Measurement of mean velocity and turbulence in supersonic boundary layers, shock waves and free jets by laser anemometry

Abstract

Velocity profiles and turbulence levels have been investigated in a Mach 2 wind-tunnel using a laser anemometer which directly measures the Doppler frequency shift in the scattered laser light. The experiments were performed with the wind-tunnel operating at normal humidity. However, ice particles were always produced in the supersonic throat, making artificial seeding unnecessary. These ice particles proved to be excellent light scattering centres, and were found to respond to the rapid velocity change occurring in an oblique shock wave in a distance <0.01 cm, from which the ice particle size was calculated to be <0.1μ.