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. During Phase I, a lens controller + pan/tilt stages with Ethernet control and presets was developed. This device will be used to control the field of view of the system remotely. Mitigation of motion blur at the tip was demonstrated using a galvanic mirror. A temperature measurement capability using TSP was added to the system to allow temperature corrections to be applied to the PSP data. Fast efficient data processing software that included automatic image registration and scripting of repetitive operations was investigated to speed up data processing. These new tools and software will be integrated into the data acquisition package and data processing package to improve accuracy and productivity during testing.

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.

This is a mature technology (TRL 8) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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