Hydroxyl-Tagging-Velocimetry Measurements of a Supersonic Flow over a Cavity

摘要

Hydroxyl-tagging-velocimetry measurements were made throughout the compressible flowfield of a Mach 2 airnflow over a cavity. The supersonic flowfield simulates the pilot region of scramjet combustion under nonreactingnconditions. In the hydroxyl-tagging-velocimetry method, ArF excimer laser (193 nm) beams pass through a humidngas flow, dissociating water to form a tagging grid of hydroxyl molecules. The hydroxyl-tagging-velocimetry gridndensity has been increased to 11 u0001 11 to yield up to 120 velocity vectors of the two-dimensional flow over a fixed timendelay of 2–3 u0001s. Instantaneous single-shot measurements of two-dimensional flow patterns were made in thennonreactingMach 2 flow over a wall cavity under low- and high-backpressure conditions. Single-shot profiles werenanalyzed to yield mean and rms deviation velocity profiles in the Mach 2 nonreacting flow. Compressibility greatlynreduces the growth rate of the supersonic shear layer formed at the edge of the cavity.Aset of velocity data (spanningnthe entire length of the cavity) for an open wall cavity in a supersonic flow under low- and high-backpressurenconditions was compiled for validation of computational fluid dynamics models.