Doppler global velocimeter development for large wind tunnels

An optical, laser-based flow-field measurement technique for large wind tunnels is described. The technique, Doppler global velocimetry (DGV), uses laser sheet illumination and digital imaging to rapidly measure velocity distributions over large planar regions of the flow. DGV measures the Doppler shift of laser light scattered by aerosol particles that are added to the flow. An optical filter cell containing iodine vapour functions as a sensitive frequency discriminator that converts Doppler frequency to image intensity. The procedure used to process image intensity to yield three-component velocity maps is described. Measurement uncertainty is analysed and discussed, and sample measurements are presented.