APPLICATION OF MODIFIED DEPTH-AVERAGED NUMERICAL MODELS TO 2D MIXING SHAER LAYERS IN OPEN CHANNEL FLOW

Abstract

The clarification of 2D plane mixing shear layer in an open channel flow is important for various engineering field. The flow in a mixing shear layer is characterized by vortex formations due to the K-H instabilities. Therefore, it is necessary to predict precisely not only the time-mean flow patterns but also the turbulent features, such as turbulent intensities and Reynolds stresses for quantitative prediction of mass transport around a mixing layer. In previous many works, 3D computational methods with refined turbulence models have been developed mainly in mechanical engineering field. In shallow open channels, since the dominant flow pattern has basically plane 2D structure, the plane 2D depth-averaged model is applicable to some extent. In this paper, the depth-averaged 2D open channel equations with refined expression for Reynolds stresses are applied to the plane shallow mixing layer. The computations are performed under the conditions of the laboratory tests by Chu & Babarutsi (1988) and the applicability of the model is examined through the comparison between numerical and experimental results. The numerical results indicate that the present refined model can capture the fundamental aspects of flow phenomena.