Post-Processing of Air Entrainment on NASIR Flow Solver Results for Skimming Flow over Stepped Chutes

摘要

Air entrainment plays an important role in the reduction of cavitations risk potential in chutes and spillways. The advantages of stepped spillways over conventional smooth spillways, the air entrainment phenomenon, and the flow regimes occurring on stepped chutes have been reviewed. Then the numerical analysis of skimming flow using shallow water equations in inclined coordinate system is described. The numerical computations of air entrainment in the skimming flow over stepped spillways are performed in two stages. In the first stage, the water flow equations are converted to discrete form using the overlapping cell vertex finite volume method on triangular unstructured mesh, and then, in the second stage, the flow field solution results are used for computing air concentration profiles by a separate post-processor. This postprocessor uses experimental relations for computing the inception point characteristics and air concentration distribution profiles along the stepped chute. The computed results of air entrainment into the supercritical skimming flow on stepped spillways have been compared with laboratory experimental measurements.