Direct numerical simulations of three-dimensional flow and augmented convection in a channel with symmetric, transverse grooves on two opposite walls are performed using the spectral element technique. The flow is driven by a constant pressure gradient. A method employing an exponentially decaying temperature scale is developed and used to calculate the fully developed heat transfer coefficient for constant temperature boundary conditions. Results are presented for the Reynolds number range 180 < Re < 1175.
A series of flow transitions is observed as the Reynolds number is increased, from steady two-dimensional flow, to traveling two and three-dimensional wave structures, and finally to three-dimensional mixing. Periodic ejection of slow moving fluid from the grooves causes significant flow rate unsteadiness. Three-dimensional simulations predict friction factor and Nusselt number values to within 20% of measured values over the narrow Reynolds number range where overlapping data exists. Two-dimensional simulations are found to be inadequate to calculate transport in this channel for Re > 400.