Temperature Sensitive Paint Investigation of a Cylinder Induced Shockwave Boundary Layer Interaction

A urethane based temperature sensitive paint was employed to measure the surface temperature characteristics of both a cylinder perpendicular to a Mach 2.3 flow and the floor of the tunnel with varying gaps between the base of the cylinder and the tunnel floor. The first goal of this study was to determine the effectiveness of a temperature sensitive paint at providing quantitative and qualitative temperature data on supersonic flow interactions in a standard supersonic blow down wind tunnel. The second goal was to determine the heat transfer and surface temperature of the cylinder and the areas of the tunnel wall affected by the shock-wave/boundary-layer interaction caused by the cylinder. For calibration, the response of the paint to temperature changes was determined using a vacuum chamber with the ability to cool and heat a sample of the paint and measure the intensity change of the paint. The temperature of the paint was recorded with thermocouples and the intensity of the luminescence from the paint was recorded at regular intervals. The paint was then employed on the floor of the wind tunnel ahead of the cylinder to evaluate the effect on the surface temperature ahead of the cylinder. The results showed that the paint can react quickly to the temperature rise caused by the shock-wave/boundary-layer interaction qualitatively. However, fully time-resolved temperature changes in a quantitative sense are not possible due to the full response of the paint to a temperature change taking approximately 750 ms. Encouraged by these results the paint was applied to the surface of the cylinder itself to capture the temperature characteristics of the jet created by the Edney interaction. The results showed that the mild steel cylinder was too strongly affected by its low Biot number to determine discernable temperature changes. The cylinder was then insulated by polytetrafluoroethylene and showed promising results for the qualitative nature of the surface temperature distribution created by the interaction. It was concluded that the paint used is an effective fluid diagnostic for investigating this interaction and that gap effects caused a change in the heat transfer due to the interaction but did not affect the location of the interaction’s characteristic features.