Laser Doppler Velocimeter Application in Supersonic Boundary-Layer Flow

Abstract : Laser Doppler velocimeter techniques have been investigated for nonintrusive measurements of cone boundary-layer mean-velocity profiles in supersonic flow. The investigation was performed in the AEDC Supersonic Wind Tunnel (A) at a free-stream Mach number of 4, using olive-oil droplets to seed the tunnel flow. The basis for the evaluation of the LDV results was a set of velocity profiles obtained using conventional probing techniques. Laminar, transitional, and turbulent boundary layers on a 7-deg (half-angle) sharp-cone model were included in this study. The results obtained in this investigation demonstrate that mean-velocity profiles can be obtained within acceptable limits of uncertainty provided (1) seed particles of appropriate size are found in tunnel flow or can be added to the flow and (2) a systematic editing procedure is available, when the results are evaluated, to eliminate velocities of relatively low probability and effects of spurious noise.