Shape Optimization of Spillways Design Using a Gradient Based Algorithm

Spillways are hydraulic structures that regulate flow control in dams in order to prevent their failure during floods. Weirs efficiency depends mainly on their crest shape. Currently, their geometry has only been studied empirically due to the complex flow nature. Hence, the aim of this study is to carry out a numerical optimization procedure of the spillway design. Advances in computational fluid dynamics (CFD) allow a better understanding of free surface flows. Code_Saturne, which is a CED model developed within EDF R&D incorporating a Volume Of Fluid (VOF) method, computes the weir upstream water level for a given flow discharge. Then, a shape optimization methodology was developed to maximize the flow discharge coefficient while at the same time taking into account the damage risk by cavitation of the weir. With the help of a 2D model, the head discharge was minimized while limiting negative pressure appearance along weir crest. The optimization study was based on a gradient descent algorithm and a Bezier curve parametrization of the weir shape. A comparison between the optimal shape hydraulic performances and the standard weir shape highlights a significant gain in the flow discharge of the structure.