VISUALIZATION AND ANALYSIS OF ACCELERATING TRANSONIC FLOW OVER TYPICAL LAUNCH VEHICLE MODEL USING IMAGE PROCESSING

Abstract

The formation and transit of the Lambda-shock system that occurs over the payload region of a launch vehicle at transonic Mach numbers have been captured using high-speed shadowgraphy and unsteady pressure measurements. The test section Mach number (M) was varied from 0.85 to 0.95 continuously. Analyses based on image processing indicate systematic downstream movement of the shock system until M = 0.92 and rapid oscillations upstream and downstream of the mean position at higher M. Unsteady pressure measurements indicate large fluctuations in this range, suggesting localized alternating flow over the payload. Pressure fluctuations obtained during Mach-sweep mode indicate higher values as compared to results at constant Mach number at the same angle of attack (α), suggesting that (dM/dt) is an important parameter that needs to be properly simulated in wind tunnel tests in order to characterize the flight performance of launch vehicles at transonic Mach numbers.