Fast Responding Pressure-Sensitive Paint for Large-Scale Wind Tunnel Testing

The proposed work focuses on implementing fast-response pressure-sensitive paint for measurements of unsteady pressure in rotorcraft applications. Significant rotorcraft problems such as dynamic stall, rotor blade loads in forward flight, and blade-vortex interaction all have significant unsteady pressure oscillations that must be resolved in order to understand the underlying physics. Installation of pressure transducers is difficult and expensive on rotorcraft models, and the resulting data has limited spatial resolution. Application of a fast-responding pressure-sensitive paint should provide unsteady surface pressure distributed over the blade surface. Fast PSP measurements have been demonstrated at NASA Langley on a 2-meter rotor model in hover and in forward flight by the ISSI/OSU team using two single camera systems. More recently, measurements were conducted in forward flight using multiple cameras and lasers at two azimuthal positions. We propose expanding this system for production testing. This will be accomplished by adding remote control of the system interrogation region using remote focus/zoom/aperture lenses and pan/tilt stages combined with Ethernet hardware to control the systems remotely. Motion blur will be addressed using both a rotating mirror and de-convolution software. Data processing software will be customized to allow scripting of repetitive operations to speed up data processing. Finally, a temperature measurement capability will be added to the system to allow temperature corrections to be applied to the PSP data. These modifications to the system will improve accuracy and productivity during testing.