Density cross sections and velocity profiles in high-speed air by UV Rayleigh scattering and by Raman excitation + laser induced electronic fluorescence (RELIEF) Available to Purchase

Two new techniques for measuring spatially resolved features in high speed air flows are presented. Rayleigh scattering with ultraviolet light yields intensities which are high enough give instantaneous cross sectional images of atmospheric density air with a relatively low energy laser. These images freeze turbulent features and shock structure. They can be used observe shock wave/ boundary layer interactions and to construct spatial correlations which show the average size and shape of these turbulent features as well as the correlated motion of shock structure. Using the RELIEF method, we are able to instantaneously write lines or shaped volume elements into the flow and interrogate them at a later time. This enables us to record instantaneous velocity profiles, each of which gives a frozen image of the turbulent motion of the flow. From numerous such images the average velocity, turbulence intensity and cross stream velocity correlation can be found.