A Numerical Study of Breaking Kelvin-Helmholtz Billows using a Reynolds-Stress Turbulence Closure Model

Abstract

A two-dimensional numerical study of breaking Kelvin-Helmholtz billows is presented. The turbulent breaking process is modeled using second-order closure methods to describe the small-wale turbulence, while the large-scale billow itself is calculated explicitly as a two-dimensional flow. The numerical results give detailed predictions of turbulence levels and time scales, and are consistent with laboratory and atmospheric observations. Two general predictions of the model are that the structure of turbulent temperature fluctuations is very different from that of the velocity fluctuations, the former being much more striated, and that the time scale of the growth and breaking process is virtually completely determined by the initial velocity shear.