Abstract
Direct numerical simulations have been performed for turbulent heat and momentum transfer in porous channel flow, on which similar thermal and mechanical conditions are imposed. On the porous surface the transpiration is assumed to be proportional to the local pressure fluctuations (Jimenez et al. 2001 J. Fluid Mech. 442 89-117). Turbulent heat and momentum transfer is found to be significantly enhanced by the appearance of large-scale spanwise rolls from a linear instability of shear layer over the permeable wall. Weak but non-negligible dissimilarity, i.e., the higher Stanton number and the lower skin friction coefficient, is observed between heat and momentum transfer. The physical mechanism of this dissimilarity is interpreted in terms of the relevance of the spanwise rolls with their induced turbulent heat flux and Reynolds stress.
