Thermographic laser Doppler velocimetry.

We propose a point measurement technique for simultaneous gas temperature and velocity measurement based on thermographic phosphor particles dispersed in the fluid. The flow velocity is determined from the frequency of light scattered by BaMgAl10O17:Eu2+ phosphor particles traversing the fringes like in conventional laser Doppler velocimetry. Flow temperatures are derived using a two-color ratio method applied to the phosphorescence from the same particles. This combined diagnostic technique is demonstrated with a temperature precision of 4%-10% in a heated air jet during steady operation for flow temperatures up to 624 K. The technique provides correlated vector-scalar data at high spatial and temporal resolution.