Model Test Of Fluctuating Pressure And Uplifting Force Of Hyper-concentration Flow On Slabs

Up until now,the hydraulic characteristics of in energy-dissipating structures have been extensively studied,but mainly concentrated in the scope of flow contains no sediment.And relatively little research has been done on the effects of high-sand flow currents on hydrodynamic characteristics.However,when the flow carries sandy,the hydrodynamic pressure and stability of energy dissipation buildings will be different.so it is necessary to carry out research on the hydrodynamic characteristics with hyper-concentrated flow.In this paper,the influence of the sediment concentration of jet on the pulsating pressure in the plunge pool and the lifting force of the bottom plate is measured and analyzed by using hydraulic model test and changing variables such as sand concentration,jet velocity,and water depth.The main conclusions are as follows:(1)Under different sediment concentration and inflow conditions,the distribution trend of the time-averaged pressure and pulsating pressure of the gap between the plunge pool bottoms are similar along the direction of the flow,reaching a maximum near the impact point and gradually decreasing both sides.For the same measuring point,the time-averaged pressure increases with the increase of sediment concentration.The variation of pulsating pressure with the sediment concentration is closely related to the water flow condition.When the water flow condition is weak,the pulsating pressure of the sandy water flow is stronger than the clean water,and when the water flow condition is strong,the pulsating pressure of the sandy water flow is smaller than the clean water.(2)For different conditions of sediment concentration,the distribution rules along the path of the time-average value of the lifting force and the maximum lifting force on the bottom plate are similar,reaching a negative peak at the impact point and increasing rapidly in the upstream and downstream sides.The standard deviation of the lifting force takes the maximum value near the impact point,and then the lifting force drops rapidly from the maximum point to the sides.With the increase of sediment concentration,the mean value of the upward force received by each plate in the plunge pool increased to varying degrees.The standard deviation of the lift force is closely related to the hydraulic conditions with the variation of sediment concentration,and may increase or decrease with the increase of sediment concentration.(3)Regardless of whether the water flow contains sand,the pulsating pressure between the gaps of the bottom plate and the probability density distribution of the lifting force on the bottom plate basically obey the normal distribution,and the sediment concentration condition has little effect on the probability density distribution of the pulsating pressure of the water flow.(4)The pulsating pressure under the sandy water flow and the power spectrum of the pulsating power of the bottom plate are similar to those under the clear water condition,and the dominant frequencies are all in the low frequency range,but the frequency bandwidth of the pulsating energy of hyper-concentration flow is larger than that of the clean water.(5)The time integral scale of the pulsating pressure near the point of impact stagnation decreases with the increase of sediment concentration.For the area farther from the stagnation point,as the sediment concentration increases,the integral scale of pulse pressure decreases first and then gradually increases.