GRAVITY CURRENT ON A SLOPE IMPINGING ON A STRATIFIED INTERFACE

摘要

An experimental study of two-dimensional gravity currents impinging on a stratified interface in a two-layer stratified environment is presented. The currents are created by a continuous release of dense fluid along an inclined boundary (a ramp). The density of the gravity current is higher than that of the lower layer to ensure a penetrating gravity current is created and not a propagating intrusion along the interface. The inclination of the ramp is set at 6°. The stratified interface is located half way up the ramp. A chemical reaction (phenolphthalein) technique and Laser-Induced Fluorescence (LIF) are used to quantify the entrainment rate of the gravity current. Optics are positioned to create a laser sheet in the vicinity of the impingement region. The change of volume in the head of the gravity current quantifies the entrainment and mixing. The effect of slope has been determined previously by others (Britter and Linden 1980, Beghin et al., 1981). Here, the focus is to determine the specific effect of the stratification on the entrainment and mixing. In addition, knowledge of the internal structure of the gravity current is gained through LIF and Particle Image Velocimetry (PIV). Preliminary PIV measurements provide velocity and vorticity fields in the head of the gravity current before and after impingement.