Flow and forced-convection characteristics of turbulent flow through parallel plates with periodic transverse ribs

Two general turbulence models, the standard k-ε model and the Reynolds stress model (RSM), were used to predict the forced convection of a fully developed turbulent flow through an assembly of two horizontally oriented parallel plates in the Reynolds number range 22,000 < Re_D < 94,000. The upper smooth plate was thermally insulated, whereas the bottom plate, attached with rectangular-cross-sectional ribs perpendicular to the mean air flow, was provided with a uniform heat flux. The ribs were uniformly spaced with the pitch-to-height ratio of p/e = 4, a height-to-hydraulic-diameter ratio of e/D = 0.25, and a width-to-height ratio of w/e = 2. The numerical approaches were based on the finite-volume technique. A second-order upwind scheme was applied in the calculation and a very fine mesh density was arranged in the regions near the wall boundaries. The SIMPLE algorithm was adopted to handle the pressure-velocity coupling in the calculation. Local Nusselt number distribution along the heated bottom ribbed surface was investigated, which was validated against corresponding experimental results conducted by Lorenz et al. [1]. It was found that in the simulation of the turbulent forced convection in this two-dimensional channel with a ribbed surface, the standard k-ε model had superiority over the Reynolds stress model. An anticlockwise vortex was found in the downstream region of a rib by using either of the two models; however, the length and relative strength of the vortex predicted by these two models were significantly different. Recirculating flow pattern was formed in the cavity between two adjacent ribs, while no reattachment of the mainstream flow was observed at the present pitch-to-height ratio of p/e= 4.