Laser velocimeter developments for surveying thin boundary layers in a Mach 6 high Reynolds number flow

Two-component fringe-counter type laser velocimeter techniques were developed to measure model boundary layer velocity profiles in a Mach 6 High Reynolds Number Wind Tunnel. Free stream velocities were approximately 3500 feet per second. Boundary layers as thin as 0.20 inches were surveyed to within .007 inches of the surface of a 16 inch wide sharp leading edge flat plate. Optical, signal processing, and computational techniques and equipment are discussed. Artificial flow field seeding of 1.0 to 2.0 micron particles was achieved in the facility stagnation section. This test program was conducted at stagnation pressures of 700 and 1400 psia. The stagnation temperature for the entire program was 1100 degrees R. Data rates of 2,000 per second were realized through the velocimeter test volume.