Turbularization of the Stokes layer over a transpiring surface

Abstract

In this work, the onset of turbulence inside a rectangular chamber is investigated, with and without side-wall injection, in the presence of an oscillatory pressure gradient. Three techniques are used to define the transition from laminar to turbulent regimes: statistical analysis, spectral analysis, and flow visualization. Calibrated hot film anemometry and a computer data acquisition system are used to record and analyze acoustic flow data. Four classifications of flow regimes are achieved: (a) laminar, (b) distorted laminar, (3) weakly turbulent, and (4) conditionally turbulent. A fully turbulent flow could not develop at any of the driving frequencies tested. A relaminarization always occurs within a cycle. Transition between flow regimes is assessed from the standard deviation of velocity data correlated as a function of acoustic Reynolds number. Transition in oscillatory flow with side-wall injection is found to be reproducible at the same critical value of the acoustic Reynolds number, Re A = 195.