Kelvin-Helmholtz Instability in a Stratified Shear Flow

摘要

The evolution of the Kelvin-Helmholtz instability in stratified shear flows is studied. The presence of shear leads to instability, which is characterized by the spontaneous and rapid growth of almost stationary waves. Once the waves grow to an appreciable amplitude, they roll up into vortices. Data pertaining to wavelength, growth rate, and flow patterns are collected for various operating conditions. The critical velocity for the onset of the instability and the interface deformation is investigated. Experiments with three fluids of different density were performed. The middle layer is dyed for flow visualization. This visualization shows the development of the cores and the braids in the central layer. Elongation, rotation, and vortex pairing of the layer are also very well observed. The PHOENICS computer code was used to solve the equations which govern the experimental flows.