A molecular filter based technique for simultaneous measurements of velocity and thermodynamic properties

A molecular filter based flow diagnostic technique termed Filtered Angularly-Resolved Raleigh Scattering (FARRS) is used to measure velocity, density, and temperature simultaneously. The technique uses an anamorphic optical system to record the Rayleigh scattered signal viewed at different angles and focused onto an intensified CCD camera. The experimentally obtained intensity versus viewing angle profiles are then combined with a computational model to solve for the velocity, density, and temperature. The technique was used in a supersonic axisymmetric jet operated at a variety of flow conditions from Mach 1 to Mach 2.3. Three different FARRS optical arrangements were investigated. The first arrangement was usedto make average measurements in the core of the jet where the velocity and thermodynamic conditions are well known. The measured values are within 11% for the velocity and 7% for the other thermodynamic properties. The second optical arrangement was used to measure three components of velocity in an isothermal supersonic jet where the temperature is approximately constant across the mixing layer. Both average velocity and turbulence intensities were determined. The final optical system measures the instantaneous streamwise velocity, density and temperature simultaneously. For all the FARRS cases, the optical configurations are described and methods of backing out the velocity, density, and temperature from the experimental intensity profiles are discussed.