Study On Characteristics Of Aerated Flow Over Spillway Chute With Deflecting Flow

Among the numerous hydraulics problems caused by the high speed water, the cavitation and its damage of the release structures is special prominent. By setting aerator facilities on the surface of the outlet structures to reduce or avoid the cavitation damages has became a most effective measures to alleviate cavitation. A successful aeration facility not only can make the water intake enough air quantity,but also can make the near wall keep a certain air concentration in a long range. While the air concentration of flow has a close relationship with many factors, such as the over-current boundary conditions, the flow pattern aerator, aeration cavity characteristics, air inflow and so on. So it is very important to study the characteristics of aerated flow and its impact factor with the complex boundary.The article is aimed to study the characteristics of aerated flow of the chute with deflecting flow through the hydraulic model. According to the change of conditions, including the aerator type, the anti-arc radius, the flow and so on, research the influence on the effect of the aeration, and analyse the factors which affect the air concentration distribution and the length of cavity. By establishing a two dimensional mathematical model for numerical simulation and using two-phase flow VOF model and RNG turbulence model to simulate the flow regime of aeration, nappe shape, flow distribution, and the characteristics of aerated cavity in different conditions. Compare the results of numerical simulation with model experiments to check the feasibility and veracity of numerical simulation. The main work and achievement are concluded as following:In the experimental range, the air concentration distribution increased gradually at first, then declined gradually and close to a stable value. To the vertical distribution of air concentration, the upper aerated flow concentration distribution in the cavity firstly decreased,then gradually increased; the downstream of the cavity, aerated flow from the floor to the surface direction, the air concentration distribution increased gradually, and the closer the surface of the water, the faster increase in air concentration. Aerated flow velocity distribution along gradually increased, from the floor to the surface direction of water flow velocity distribution gradually increased at first and then gradually reduced.When the anti-arc radius, the gas flow is constant, with the air ramp height increases, the cross-section of different water depths of air concentration value also increases. When the ramp height, the gas flow is constant, with the anti-arc radius increases, anti-arc cross-section of different water depths of air concentration value also increases. When the ramp height, the anti-arc radius is constant, with the flow increases, each section of different water depths of air concentration value will decrease.In the experimental range, when the flow is constant, with the ramp height increase, the cavity length also increases. When the ramp height is constant, with the flow increases, the cavity length will decrease.According to numerical simulation, different working conditions water can form a stable cavity after aerator, the water flow in the tank stream-state is smooth, and the surface of the water fluctuations is smooth. Aerated flow velocity distribution along gradually decreases, reaching the lowest point of the pick stream segment maximum velocity. When the anti-arc radius, the flow is constant, with the ramp height increases, the cavity length and height also increases.By comparing the results of the experimental model test results and numerical simulation, both derived from the flow pattern is consistent. The water tongue shape of the numerical simulation and model test results are in good agreement, local deviation. To the aerated cavity length, the results of numerical simulation are larger, but the cavity length with the bucket with the increase of this law is consistent with the model test results.