Surface tension effects on two-dimensional two-phase Kelvin-Helmholtz instabilities

The two-dimensional Kelvin-Helmholtz instability is studied using a lattice Boltzmann multi-phase model in the nearly incompressible limit. This study focuses on the effects of surface tension on the evolution of vortex pairi ng in a two-dimensional mixing layer. Several types of interface pinch-off are observed and the corresponding mechanisms are discussed. The contributi on of surface tension to the flow kinetic energy is mainly negative. Part o f this kinetic energy can be transformed to potential energy stored in the surface tension. The contribution of surface tension to the flow enstrophy is positive and small vortices are generated near interfaces. Broken interf aces and small vortices near interfaces dominate the late stage of flow fie lds with strong surface tension. (C) 2001 Published by Elsevier Science Ltd .