CONTRIBUTION TO THE INSTABILITY OF LAMINAR SEPARATING FLOWS ALONG AXISYMMETRICAL BODIES .1. EXPERIMENT AND COMPARISON WITH THEORY

A wind-tunnel study for the instability of an axisymmetric backward-fa cing step flow was carried out using disturbances excited by sound. Th e data, which were obtained, indicate that the axisymmetry of the sepa rated boundary layer results in a decrease of the instability, compare d to that in plane two-dimensional separating layers. The comparison o f the data with theoretical results show that calculations of the inst ability of the axisymmetric flow with the parallel flow approximation predict fairly well the stability characteristics, determined in the e xperiment; however, the distributions of the u-fluctuations show diffe rences.