Development of Pressure-Sensitive Paint Systems for Low Speed Flows and Large Wind Tunnels

Abstract

Pressure-Sensitive Paint is an experimental technique that provides non-intrusive measurements of barometric pressure on wind tunnel model surfaces with high spatial resolution. Pressure-Sensitive Paint systems are commonly employed for academic research and several systems have been deployed in large transonic wind tunnels for production testing. Low speed wind tunnel measurements have been a target for deployment of Pressure-Sensitive Paint systems for over 15-years, however, quantitative pressure measurements in flows below Mach 0.3 have proven challenging. Over the past 7 years core Pressure-Sensitive Paint hardware such as CCD cameras, LEDs, image processing software, and temperature compensating Binary paints have been improved. Integration of this improved hardware into Pressure-Sensitive Paint systems has resulted in several successful demonstrations of Pressure-Sensitive Paint in low speed wind tunnels. These demonstrations include several small tunnel tests where the deviation between the pressure taps and Pressure-Sensitive Paint data is as low as 50-Pa. In larger production style tunnels, deviation between the pressure taps and Pressure-Sensitive Paint data of close to 100-Pa has been demonstrated. This paper includes an overview of the challenges associated with utilizing Pressure-Sensitive Paint in low speed wind tunnels and gives an outline of the equipment and experimental procedures that have produced high quality pressure data in low speed tunnels. Experimental data from measurement campaigns in a variety of large and small tunnels are presented to demonstrate the evolution of Pressure-Sensitive Paint for use at speeds between Mach 0.05 and Mach 0.3.