TEMPORAL EVOLUTION OF PERIODIC DISTURBANCES IN 2-LAYER COUETTE-FLOW

The time-dependent motion for a two-layer Couette flow consisting of f luids of different viscosities is simulated numerically by using an al gorithm based on the Volume of Fluid (VOF) method. Interfacial tension is included via a continuous surface force (CSF) algorithm. The algor ithm is fine-tuned to handle the motion which is driven by a shear-ind uced interfacial instability due to the viscosity stratification. The code is validated against linear theory. Two prototypical situations a re presented, one at a moderately high Reynolds number and the other a t a lower Reynolds number. The initial condition is seeded with the ei genmode of largest growth rate, with amplitudes that are varied from t hose that capture the linear regime to larger values for nonlinear reg imes. Issues of free surface advection and viscosity interpolation are discussed. The onset of nonlinearity occurs at the interface and is q uadratic, followed by wave steepening. (C) 1997 Academic Press.