掺气坎后射流空腔积水的二维紊流数值模拟

Numerical simulation on 2-D turbulent flow of backwater in cavity of jet flow from chute aerator

在不考虑掺气浓度分布情况下将掺气坎上的水流流动按水气分层两相流进行研究，采用VOF方法和k～ε紊流模型进行数值模拟，得出了不同类型坎下积水情况和水舌形态。研究认为，掺气坎体型尺寸及下泄流量不变时，掺气空腔内积水程度随泄槽底坡加大而减弱直至消失；掺气坎体型不变，佛氏数的变化仅随流速变化时，佛氏数增大则积水程度减弱直至消失。对某大型水利工程放空洞掺气挑坎的数值计算结果与试验结果吻合较好，表明将紊流数学模型用于掺气坎后射流空腔积水的数值模拟是合理可行的。

Without considering distribution of the aerated concentration, the flow over the chute aerator is studied herein as an air-water two-phase stratified flow; in which a numerical simulation is made with both the VOF method and the k -ε turbulence model, and then the conditions of the backwater and the patterns of the nappe under various aerators are obtained. The study considers that the backwater in the aerated cavity is to be taken off and then disappears along with the enlargement of the bottom slope of the chute, when the shape size of the aerator and the flow rate of the discharge are unchanged ; while the shape of the a- erator is unchanged and the Froud number is only changed along with the flow velocity, the backwater is to be taken off and then disappears by following the increase of the Froud number. The result from a numerical calculation made for the aerator of the emptying tunnel of a large water control project shows a better coincidence with that from the test. Therefore, it is demonstrated that it is reasonable and feasible to apply the mathematical model of turbulent flow to the numerical simulation on the backwater in the cavity of jet flow from chute aerator.