Direct comparison of hot-film probe and optical techniques for sensing shock-wave motion

Two independent shock-position-sensing techniques have been compared experimentally. One technique utilizes a hot-film probe controlled by a constant-temperature anemometer unit; the other method is strictly optical, employing a shadowgraph system and a line-scan TV camera. The techniques were employed simultaneously in a two-dimensional transonic diffuser flow with a shock wave. For the case of natural, random shock motion, the two systems produced similar results throughout the range of Mach numbers studied, in terms of both the amplitude and frequency content of the data signals. Tests were also conducted in which the shock wave was forced into periodic oscillation at several frequencies; excellent agreement was obtained between the average waveforms of the shock-motion data signals produced by the two techniques. Each technique possesses some definite advantages over the other; relative merits and applicabilities of the two methods are discussed.