Heat transfer enhancement in oscillatory flow in channel with periodically upper and lower walls mounted obstacles

A numerical investigation is conducted in a rectangular channel with heated obstacles mounted alternatively on the upper and lower walls. Time-dependent two dimensional laminar flow with constant thermophysical properties is assumed for air at three values of the Reynolds number (50, 500 and 1000). A detailed analysis is carried out to investigate flow pattern and Nusselt number. Streamwise periodic contraction-expansion of the cross-section induces bifurcation from steady to unsteady flow. In the unsteady state, a self-sustained periodic oscillatory flow occurs. It is also found that a travelling wave generated by the vortex shedding contributes mainly to heat transfer enhancement. (c) 2006 Published by Elsevier Inc.