Large Eddy Simulation and Direct Numerical Simulation are applied to study the turbulent flow field in a wavy channel at two Prandtl numbers, Pr= 0.71 and Pr= 3.5, and Reynolds number Re-b = 10,000. The characteristics of the separated shear layer and the near wall recirculating zone are discussed in relation to the turbulent heat transfer. Special attention is paid to the behavior of the flow and thermal boundary layers and various turbulent characteristics and their effects on the distribution of the Nusselt number and friction coefficient in the separation and reattachment regions. The results indicate that the thickness of the thermal boundary layer rather than the turbulent fluctuations has a significant effect on the local variation of the averaged Nusselt number. The results are compared with Direct Numerical Simulation results of a plane channel at the same Reynolds number. (C) 2013 Elsevier Ltd. All rights reserved.