Effect of Secondary Current on Flow Prediction in an Open Channel Flow

Abstract

The present thesis is an outcome of physical and numerical research of secondary current effects in open channel flows with both smooth and rough configuration in prismatic cross-sections. Experiments have been conducted for open channel flows of rectangular and trapezoidal cross-section with four different roughnesses to develop models and also to find calibrating coefficients. Using micro-ADV we have been collected 3-D data sets and evaluated Reynolds stress and calibrating coefficients (i.e. secondary flow parameter Γ, eddy viscosity coefficient, friction factors f ). These coefficients play an important role in prediction of depth averaged velocity and boundary shear stress of an open channel flows. These are found to vary with flow depth, geometry, roughness and hydraulic conditions. A mathematical expressions have been formulated to predict these variables in terms of non-dimensional geometry and hydraulic parameters such as aspect ratio, lateral distances along width of the channel and vertical distances above bed are, and respectively. The new expressions are expected to improve the Shiono and Knight method (SKM) and accurately predict depth averaged velocity distribution in an open channel flows for different geometry, surface and flow conditions. The predictions of depth averaged velocity using new expressions obtained from multi-linear regression were found to provide better results as compared to SKM. The prediction capability of model has been also well validated against experimental data sets, FCF data series and natural river data series.