MIXING IN A CONFINED TURBULENT IMPINGING JET USING PLANAR LASER-INDUCED FLUORESCENCE

The non-intrusive Planar Laser-Induced Fluorescence (PLIF) technique w as applied to the study of the mixing of a turbulent water jet impingi ng orthogonally onto a flat surface. A procedure for calibrating the s ystem at each pixel of a CCD camera array was first developed and test ed. Postprocessing of the PLIF data gave quantitative results of good quality. The mixing at the entrance of the deflection zone was also in vestigated. Average concentration fields in the centre plane of the je t were calculated and compared with Large Eddy Simulations (LES) and a lso with data from the literature. Probability density functions, spac e coefficients of correlation and radial concentration fluctuation pro files were calculated to further quantify the spreading of the jet, bo th in the free and deflection zones. Inside the deflection region, a s light tendency towards intensified mixing at the outer edge of the jet was found. This was attributed to a deceleration of the fluid which r esulted in accelerated diffusion.