Description: 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. Recently, 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. This system interrogated the instantaneous pressure on the rotating blade at two azimuthal positions, an advancing and a retreating blade. We propose expanding this system for production testing in a larger wind tunnel, such as the Ames 80X120. 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. The hardware will be packaged in modules to facilitate quick installation and removal. Remote control of the system will improve productivity during testing. Finally, the accuracy and resolution of the system will be characterized with bench top experiments that operate at distances similar to those encountered in the 80X120 and on rotating devices. These experiments include unsteady pressures in acoustic boxes and jets impinging on rotating disks.

Benefits: There is considerable interest in measurements of unsteady pressure for evaluation of computational models and study of flow physics on hypersonic inlets, compressors, aeroelasticity, and rotorcraft aerodynamics. This system will provide advancement of the state-of-the-art in this field as the proposed research will develop a system for the measurement of continuous distributions unsteady pressure that require no physical modifications to the model and produces data with high spatial resolution. This technology could be deployed to wind tunnels at Ames, Glenn, and Langley for testing on a variety of programs that have need of unsteady pressure measurements. Specific applications include Rotorcraft Aerodynamics, Open Rotor, and Supersonic Inlets.

There is considerable interest in measurements of unsteady pressure for evaluation of computational models and study of flow physics on hypersonic inlets, compressors, aeroelasticity, and rotorcraft aerodynamics. This system will provide advancement of the state-of-the-art in this field as the proposed research will develop a system for the measurement of continuous distributions unsteady pressure that requires no physical modifications to the model and produces data with high spatial resolution. ISSI has sold several production PSP systems world-wide. There is significant interest among these customers in fast responding PSP. ISSI is currently involved in discussions with several commercial aircraft manufactures regarding the potential of a fast responding PSP system for flight testing. Development of this system for wind tunnel testing is seen as a first step in this process.