Design optimization of submerged vane system for sediment control.

摘要

The purpose of this study is to refine the design of submerged vane systems. Submerged vanes are small flow-training structures installed on the streambed to redistribute local flow and sediment transport. By generating secondary circulation in the flow that alters magnitude and direction of the bed shear stresses, a vane system can cause a local change in the distributions of velocity, depth and sediment transport in the area affected by the vanes, which provides a means for sediment control in alluvial rivers. The technique has been used successfully in field applications. The goal of this study is to use advanced optimization technique to refine the design and improve its efficiency.; To formulate the optimization problem, the study first derives the objective function. As the efficiency of a vane increases when its lift increases and its drag decreases, an appropriate design function is one that includes the ratio of lift and drag. Two vane geometry construction methods are defined to represent the vane shape mathematically. One is a NACA four-digit vane, one of the NACA airfoil family; the other is a Bezier-spline vane that has the advantage of facilitating more complex vane geometry and possibly even better vane shape. The constraints associated with these two types of vanes are defined by examining the range of each parameter controlling the vane shape.; Due to the non-continuous nature of the problem, optimization procedure based on a Genetic Algorithm is developed and applied in the design of a single vane. The optimal angles of orientation and twist are determined by searching for the highest lift while changing the angle of attack at tip and root section of the vane. The optimal system layout (i.e. lateral and longitudinal vane spacing) is obtained by examining the vane-induced flow field downstream of the system.; The final system designs show significant improvement in performance compared to the previous designs. The new designs not only reduce constructing cost but also reduce the vane-induced channel resistance. As a result, the new designs are both technically efficient and economic.