Bouncy Fluid Jets

Contrary to intuition, free f\mbox{}luid jets can sometimes ``bounce'' of\mbox{}f each other upon collision, due to an entrained air f\mbox{}ilm that keeps them separated. So far, there have only been a few descriptive studies of bouncing jets, since the f\mbox{}irst recorded observation by Rayleigh more than a century ago. We present a quantitative investigation of non-coalescence in jets of same f\mbox{}luid upon an oblique collision. Using a simple experimental set-up, we carried out a parametric study of the bouncing jets by varying the jet diameter, velocity, angle of inclination and f\mbox{}luid viscosity. Our results reveal a scaling law for the contact time of bouncing jets. We further investigate the transition of colliding jets from non-coalescence to coalescence, which seems to be caused by instability of the f\mbox{}luid interface. A dimensionless parameter, which is a function of the Normal Weber Number, Normal Reynolds Number and the angle of inclination of the jets, quantitatively dictates the transition.