The Effect of Unsteady Compression and Expansion Waves on a Compressible Boundary Layer

This abstract summarizes the results of an investigation into the effects of finite amplitude acoustic disturbances or weak compression and expansion waves on compressible boundary layers. Specifically, the goal is to provide a theoretical model which predicts the increased heat transfer and skin friction associated with unsteady pressure disturbances. These pressure disturbances, which are produced by combustion instabilities, are present in most combustors. The magnitude of the fluctuating component relative to the stagnation pressure varies from the low acoustic range (0.05 %) to the weak shock range (5 %). The frequencies range from a few hundred Hz. for the longitudinal mode to a few thousand Hz. for the transverse mode. A simple but accurate theoretical model which predicts the enhanced heat transfer and skin friction for a wide range of frequencies and magnitudes is presented. The formulation yielded an unexpected result in that an approximate analytical solution is possible for the laminar flow case.Copyright © 1988 by ASME