Transition to turbulence in free shear-layers

Part 1 of this report presents an investigation of the transition to turbulence in free shear layers. A theoretical analysis is performed to drive a formula for predicting transition, based on the novel approach used earlier by the same investigators to predict transition in wakes and boundary layers. The formula so derived shows that the transition Reynolds number increases as the non-dimensional velocity ratio decreases, and also as the fast side Mach number and slow side total temperature are increased. An experiment to test the theory was performed; together with earlier transition data, the new data provide good support for the theory. However, a strong dependence of the transition Reynolds number on unit Reynolds number characterizes the available data, whereas the theory does not predict such dependence. In Part 2 of this report a brief account is given on the measurement of temperature fluctuations in a cooled compressible turbulent wake. The results endorse the novel detection technique utilized, and support theoretical predictions made earlier under this contract.