Efficiency of Air-Entraining Vortex Formation at Water Intake

The basic mechanisms for air-entraining vortices to form at a water intake are examined and vorticity arising in boundary layers is considered in detail. Theoretical expressions are developed for calculating the maximum strength of air-entraining vortex which may form at a water intake. Experiments confirm that it is possible to calculate the strength of vortex from a knowledge of approach conditions and intake geometry. For the conditions of these tests the efficiency of vortex formation is approximately unity. A kinetic energy evaluation for the approach flow and intake flow sections indicates the organizational nature of the process and gives values for the additional pressure losses at an intake which are attributable to vortex formation.