El-Mehlawy, F.

Heat transfer in oscillating flows

The heat transfer in a sudden-expansion flow subjected to upstream periodic disturbances is investigated. In order to study the unsteady turbulent flow for the present symmetrical sudden-expansion flow, the phase-averaging technique of Hussain and Reynolds (1970) is used to derive the governing equations. The imposed periodic disturbances are found to increase the turbulent kinetic energy and the heat transfer rates at the wall. The phenomenon is discovered to be sensitive to the frequency of the imposed disturbances. At the optimum frequency and at a 3 percent disturbance level, the time-averaged heat transfer rate near the reattachment point can be increased by as much as 14 percent.