Optical Measurements of Pressure and Shear in a Plasma

Over the past several years there has been much interest in the use of plasmas for flow control and drag reduction. Efforts to verify the theoretical models of these physical effects are dependent on experimental data, unfortunately traditional sensors such as pressure transducers and thermocouples are not always compatible with this experimental environment. Furthermore, the spatial resolution of these embedded sensors is limited. In an effort to acquire high-spatial resolution measurements of temperature, pressure, and shear on the surface of a model in the presence of plasma we have applied newer optical techniques such as Temperatureand Pressure-Sensitive Paint and Shear and Stress Sensitive Films. These techniques produce high-spatial resolution maps of temperature, pressure, and shear on the model surface. Since these are image-based techniques, no electrical hardware resides on the model. This minimizes the potential interference with the measurements by the plasma environment while simplifying model construction. Each technique will be discussed and the results of several tests in the Mach 5 tunnel at WrightPatterson Air Force Base will be presented. These results demonstrate the capability of these optical diagnostics in this challenging flow field.