Calibration and Optimization of Constant Voltage Hot-Wire Anemometer in Hypersonic Flows

摘要

Freestream and boundary layer measurements are made in a supersonic flow using both constant temperature (CTA) and constant voltage (CVA) anemometry. The performance of both anemometers is systematically made by operating the same hot-wire under identical conditions and applying post-test software corrections to the fluctuating measurements. In the case of the CVA the in situ time constant of the hot wire is measured to compensate the measured CVA output. The measurements show that when the signal-to-noise ratio is greater than one for both systems, the results are in very good agreement. The measurements of turbulence intensities are also in good agreement with previous studies. However the frequency at which noise dominates is lower for the CTA. Thus the CVA bandwidth is very much larger than that of the CTA. The amplitude roll-off at high frequencies is as theoretically expected. Thus it is desirable to obtain new quantitative turbulence measurements with larger bandwidth using the CVA. A rapid and automated stepping of the wire overheats is also developed for the CVA. This is an advancement over previous works that employed CTA, as the latter approach has a different bandwidth at each overheat, whereas the CVA has a fixed bandwidth. The rapid scanning method is then used to obtain calibrated measurements in a short duration wind tunnel.