Experimental Study On Hydrodynamic Characteristics Of Jet Impingement With Sediment-laden Flow

Up until now,a series of theoretical and experimental studies on jet impingement have been deeply and completely studied by former scholars.These studies mainly concentrated on clear water,but seldom on sediment-laden flow.However,there are many sediment-laden rivers in China,which are widely distributed.Especially in the northwest and North China,the sediment content of rivers is very high.Therefore,it is of great significance to study the jet impingement test of sediment-laden flow.On the basis of previous studies,the hydrodynamic characteristics of jet impingement of clear and sediment-laden water are systematically compared in this paper.The characteristics of impact pressure and fluctuating pressure are measured and analyzed by controlling the velocity of jet,the depth of water cushion in the flume and the sediment content of water flow through a self-designed hydraulic model.And the following main results and conclusions are listed as following:(1)The impact pressure along the bottom of flume of sediment-laden water is similar to the law of clear water.It reaches its maximum at the impact point and decreases along both sides of the impact point.With the deepening of the water cushion,the impact pressure tends to decrease at the impact point.However,the deeper the water cushion is,the greater the impact pressure is between 0.1 to 0.2m downstream of the impact point.The impact pressure increases obviously with the increasing of jet velocity.(2)The relationship between impact pressure and water cushion depth is deduced by Buckingham theorem under clear water and sediment conditions.The change rate of jet energy to impact pressure energy of sediment-laden flow is greater than that of clear water.The relationship between the jet impact width and the depth of the water cushion is obtained by studying the impact range of the clear water.(3)The distribution law of the pulsating pressure along the bottom of flume under clear and sediment-laden conditions are similar,and they are both similar to the distribution law of impact pressure.Under the experimental conditions of this paper,the pulsating pressure at the impact point increases with the increase of sediment concentration.The ratio of fluctuating pressure to impact pressure of sediment-laden flow at impact point is larger than that of clear water,and increases with the increase of water cushion depth.On the contrary,the ratio of fluctuating pressure to impact pressure decreases with the increase of water cushion depth.(4)The probability density distribution of fluctuating pressure under clear water and sediment-laden conditions are similar.And it obeys the standard normal distribution under different flow conditions for each measure points,while the deviation from the standard normal distribution at the impact point is larger than others.Meanwhile,the variation of sediment concentration has little effect on the probability density distribution of fluctuating pressure.(5)The power spectral density distribution of sediment-laden flow is similar to that of clear water,and the variation of sediment concentration has no obvious effect on the power spectral density distribution.As a whole,each measuring point is relatively distributed in the low frequency band and attenuates to zero within 20 Hz.However,compared with others,the power spectrum distribution at the impact point is concentrated in a lower frequency range.