Gas Experimental Study And Numerical Simulation Of The Bottom Of The Chute Mixed

For meeting the urgent requirements on power supply and water resources comprehensive utilization by national economic development, the construction of high dam engineering has been increasing more and more, while the cavitation erosion damage of outlet structure brought by has been increasingly prominently. Engineering practice proved that aeration for preventing cavitation erosion is an effective corrosion prevention technology with simple form and reliable operation. However, as it involves the two aspects of water and gas, its mechanism and process is still unclear. Combining with physical modeling experiment and numerical simulation computation, the exploratory study on the aerated concentration of indoor chute is carried out, which is conducive to further understanding the mechanism and rule of aeration for preventing cavitation erosion.The aeration facility layout shall be confirmed by model test combining with engineering practice, and75kinds of different working conditions shall be designed by utilizing single factor cyclic method. Under each working condition, the water depth, flow velocity, cavity length and aerated concentration shall be respectively measured, so as to analyze and discuss the contents including aerated water flow characteristics, aerated cavity characteristics, aerated concentration and aerated protection length.In the technical study on aeration for preventing cavitation erosion, cavity length is the most important aspect, which determines the effective corrosion prevention scope of aerated amount and aeration facilities. Experiment results show that:when aerator contour is confirmed, the flow rate and cavity length would be increased. However, when flow rate increases to certain degree, the increase of cavity length would be very little and tend to be at extreme value; when other conditions are constant, the higher the aerator height, the length of cavity would be bigger. However, aerator height also has certain limit scope, and too high would be likely to cause cavity water logging and influence aeration; under different flow rate or aerator height, cavity length would increase with the increase of air vent radius, but the amplification would slow down later. When the radius of air vent reaches certain dimension, the cavity length would not increase any more.The change condition of aerated concentration is the important judgment basis for confirming the effective protection length of aerated facilities. Respectively under different flow rate, different aerator height and different air vent radius, this paper carried out analysis on the change conditions along the aerated concentration at the near bottom side and the distribution condition of some measuring sections. It obtained that: the aerated concentration at the near bottom side nearby the drop point of jet flow is high, which almost reached extreme value. Then it decreased sharply along the course, and until certain distance, the attenuation rate of aerated concentration at the near bottom side was obviously slowed down; while the aerated concentration of measuring section mostly exhibited "S" type curve distribution along water depth direction. In view of the above, an empirical estimation method taking cavity length as the aerated protection length of dynamic measurement unit is put forward.Later on, Eulerian Model suitable for the flow of mixed phase was adopted to carry out three dimensional numerical simulation on chute aerated characteristics. The unstructured meshing computational domain was obtained by analog computation, and non-steady first order implicit iteration was applied to solve. The aerated state of flow, velocity distribution, cavity characteristics and aerated concentration distribution, etc under part of the working conditions were simulated. Moreover, through the comparison and analysis with experiment results, it was found that the simulation and experiment results matched well, and few had slight difference.