Effects of confinement on the temporal instability of gas jets injected inviscous liquids

A temporal linear stability analysis of an inviscid incompressible gas jet injected into a coflowing viscous liquid confined within a tube was conduct ed to study the growth of small disturbances that lead to the breakup of th e gas jet. For low-viscosity liquids, the confinement of the liquid jet did not affect the growth rates of the gas-jet disturbances. However, for high viscosity liquids, confining the liquid jet results in a significant incre ase in the disturbance growth rate and the range of unstable wave numbers. Also, for small ratios of the liquid jet diameter to gas jet diameter, the change in disturbance growth rate with Weber number is small. The effect of Weber number becomes significant only at large values of the diameter rati o. (C) 2000 American Institute of Physics. [S1070- 6631(99)02712-9].