INSTABILITY OF A LIQUID JET SUBJECT TO DISTURBANCES COMPOSED OF 2 WAVE-NUMBERS

The instability of viscous capillary jets subject to disturbances cons isting of two superposed wavenumbers, and for large disturbance amplit udes is investigated. Disturbances composed of the superposition of a fundamental disturbance (first harmonic) with either its second or thi rd harmonic are used. The influence of the wavenumber of the fundament al disturbance on the jet breakup is studied for a disturbance compose d of a first harmonic with an initial non-dimensional amplitude of eps ilon(1) = 0.01 and a second harmonic with an initial non-dimensional a mplitude of epsilon(2) = 0.05. The influence of the initial amplitudes of the first and second harmonics on the jet breakup is studied for t wo non-dimensional wavenumbers of the fundamental (first harmonic): k = 0.45 and k = 0.7; the second harmonic is unstable in the former and stable in the latter case. The effect of an added third harmonic is st udied only for k = 0.45 but for a wide range of initial amplitudes. Al l cases are studied for an in-phase and a 180 degrees out-of-phase sup erposition of the two waves. The nonlinear interaction between the two waves results in the formation of a variety of drop sizes and shapes. The breakup times can be controlled within a wide range using this te chnique.