An Extension to the Critical Flow of Stratford's Theory for Predicting the Turbulent Separation Position

Abstract

Stratford's theory for the prediction of separation of the turbulent boundary layer is modified so that it may be applicable to the critical flow, in which occurs a separation bubble followed by a turbulent reattachment. Calculations are based on the assumptions that (i) transition occurs at the laminar separation position which is predicted by the Stratford-Curle formula, and (ii) the velocity profile at the transition point is that of a turbulent zero-pressure-gradient flow which is taken as the “comparison” profile. The accuracy of the method is tested for experimental pressure distributions around a circular and an elliptical cylinder. It is seen that the theoretical positions of transition are in remarkably good agreement with the experiments, whereas those of turbulent separation (for critical flows) will tend somewhat to precede the experimental ones. An application to the free-streamline flow past a circular cylinder is also presented.