The Experimental Study On The Hydraulic Characteristics And Measurement About U-Shaped Channel

The water flow of Natural River and irrigation canal system is turbulence which is a complicated flow phenomenon. A number of scholars have studied and explored the regular patterns and the hydraulic characteristics of turbulence via flume and field test. However, since the turbulence structure is complicated and cross section and roughness forms are changeful, the description of the flow, even the simple open-channel flow, is not satisfying. In the actual engineering, U-shaped canel cross section has been widely applied. The velocity distribution and turbulence characteristics of the U-shaped canal cross section are still in the stage of development and lots of fundamental research problems in the measure techniques of cross section still remain to be solved.In this paper, the U-shaped canal is chosen as the main object of study, aiming to make research on the velocity and buoy filling factor of U-shaped canal cross section and obtain the formula of distribution of the velocity of U-shaped canal cross section and formula of different buoy filling factors so as to find the flux formula of features of velocity distributions of U-shaped canal. Vectrino+ are adopted in the experiment to accurately observe the three dimensional velocity of measuring point in the flow, which accordingly leads to better analysis of the regular pattern of distribution of three dimensional turbulence characteristics of U-shaped canal. Conclusions below can be drawn through this research:1. The velocity distribution of each side of the perpendicular bisector is symmetry and parallel and the maximum velocity is below the free surface of the perpendicular bisector; the contour map of velocity close to side walls is similar to the outline of side walls; the position of point of maximum velocity is decreasing with the depth of water going deeper; since the maximum velocity of cross section is under the water surface, the velocity contour goes towards the center when it is getting close to the water surface. The change is more obvious if the water is deeper.2. There exists function relation between dimensionless relative velocity u/v and relative water depth and the main influential factors on coefficients-a, b, c and their corresponding functions are determined.3. The transverse velocity distribution accords with the exponential function distribution. the relation between the relative velocity v/vm and the relative position 2Z/B and the change range of coefficients m and n are determined. Through the data generalization analysis of transverse velocity distribution, the function of transverse correction coefficient kh between the average velocity of perpendicular bisector in the U-shaped canal and cross section can be obtained.4. The probability of three dimensional fluctuating velocity accords with the normal distribution pattern. The transverse velocity probability distribution is most concentrated wherever the measure position is. The probability distribution of frequency curve of three dimensional velocity in free turbulence area is relatively close while the deviation is bigger in the strong shear zone. From the surface to the bottom, the variation of longitudinal fluctuating velocity in the concentration area from the surface to the canal bottom is increasing prior to decreasing; the variation of transverse and vertical fluctuating velocity is invariant.5. The distribution of turbulence intensity alongside the vertical line is substantively in triangular shape with the maximum turbulence intensity decreasing at longitudinal and vertical direction near the free surface. The relative turbulence intensity is similar to the description of turbulence intensity with the relative longitudinal turbulence intensity around zero.6. The longitudinal and vertical reynolds shear stress y/h<0.5,reynolds shear stress is increasing suddenly. The transverse reynolds shear stress is linear. The shear velocity obtained by transverse reynolds shear stress is far different from the shear velocity obtained by the resistance balance of steady uniform flow.7. By analyzing different buoy filling factors, it is found that the virtual flow is increasing when the depth of the submergence of the buoy is increasing and the flow formula of floating measurement at different filling factors is given in the paper.