Transition to turbulence in two-dimensional wakes

Abstract

A new technique is advanced for predicting the location of the laminar turbiiient transition zone in twodimensional wake flows. The technique is based on postulating a minimum turbulence Reynolds number required for sustaining the turbulence once it occurs. Using existing wake turbulence data and compressible laminar wake theory, the turbulence Reynolds number is then algebraically expressed in terms of freestream or wake edge conditions and integral properties. An example is calculated using laminar wake similarity, and a simple formula is found by which the transition distance is linked to the stream Mach number, the heat transfer rate, ratio of specific heats, and other parameters. Some of the existing transition data are utilized to find that the minimum or threshold turbulence Reynolds number is about 15, whereas other available data are compared and found in good agreement with the resulting formula.