Experimental Research on the Flow Deflection Features Downstream of a Sluice with Large Expansion Ratios.

Deflected flow, as one of undesirable flow patterns, may scour river beds and banks seriously. Experiments are conducted at a symmetric multi-gate sluice model with different large expansion ratios and Froude numbers. The LSPIV (Large-Scale Particle Image Velo- cimetry) technique is adopted to collect the velocity data of free surface downstream. This study aims at the flow deflection features on the condition of symmetric inflow and outflow. The results show that the velocity distribution at the cross sections display an S shape. The flow dynamic axis is deflected obviously. It is classified into three reaches according to the differences of the dominant factors on the whole deflected flow zone. In general, as Froude number increases, the reach dominated by the total outflow width tends to shrink, while the reach influenced by the enlarged boundary width downstream tends to expand. The deflected ratio of flow is a function of Froude number and expansion ratio by the method of regression analysis, and the deflected ratio increases with Froude number and expansion ratio within limits. The maximum of deflected angle is less than20°. These achievements are instructive to putting forward the improvement measures of undesirable flow patterns. [ABSTRACT FROM AUTHOR]