
