36. Study on the Variation of Distribution of Velocity in Accordance with Differential Roughness in a Compound Open Channel

This paper presents an experimental study in which a series of measurements were carried out to investigate the hydraulic characteristics of a wide compound open channel having high width ratio and dissimilar roughness in the main channel and flood plain boundary by using pitot tube point-wise velocity measurements. Furthermore, in order to understand the effect of differential roughness (the ratio of base Manning’s n value of floodplain surface roughness to that of the main channel) on the distribution of depth-averaged velocity and distribution of flow in the experimental channel, cases with different flow rates were studied. The contour plots of 2D iso-levels were drawn using SURFER software. As the channel is symmetric, half of the width is considered for point velocities. The variation of point velocities is considered along width-wise direction of the channel in order to study the depth-wise velocity profile distributions. The lateral variation of depth-averaged velocities was observed in the compound channel flow for different differential roughness (γ) and the variation of flow rate in main channel is also studied with the increase in differential roughness.