Research On Rectification Measures For Forebay Of Side-inlet Pumping Station Based On Response Surface Method

For the forebay of a side-inlet pumping station,due to the flow enters from one side obliquely,it is easy to form a large-scale swirling area in the forebay,especially for the sediment laden flow,sediment deposition will occur in the long run,and the sediment deposition will further aggravate the main stream deflection.In front of the station,the phenomenon of water flowing into the pump sump is obvious,and the water flow deflection will seriously interfere with the normal operation of the side units and reduce the efficiency of the pump.Therefore,it is necessary to take rectification measures to improve the inflow flow pattern of the pumping station.By selecting appropriate rectification measures,the positive inflow condition can be created.At the same time,the bad flow patterns in the forebay can be basically eliminated,thus,the water flow can be ensured to enter the pump sump evenly and smoothly,and the safe and efficient operation of the unit can be ensured.the response surface methodology combined with numerical simulation method is used to optimize the different parameter combinations of the rectification measures,and the obtained law can be used as a reference for the setting scheme of the rectification measures in the forebay of the side-inlet pumping station.A 1:25 model of the forebay of the side-inlet pumping station is established,and the flow field of the original scheme is calculated under the designed water level.By comparing the flow pattern of numerical simulation with that of physical model test,it is proved that the numerical simulation results are reliable.Through the analysis of the numerical simulation results,it is found that in the original scheme,there is a large eddy in the forebay,the vortex center is located on the left side in front of the station,and there is also a large range of vortex in the intake channel,and the flow deflection is serious.The velocity distribution nephogram of the characteristic section in front of the station shows that the high-speed flow area is located on the right side of the station,and the velocity uniformity and weighted average angle of the section are relatively small.To improve the flow pattern of forebay,diversion piers,bottom sill and diversion wall are setted,with a total of eight rectification schemes.According to the analysis of streamline map of bottom layer and surface layer and axial velocity distribution cloud map of characteristic section,the rectification effect of bottom sill is the most obvious.According to the numerical analysis of the flow field evaluation index value,the bottom sill can effectively improve the value of velocity uniformity by 44.8%,while the "Y" shaped diversion pier can improve the weighted average angle by 3.6%.Through the single factor test,four parameters which have significant influence on the forebay flow field are selected,which are sill height,diversion pier angle,diversion pier length and diversion pier angle.The objective function Y value is constructed according to the ratio of velocity uniformity and weighted average angle of 4:6.Among the four factors,the influence of diversion pier angle on Y value is small.According to the prediction of the first response surface test,the numerical simulation of the optimal parameter shows that the actual velocity uniformity is 61.3%higher than the original scheme,the weighted average angle value is 9.4%higher than the original scheme,and the Y value is 25.5%higher than the original scheme.According to the prediction of the second response surface test,the simulation results show that the velocity uniformity,the weighted average angle and the Y value are improved by 73.3%,9.4%and 29.2%respectively.This method can be used for multi factor and multi-objective optimization of forebay rectification measures in the future.