Laser Doppler velocimetry measurements across a normal shock in transonic flow

Abstract

One-dimensional laser-Doppler velocimetry measurements were taken with standard optics in back scatter mode across a normal shock at a Mach number of 1.35. Back pressure on a blow-down supersonic tunnel was controlled to place a normal shock in a 4 by 4 inch test section and schlieren visualization techniques were used to verify and record shock position and behavior. Velocity surveys were taken across the shock, using various filtering techniques, in an attempt to quantify shock unsteadiness. Additional surveys were performed to further characterize the flow in the test section. The velocity surveys upstream and downstream of the shock compared favorably with pressure and temperature data and normal shock relations. Surveys across the shock indicated distinct and repeatable velocity patterns, and the measured location of the shock matched schlieren photographs