Study On Characteristics Of Aerated Flow Over Spillway Chute With An Anti-arc Section

In the building of the high head, high-speed flow caused by cavitation erosion cavitation damage a direct impact on the quality and safety of the project, cavitation damage greatly restricted the development of the high head and discharge structures. Complex boundary conditions cavitation damage caused widespread concern in water conservancy workers at home and abroad. Aerated flow is one of the effective measures to reduce cavitation damage, when the water reaches a certain air concentration can effectively reduce or even eliminate cavitation damage, and the flow of air concentration and aerator size, the aerator flow regime, the feed rate and other factors are closely related, therefore, the study of anti-arc aerated flow characteristics it is very necessary. It is important to the depth study of aeration to prevent cavitation mechanism, and provide a theoretical basis for the design of high head and discharge structures.In this paper, through the model test and numerical simulation methods to study the characteristics of the anti-arc aerated flow, and to explore the aerator, anti-arc radius, the gas flow and other factors on the air concentration, and results of numerical simulation and model test results were analyzed, to verify the feasibility and accuracy of the numerical simulation method.Model test use3kinds of the ramp height,3anti-arc radius,6level flow, amount54kinds of working conditions; numerical simulation use two-dimensional mathematical model, calculated use the water-gas two-phase flow VOF model and RNG turbulent flow model, calculated with the same model test conditions.In different conditions water flow aeration effect good and play a good protective effect of anti-arc, downstream straight section of the chute can also play a protective role. The results of this study are as follows:Air concentration along the first increases and then decreases; different locations of the cross-section of the law also varies, cavity of the upper section of the surface of the water flow underside air concentration is larger, the middle of the water is small; after each section of the cavity air concentration show on the next big small law. Air concentration and the relationship of each factor is:When the ramp height and the anti-arc radius is constant, air concentration decreases with the increase in flow, the flow greater the smaller the air concentration; when the flow and the anti-arc radius is constant, air concentration with the aerator height increases; when the ramp height and the flow is constant, air concentration with anti-arc radius increases.Aerated flow velocity distribution law is:the along flow rate gradually increases, upstream straight rapid growth due to the steep flow velocity, anti-arc and downstream straight off the flute gradient of the flow rate of growth relative to the slow growth of the upstream flow velocity; flow rate of each section showing the middle on both sides of the law of small, the flow rate is smaller due to the bottom of the water and the water surface by the chute bottom slab and the effect of air resistance, the middle of the water from outside influence smaller flow rate greater.When other conditions remain unchanged, the length of the air with ramp height increases, aerator greater height, higher the height of the water jets, Water has greater potential energy converted to kinetic energy greater, flow projectile farther, the cavity length is greater.Comparative analysis with the results of numerical simulation and model test results, come to the results of numerical simulation and model test results consistent, with high accuracy. Therefore, aerated flow simulation using numerical simulation method is feasible.