The Experimental Study On Velocity Distribution Regulation And Hydraulic Characteristics About U-shaped Channel

The rivers, channels, as well as in hydraulic tunnel with free surface flow are referred to as open channel flow, uniform flow in open channel is the most fundamental problems in open channel hydraulic calculation. In irrigation canal system, U-shaped channel is widely used in production practice, on account of the advantages as large flow capacity, remarkable anti-seepage effect, sediment transport capacity, superior forceresistance, less occupied area and so on. Because of the specificity of its shape, complex flow condition, and widely used in the short time, study of U-type hydraulic characteristics of channels are not perfect.Based on the U-shaped channel in a uniform flow conditions were investigated, thepaper point at the studies of three kinds of different geometrical size U-shaped channel, theflow, water depth, bottom slope hydraulic factors as the main variables, to test the differentflow conditions channel flow, analysis of the sectional velocity distribution of the channel,turbulence characteristics, methods of inquiry channel flow calculations. The main resultswere as follows:1. According to the analysis of measured velocity on contour map, the perpendicularbisector as the center in channel, velocity on both sides is symmetrical basiclly,midperpendicular velocity is largest; location of the maximum velocity is below the surface,the maximum velocity of the vertical position in the range of0.6～0.8y/h, bottom slopechange had no effect.2. Through the discussion on the comparison of different vertical distribution formulaand the test data to flow rate, that the actual distribution of parabola form and doublepower-law form can reflect the flow rate, the two comparison, The relative error of doublepower law formula calculation result is smaller than that of parabola formula calculation,therefore, the double power law formula can expresses the vertical flow velocitydistribution law. 3. On the basis of international scholars studies about lateral velocity distribution,used the exponential form showing the lateral velocity distribution, the distribution oftransverse flow form, through a large number of experimental data fitting velocitydistribution formula, lateral velocity distribution formula was established.4. The calculation formula of cross section flow was putted forward,on the basis of theestablishing of the sectional velocity distribution formula in U-shaped channel. Theprecision of example calculation conformed to the engineering requirements. As well as, thebuoy experiment was used on channels, and buoy coefficient are given. Buoy methodcould be used for U-shaped channel flow measurement being proved.5. The fluctuation process line of different measuring points was analyzed, the were the basic similar, and had different quasi periodic. Consistent probability distribution calculated by the velocity probability distribution statistics of measured data and thetheory of normal distribution, three-way fluctuating velocity can be considered to fit the normal distribution.6. The turbulence intensity of every vertical lines in longitudinal direction and verticaldirection from the canal bottom to the surface of the water decreased first and then increases,the longitudinal turbulence intensity was maximum, minimum turbulence intensity did notappear on the surface of the water, but some distance below the free surface. The changerule of vertical turbulence intensity was similar with the longitudinal turbulence intensity,transverse turbulence intensity changed in a small range, water momentum exchange wasmore stable, longitudinal and transverse relative turbulence intensity is close to a constantvalue.7. The change of vertical Reynolds shear stress is relatively uniform with the waterdepth, and approximate to a constant value, small range ability in the axis on both sides. Inthe range of y/h>0.5, vertical and horizontal Reynolds shear stress was approximatelylinear, and in the range of y/h <0.5that was approximately triangular distribution.Transverse Reynolds normal stress distribution along the depth was relatively uniform,approximately linear changes, and in different survey line on the same transverse, Reynoldsnormal stress values are relatively close.