Numerical Simulation And Angle Optimization Of Flow Field In Forebay Of Pumping Station With Diffusion Angle

Pumping station is an important water conservancy project in China and its safe and stable operation is crucial in the development of our country.The forebay of pumping station is one of the keys to the safe and stable operation of pumping station.A reasonable forebay of pumping station can not only make the inflow of pumping station smoother and improve the operation efficiency of pump,but also reduce the cost and save the cost.In this paper,the six-hole inflow pumping station was taken as the research object and the flow pattern of the forebay of the pumping station under various diffusion angle schemes was analyzed by numerical simulation,then the dynamic influence mechanism of the diffusion angle and its flow pattern change of the forebay of the pumping station was explored.By further considering the economic analysis and combining the information weight method and the regression analysis method,the value range of the diffusion angle optimized by the applicability optimization and accuracy was obtained.Finally,the accuracy and reliability of the numerical simulation results and the optimized diffusion angle range were verified by the physical model test and a more accurate diffusion angle selection interval suitable for the design of the forebay of the pumping station was proposed.Finally,the following conclusions are obtained:(1)When studying the flow pattern of the forebay with different diffusion angles,it can be found that with the increase of the diffusion angle,the uniformity of the velocity in the forebay continues to decrease,the vortex area continues to increase and the change rate shows a phenomenon of first slowing down,then relatively stable and finally accelerating.When the diffusion angle was less than 26°,with the increase of the diffusion angle,the range of the low-speed vortex area on both sides of the forebay became larger,the uniformity of the velocity became smaller,while the change rate of the two gradually slowed down,the range of low-speed vortex and the alteration rate of velocity uniformity on both sides of the forebay kept relatively slow and stable growth between 26° and 38°.When the diffusion angle was greater than 38°,the alteration rate of the low-speed vortex area and the velocity uniformity on both sides of the forebay began to accelerate.Therefore,during the range of the alteration of the flow pattern in the forebay,the upper limit of the optimal diffusion angle selection range should be set between 26° and 38°.(2)The influence of the alteration of the diffusion angle on the flow pattern and the inflow condition of the inlet channel was different.According to the change of each index,the flow of the 1#and 6#inlet channels near the side wall was the most affected by the change of the diffusion angle,followed by the 2#and 5#inlet channels,which are slightly less affected than the 1#and 6#inlet channels.The 3#and 4#inlet channels were the least affected by the diffusion angle which can maintain good inflow conditions throughout.(3)The flow pattern in the inlet channel will deteriorate with the increase of diffusion angle.From the angle of the index of flow deflection,the increase of diffusion angle will increase the angle of flow deflection in the inlet channel and the rate of increase will decrease first and then increase,the growth rate of flow deflection reaching the lowest value at 26°.From the index of velocity uniformity,the increase of diffusion angle will reduce the velocity uniformity of water flow in the inlet channel and the rate of decrease will slow down first and then increase reaching the lowest value at 34°.The relationship between the amount of concrete and the diffusion angle of the forebay project is a trigonometric function,to be specific,the amount of concrete will first decrease linearly and then tend to be horizontal with the increase of the diffusion angle.The alteration rate was in a relatively slow state at 20° diffusion angle and basically tended to be horizontal at 22°.(4)Through the physical model test,the optimized diffusion angle range verified,it can be seen that when the diffusion angle is 38°,the overall flow pattern of the forebay and the inlet channel was poor and it was not suitable as the selection angle of the diffusion angle of the forebay.Although the overall flow pattern of the 34° diffusion angle forebay and the inlet passage was slightly lower than that of the 26° diffusion angle forebay,the difference was not large and can better meet the inflow conditions of the pumping station.Finally,combined with the numerical simulation results and the physical model verification results,the optimized diffusion angle range of the forebay was 20°～34°.In order to facilitate the practical engineering design and application,combined with the research content of this paper,a more accurate diffusion angle selection range of 20°～35° was proposed for the design of the forebay of the pumping station.In this paper,combined with mathematical model calculation and physical model verification,the information weight method and regression analysis method were adopted to explore the variation law of the flow pattern of forebay and the inlet channel with the alteration of the diffusion angle.It was proposed that the more accurate diffusion angle selection interval suitable for the design of the forebay of the pumping station was 20°～35°,which provides a more accurate and reliable range for the selection of the diffusion angle of the forebay in the design of the pumping station,along with some reference for the study of the diffusion angle of other forebays.