Prediction of critical submergence in a two-layer-stratified fluid flow

Abstract

This study examines the critical submergence of a pipe intake located in a two layer-stratified flow. The critical submergence for a vertically downward flowing pipe intake in a two-layer stratified fluid field is defined as the vertical distance of the interface of the fluid layers to the intake level for which the upper fluid just enters the intake. The available potential flow solution-based theory developed for the critical submergence of an intake located in a single fluid flow (with no stratification) is utilized to predict the critical submergence for an intake located in a two-layer-stratified flow. It is shown that whole boundary blockage effects may be disregarded, and an imaginary complete critical spherical sink surface (CSSS) can be used for the prediction of the critical submergence. The results of several available experimental studies indicate that the velocity at the imaginary complete CSSS is a constant for a given geometrical and flow conditions and it can be obtained by conducting a few experiments. Since this approach does not require computation of blockages caused by the flow boundaries, it is easy to use in practice. This theory can also be applied to the intakes located in general geometrical and flow conditions [for both two-layer-stratified flows and single layer flows (without stratification)]. Theoretical results obtained from this study match very well with the available experimental data.