An asymptotic theory for the periodic turbulent boundary layer in zero mean pressure gradient

Abstract

An asymptotic theory valid for large Reynolds number is developed for describing the oscillatory properties of a turbulent boundary layer in a free stream whose velocity varies harmonically with time around a non-zero mean value. The theory identifies two frequency parameters in terms of which four different regimes of oscillation frequency are defined. Similarity laws are identified for each of these frequency regimes and for the different layers of the periodic boundary layer. The theory seems to bring together the available data on unsteady wall bounded flows into a general framework.