Hypersonic FLEET velocimetry and uncertainty characterization in a tripped boundary layer

Abstract

Femtosecond laser electronic excitation tagging (FLEET) velocimetry is applied in a hypersonic boundary layer behind an array of turbulence-inducing trips. One-dimensional mean velocity and root-mean-square (RMS) of velocity fluctuation profiles are extracted from FLEET emissions oriented across a test article and through a boundary layer in two test campaigns spanning 21 tunnel runs. The Texas A&M University Actively Controlled Expansion tunnel in which FLEET was performed operates near Mach 6.0 with Reynolds number near 6 ×106 m-1 and a working fluid of air at a density near 2.5 × 10-2 kg/m3. Calibration curves are generated using synthetic images to estimate the error in the mean velocity due to emission decay and the error in the RMS velocity fluctuation due to imprecision. The boundary layer behind an array of turbulence-inducing trips is documented to show the breakdown of coherent structures. FLEET velocimetry is compared to the tunnel data acquisition system, Vibrationally Excited Nitric Oxide Monitoring (VENOM) results, and Reynolds-Averaged Navier-Stokes Computational Fluid Dynamics to verify results.