Numerically Modeling Flow Rates and Pressures Over a Variety of Dam Shapes

Abstract Only - As improved data collection and hydrologic information becomes available to calculate flood flows, it is possible that a dam could be under-designed if the design flood is increased. In such situations, it is important to accurately predict the discharge coefficient of the dam, thereby allowing a correct discharge rating curve to be generated. In addition, an increase in the design flow will affect the pressures on the dam spillway. Past studies have shown that non-typical dams that vary from the standard design may have significant differences in the discharge coefficients and pressures from design nomographs. In the past, to calculate the discharge and pressure parameters for a specific dam crest, model studies have been used. With the advances in computing power and numerical algorithms, Computational Fluid Dynamics (CFO) has added another tool in the hydraulic analysis of dam spillways. This study compares the numerically computed discharge and pressures with the results from sectional physical models. The crest shapes include ogee crests, trapezoidal shaped crests, and a non-typical ogee type crest. For two of the ogee-crest spillways, pressures are compared for submergence on the downstream spillway. The results show that discharges can be predicted within a± 4% window. Pressures are generally in good agreement as well. The numerical results for a slightly non-typical ogee crest compared more favorably with the model data than values taken from the typical USAGE or USBR design graphs.