Unsteady Boundary Layers with Flow Reversal and the Associated Heat-Transfer Problem

Abstract

Two specific examples of nonseparating unsteady boundary layers with local flow reversal, and their associated thermal boundary layers, are constructed from the class of semisimilar solutions. The governing equations are so written that proven numerical schemes for steady boundary layers can be applied without modification. The results show no drastic change of heat transfer at flow reversal, invalidating the usual concept of Reynolds analogy. The structure of the equations meanwhile suggests a separation criterion which clearly accounts for the unsteady effects.