| Combining with the design requirements of the Huangchigou water distribution hub for the side channel spillway of the water distribution pool,the hydraulic characteristics of the side channel spillway have been studied by using hydraulic model tests.Measured hydraulic parameters of the spillway including flow velocity,pressure,surface profile,etc.The flow pattern,conveyance capacity,aerated water depth of the spillway,and the flow cavitation of the steep slope have been evaluated and analyzed.Furthermore,in order to explore the optimal combination of the bend and steep slope of the side channel spillway,the numerical simulation of the spillway is carried out based on the orthogonal experiment.The main results are as follows:(1)Under each design flow rate of the side channel spillway,the corresponding test pool water level is lower than the design.When the water level of the dividing pool is controlled at the design,the corresponding test discharge flow is greater than the design.It shows that the side channel spillway meets the requirements of the conveyance capacity.When the overflow of the side channel spillway is 47m3/s,the flow coefficient of the side weir is 0.516,and the overflow is 70m3/s,the flow coefficient of the side weir is 0.405.Under this flow,the top elevation of the right bank revetment of the section 3#and 4#of the apron is insufficient.It is recommended to increase the height of the bank revetment side wall appropriately.(2)In the test,the water level of the pool was not higher than 516.20m under all working conditions,and the top elevation of the Qinling tunnel is 516.76m,so the Qinling tunnel doesn't appear a transient mixed free-surface-pressure flow.When the flow rate is large,the flow pattern of the stilling pool is poor,which cannot meet the requirements of the hydraulic jump energy dissipation.Through simple model test of the modification scheme of the stilling pool,three relatively ideal schemes of flow pattern of the stilling pool are recommended,which adopted by engineering should be determined through further model test.(3)The measured minimum pressure of weir surface(0+000.00?0+000.70)is negative when the discharge is 56m3/s,which is-0.21×81kpa,and the pressure of other parts is positive.The fluctuation pressure of the steep slope is the smallest,the side channel is the second,the stilling pool is relatively large,whose dominant frequency is small,and its value is less than 1Hz,which is a low-frequency range.It shows that the overall pressure distribution of the side channel spillway is reasonable,which won't affect its safety.(4)The highest water surface elevation after aeration in each section of the side channel spillway is lower than the design wall top elevation,while the maximum aerated water depth of the stilling pool is 5.39m,its design side wall height is 6m,the section clearance is about 10.17%,which is less than 15%?25%.It shows that the clearance area of the stilling pool doesn's meet the design requirements,and its section size needs to be increased appropriately.(5)The cavitation number of the steep slope gradually decreases along the way,whose minimum value appears at the end of the steep slope,which is 1.07.The cavitation numbers of the other sections are large,and the maximum flow velocity is about 14.55m/s at the end of the steep slope,which is less than 15m/s,It shows that the steep slope is less likely to be damaged by cavitation water.(6)The applicability of the numerical model is verified by the hydraulic parameters obtained from the experiment.Under the condition of changing the longitudinal gradient,width and curvature radius of the bend at the same time and taking three levels respectively,the numerical simulation of the spillway is carried out based on the orthogonal experiment.Through the comprehensive analysis of range variance,it is found that the optimal scheme is that 0 longitudinal gradient,4.4m width and 22m curvature radius of bend.It can effectively reduce the transverse water surface difference in the bend,and improve the flow of the bend and downstream,which has a positive impact on the stable operation of the spillway and the erosion of the downstream. |
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