The Bottom Of The Ming Trough Anti Arcs Aerator Experimental Study Of The Flow Characteristics

In the hydraulic projects, the body type of discharge structure is often more complex. Except for the straight-line slope segment, the chute slope will also come across a large number of curve segments such as anti-arc discharge. In the present study the mechanism of anti-arc cavitation, or the optimization of the anti-arc curve, or the shape optimization of the aerator, the aims are relief cavitation damage using of aerated water. Aeration must make the water reaches a certain air concentration, the air concentration of flow and over-current boundary conditions is closely related, such as the flow pattern aerator, aeration cavity properties, into the air and other factors. Therefore, it is very important that the complex of anti-arc boundary condition aerator flow characteristics and its influencing factors. This is complicated further in-depth understanding of the kinds of boundary conditions the mechanism of aeration and rules of the design for the dam project to provide a more reliable theoretical basis for the aeration expand new areas of research.In this paper, the experiments on the hydraulic model of open channel with anti-arc have been carried out, and study anti-arc radius, aerator type and size of the water falling on the anti-arc Aeration effect, and impact analysis and discussion the factors of the cavity length and the depth of cavity backwater. In the experiments, there are nine aerators, three anti-arc radius and eight flows.The cavity length is the most important indicator to test the effect of aeration. The results show that the cavity length increases with the increasing of flow, anti-arc radius, bucket height and slope, when the tank bottom slope remain unchangeable; when the bucket reaches a certain value slope, the cavity length will not increase but will decrease. For the same anti-arc radius, bucket height or slope bucket, with the Froude number increases, the cavity length change is not one-way, showing "S" to the change of characteristics.Using the differential equation of the aerator jet, the pressure of cavity of aerator at the bottom of anti-arc are calculated in open channel with model test results. Analyzing the impact of flow, anti-arc radius and other factors on cavity aeration pressure, and revealing the basic law:the cavity aeration pressure increases with the reduction of flow in anti-arc complex boundary conditions, and when the flow is lower than a certain critical value, the cavity aeration negative pressure disappeared; and it increases with the increase of anti-arc radius, but the anti-arc radius increases to a certain extent, its impact on the cavity pressure will weaken. To ensure adequate length of cavity aeration and maintain a good vacuum, in order to facilitate fully water aerated, get a good aeration effects, it need to have moderate anti-arc radius.The cavity backwater not only affects the water aerated, but also to the stability of cavity. The results showed that the smaller of anti-arc radius, the greater of impact angle of water tongue, the more obvious of the effect on the cavity backwater; With the flow, bucket height and slope increases, the depth of cavity backwater increases, when the bucket reaches a certain slope, the depth of cavity backwater will not increase; As the Fr increases, the depth of cavity backwater's change is not one-way.Analysis the effect of air vent on the cavity length. The results show that the effect of air vent area on the length of cavity is obvious. The bigger area of air vent, the longer of the length of cavity when the other hydraulic factors remain unchangeable. But when the areas of the air vent reach some value, the length of the cavity no longer increases with the increase of the air vent area. Therefore in the project, the proper air vent area is important for designing an aerator.