Experiments on the Development of K-H Billows in Stratified Shear Layers

Abstract

The mechanism of K-H billow formation in stratified flows attracts scientist for many years and many attempts to investigate the phenomenon theoretically, experimentally and numerically have been conducted. The motive for research of this kind is to probe into microscale quantities pertinent to billows that may provide useful insights into the evolution of K-H billows in ocean, when combined with oceanic microstructure observations. The temporal evolution of K-H billows is reported in many previous experiments such as Thorpe (1968), De Silva et al. (1996) and Atsavapranee and Gharib (1997). A tilting tube entraining two layers has been used to produce K-H billows. Although such experiments are interesting and valuable, they do not allow detailed measurement of such important flow parameters as Reynolds stresses, density fluxes, kinetic energy dissipation and the local Richardson number. The present experiments are designed so that these parameters can be evaluated The measurements in a facility enabling a co- or/and a counter- flow of two layers of different densities and streamwise velocities are carried out to investigate the evolution of K-H billows in a stratified shear layer, from its “quaint” birth to “explosive” demise. The emphasis is placed on the initial evolution of the K-H billows. A series of homogeneous experiments was also performed as base-line cases to facilitate identification of the effects of stratification.