Stratified flow through outlets

Experimental and theoretical studies of stratified flow through outlets are reviewed, focusing on limiting height of aspiration, withdrawal layer thickness, and outflow concentration. First, a new non-dimensional criterion for limiting height of aspiration is proposed. It is found that this non-dimensional criterion changes only slightly for different kinds of selective withdrawal, including two-layer flow and linearly stratified flow through outlets at different levels. Therefore, if the salinity of density current and the outflow discharge are known, the limiting height of aspiration or the withdrawal layer thickness can be estimated. Second, characteristics of the outflow concentration of turbid density currents through outlets are studied. Based on the field observations in Sanmenxia Reservoir and Guanting Reservoir in China, as well as a number of laboratory experimental data from outlets in vertical walls and bottom outlets, a simplified model is developed to analyze the empirical relationship between outflow concentration and several critical parameters including outflow discharge, inflow sediment concentration, interface elevation, and outlet elevation. These research findings are readily applicable for outlet design, especially in sediment-laden waters.