Determination and optimization of frequency response of constant temperature hot-wire anemometers in supersonic flows

In order to achieve turbulence measurements in supersonic flows the frequency response of CTA is tested and improved. A fast and convenient technique to determine electrically the frequency response is proposed; the response is also tested by direct heating of the wire by means of a laser beam. The two techniques are in good agreement. Under certain experimental conditions (M=2, Reφ=400) it is possible to use CTA with a satisfactory frequency response up to 250 kHz and overheat ratios down to 0.07. In these severe operating conditions, the square-wave test technique seems to be not sufficient to ensure optimum settings and it is necessary to use symmetrical bridges with fine adjustment of offset voltage.