Author(s): M. R. Kavianpour; Saber Moazami
Linked Author(s):
Keywords: Numerical modeling; Two Phase flow; Air-water mixture; Air concentration
Abstract: Two phase flow is a common phenomenon, occurring in many situations of hydraulics engineering such as, stepped and storm waterways, reservoir outlets and in water treatment plants. In outlet conduits and tunnel spillways, high velocity flows, pressure reduction and intense pressure fluctuations due to flow separation provide situations favorable for cavitation erosion. It has been found that flow aeration in such situations and especially downstream of outlet gates will eliminate cavitation tendency and its damages. In this paper numerical analysis of two phase air-water flow in bottom outlet conduits is presented to determine the flow characteristics and the quantity of air demand downstream of outlet gates for different gate openings and heads of water. Also numerical results of pressure distribution and cavitation index, the variation of air concentration along the tunnel and near to the bed are presented. Therefore, the numerical results of the model within the outlet conduit were provided for two conditions of with and without air injection. Due to high Reynolds number, standard two equation k-ε turbulence model was used for the simulation of air water mixture. For long tunnels, it would help to determine the position of successive aerators, if required. The model is calibrated with backward-facing step and the results are also compared with available experimental information.
Year: 2007