On the Distribution of Velocity in a V-Shaped Channel

Abstract. Several series of measurements were conducted to explore the hydraulic characteristics of a V-shaped bottom channel by using low & high-speed velocity propellers for point-wise velocity measurements. Also, in order to understand the e ect of cross sectional channel shape on the distribution of depth-averaged velocity in the experimental channel, cases with di erent ow rates were examined. Using SURFER software, the contour plots of 2D isovels were drawn as interpolation among averaged depths and velocities, obtained from superposing the various pro le sections. It was observed that isovels are parallel to the channel boundary in a region close to the bed, and almost symmetric about the centerline, with some deviations. The variation of point velocities in each slice considered along a spanwise direction, in order to study the depthwise velocity pro le distributions, is shown. The lateral variations of depthaveraged velocities indicate that the velocity distributions are almost symmetrical about the cross sectional centerline, except for some ow cases, in which there are slight deviations, despite the fact that the ow condition was uniform for all cases. It was found that the widely used log-law for the vertical pro le of velocity does not appropriately model the velocity distribution in this particular channel shape. Considering the results obtained for the span- and depth-wise velocity distributions, especially the distortion of the isovels and the location of maximum velocity, there are strong evidences of secondary currents that are present in this channel cross section. Keywords: V-shaped bottom channel; Uniform ow; Velocity distribution; Depth-averaged velocity; Boundary shear stress.