CONCENTRATION FLUX MEASUREMENTS OF A SCALAR QUANTITY IN TURBULENT FLOWS

A method for determination of velocity-concentration fluxes is present ed that combines two conventional imaging techniques, particle image v elocimetry (P.I.V.) and planar laser-induced fluorescence (P.L.I.F.). The passive concentration jet was a perfect mixture of fluorescein dye and solid particles submerged in an isotropic homogeneous turbulent c hannel. The light intensity fluoresced by the dye and the light intens ity scattered by the particles were recorded separately on two synchro nized cameras by using appropriate high and low-pass filters. Two diff erent sets of images were thus obtained simultaneously. Once digitized and numerically processed, they provide the space and time evolution of velocity and concentration instantaneous fields. Thus, the velocity -concentration correlations can easily be determined. The statistical results for velocity and concentration are compared with classical res ults in order to validate the technique. We finally report some result s giving velocity-concentration fluxes.