Luminescence-based Pressure and Strain Measurement for High-speed Fluid-structure Interactions

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The air flow over high-speed aircraft and rockets, particularly at supersonic speeds, can cause structural vibrations that may be detrimental to either the performance or the safety of the vehicle. These vibrations arise from large pressure fluctuations developing from the flow near the surface as well as from shock waves impinging the surface. The experimental determination of the location, magnitude and frequency of the pressure loads and their effect on the structural response are important to validate both theoretical and computational fluid-structure interaction models. This project will study and develop a novel approach to measure the combined surface pressure and strain using a fast-responding luminescent coating and high-speed digital cameras. The use of luminescence techniques in the science, engineering, and medical fields has seen substantial growth in recent years. The research will offer a robust learning environment to expose, energize, and recruit both undergraduate and graduate students. The goal of the proposed effort is to integrate two luminescent-based optical sensors?pressure sensitive paint and luminescent photoelastic coating?to measure the unsteady, distributed loads and strains on thin or deformable structures in high-speed flow. A successful effort will lead to a new tool for researchers and engineers to study fluid structure interactions in supersonic and eventually hypersonic flow where experimental data is often sparse. The approach is to exploit commonalities of the two measurement techniques. The average and the variance of luminescent emission intensity relative to camera polarization angle of the proposed binary pressure-strain coating are sensitive to surface pressure and strain, respectively. The advent of high-powered light-emitting diodes and digital cameras with micropolarizer lenses has enabled the possibility for this simultaneous full-field, time-dependent approach. The three year proposed effort would first characterize and demonstrate the approach in a controlled benchtop environment in year one, then expand to more challenging flow environments in on-campus supersonic flow facilities in year two and finally graduate to a demonstration at Sandia National Laboratories during the final year.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.