Optical Diagnostics System for Very-High-Speed Velocimetry and Thermometry in Hypersonic Ground Test Facilities

Speckodyne Corporation, in collaboration with Texas A&M University (TAMU), proposes to develop a very high-speed multiparameter optical diagnostic system for nonintrusive measurements of hypersonic flow velocity and nonequilibrium temperature at continuous repetition rates of up to and exceeding 100kHz.  This innovation addresses the need for enhanced precision and resolution measurement instrumentation at USAF AEDC Hypervelocity Tunnel 9, VKF and other hypersonic ground test facilities. Ultrafast measurement systems will provide crucial experimental data for validating and refining Computational Fluid Dynamics (CFD) models and understanding the small-scale dynamics of freestream and turbulent boundary layer flow in the broadband disturbance environment of conventional wind tunnels. Our fully integrated hardware and software and high-speed solution implements two state-of-the art nonintrusive optical diagnostic techniques: Femtosecond Laser Electronic Excitation Tagging (FLEET) velocimetry, and hybrid picosecond/femtosecond Coherent Anti-Stokes Raman Scattering (CARS) nonequilibrium thermometry.  Both techniques have already been demonstrated at Tunnel 9 at 1kHz repetition rate in Mach 14 and 18 nitrogen flow. The Phase I effort will demonstrate the feasibility of measuring velocity at 100 kHz and rotational/vibrational temperature at multi-kHz rate under variable flow pressure and nonequilibrium conditions characteristic of AEDC wind tunnels. The proof-of-concept demonstration will evaluate very high-speed FLEET velocimetry and hybrid CARS thermometry both in laboratory and in large-scale hypersonic ground test facilities at TAMU. The results will be used to optimize the solution and to build a preliminary plan for system development which will guide the Phase II effort focused on prototype development, implementation and demonstration at the AEDC Tunnel 9 facility. The broader/commercial impact of this project is in providing advanced measurement instrumentation for hypersonic wind tunnels that bridge the gap between aerodynamic testing and CFD simulations to ultimately accelerate the development of the next generation of our nation's hypersonic vehicles and defense technologies.