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An experimental method for time resolved concentration measurements in the near field of a transient starting turbulent air jet is presented. Planar Laser Mie Scattering (PLMS) using DEHS droplets produced by a Laskin nozzle as tracers of concentration is applied on an air jet with Reynolds number of 62.000 and is recorded with 10.000 frames per second. A jet penetration of about 20 nozzle diameters into the ambient environment is resolved with more than 100 frames. A linear response between grey scale values and concentration is found for mixtures up to 13% of the air-particle flow from the Laskin nozzle mixed with clean air. The calibration is based on images with no particles and images with a homogeneous particle concentration. A correction for light scattered by particles outside the laser sheet is proposed. The experimental results agree well with mean concentration measured with other techniques.
Hartz et al. (Mon,) studied this question.