Laser Doppler velocimeter measurements in unsteady, separated, transonic diffuser flows

Abstract

A laser Doppler velocimeter was used to measure the stream wise velocity component in unsteady separated flowfields in a two-dimensional transonic diffuser with and without externally induced periodic fluctuations. Results are also presented for fully attached, unsteady, unexcited flow. The time-dependent perturbation flowfield associated with the external excitation was determined throughout the subsonic region for a case with shock-induced separation. The results indicate that a transverse, wavelike motion of the boundary-layer/coreflow interface is an important aspect of the overall oscillations and overwhelms effects associated with acousticwave propagation.