Experimental Study of Turbulent Offset Jets

Proper orthogonal decomposition and swirl strength analyses were applied to turbulent offset jets at a Reynolds number based on a maximum mean jet exit velocity and nozzle diameter of 10000. The offset jets are water jets flowing into quiescent water media and have offset heights (h) based on nozzle diameter (d) of h/d = 2 and 4. The data were obtained using a particle image velocimetry (PIV) technique. The results indicate that the reconstruction of the turbulent quantities is so effective that the reconstructed profiles collapsed on the ensemble PIV data using only the first 25 POD modes. The offset height did not have any effect on the convergence of the reconstructed profiles. The mean swirl strength is non-zero at any location about 3 5 % of the time. The higher offset height has a lower percentage of non-zero swirl in the inner shear layer.