Supersonic Freestream Density Fluctuations from Focused Laser Differential Interferometry and Pitot-Probe Measurements

Focused laser differential interferometry (FLDI) is used to make freestream density fluctuation measurements in the von Kármán Gas Dynamics Facility (VKF) Wind Tunnel D at Arnold Engineering Development Complex. A comparison made between pitot-probe and FLDI after converting both pressure spectra. modification of Stainback Wagner’s theory, incorporating recent numerical results from Chaudhry et al., interpret pitot data, while a new inversion algorithm applied data. These methods interpretation assumption that tunnel disturbance environment dominated by acoustic Kovásznay mode, line with theoretical experimental evidence. Close agreement found two sets spectra, showing accurate quantitative data can be obtained FLDI, instrument extend spectra beyond bandwidth.