Some interesting features of plane turbulent jets

Experimental data are reported to show that improvements can be made in the prediction of the asymptotic decay rates of plane turbulent jets by configuring the velocity scale on the basis of the asymptotic jet momentum. The data were obtained using a two-component LDA in separate single and dual-jet trials. It was found that for a single jet the kinetic momentum flux was not preserved, although the decay rate could be predicted by proper characterization of the jet exit velocity. A relationship is defined between the growth and decay rates. The length scale is defined in terms of the exit volume flow rate for the case of merging jets. After merging, the twin jet has a length scale comparable to a single jet due to removal of large eddies from the flow. Reduction of the eddies lowers the entrainment rate and the Reynolds shear stress.