Direct numerical simulation of bifurcating jets

The mechanisms leading to bifurcating jets are investigated by means of direct numerical simulation. Two distinct types of jets were obtained by applying a bi-modal perturbation at the nozzle. When forcing simultaneously the counter-rotating helical modes (flapping mode) with the same amplitude and the same frequency, the jet splits into two branches, taking a distinct Y-shape. A different evolution of the jet (Psi-shape) is observed when superposing the axisymmetric mode at the most amplified unstable frequency on the flapping mode with the same amplitude, but subharmonic frequency. In both cases a spectacular increase of the jet spreading is observed. (C) 2000 American Institute of Physics. [S1070-6631(00)00404-9].