HYPERSONIC FLOW VISUALIZATION USING THE GLOW DISCHARGE TECHNIQUE.

The use of an electrical discharge to obtain visualization in hypersonic flow is considered. The experimental effort was conducted in the ARL hypersonics facility using the three-inch and four-inch hypersonic wind tunnels. The electrical discharge is identified as a classical glow discharge, and its characteristics are discussed. The quality of visualization is found to depend upon electrode position relative to the stream, and model position relative to the transverse plane containing the electrodes. The effect of electrode polarity is investigated and found to be critical. The validity of the results determined by using schlieren results and Van Dykes numerical solution for axially symmetric shock wave shapes. The effectiveness of the technique is determined by comparison of the results with those obtained using schlieren. Tests were conducted to determine the effect of the discharge on model temperature and pressure, as well as on the flow pattern as portrayed by schlieren photography. Author