Spectral anemometry with an electrogasdynamic probe.

Abstract

This study involves the measurement of RMS velocities covering the frequency spectrum 25 to 20,000 hertz using an electro gas dynamic (EGD) probe. Previous work proved the feasibility of this investigation. The flow of air behind a circular cylinder was measured. The freestream velocity was 185 ft/sec. Charged water droplets entering the wake through a jet in the cylinder at sonic velocity acted as the media for conveying information to the probe. Hot-wire anemometer readings made in the same spectral range were used as the standard of comparison. However, these need further refinement. Small droplet formation was optimized by determination and control of the relative humidity of the freestream, steam temperature and steam pressure. Optimum droplet charge was then determined and controlled with corona voltage. A 10 to 15 decibel increase in high frequency response and stable performance resulted.