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.