Numerical study of periodically fully-developed flow and heat transfer in channels with periodic semi-circular tube

The periodically fully-developed flow and heat transfer in channels with periodic semi-circular tube is studied numerically by the direct numerical simulation (DNS), the large eddy simulation (LES), and the Reynolds stress model (RSM). When the Reynolds number is between 3000 and 25000, the Nusselt number obtained by the RSM is closer to the experimental results than the results obtained from other turbulence models. The nonlinear characteristics of flow and heat transfer is revealed based on the results of numerical simulation. When Reynolds number is high, the geometric structure and boundary conditions of the channel are symmetric, but the flow field in the channel is asymmetric. With increasing Reynolds number, the flow and heat transfer in channels experiences steady state, periodic oscillations, and finally chaos. Moreover, Nusselt number increases gradually with the decrease of tube spacing at the same Reynolds number. Among all cases considered in this paper, the maximum Nusselt number is 15.22 times of the minimum Nusselt number.