Boundary Shear Stress Distribution in Smooth and Rough Open Channel Flow



Boundary shear distribution in open channel flow is a crucial issue for river engineer and researchers working in this area. An experimental investigation has been carried out to measure the boundary shear stress distribution along the wetted perimeter of the smooth and rough channel using piston tube technique the accuracy of the method has been compared and checked with another convention method, NDM, VDM, MPM, Velocity Profile Method and energy gradient approach. The boundary shear along the bed and wall of the channel are different for different flow depth and for different roughness conditions. The percentage of boundary shear carried by the wall and bed has been analysed and found to depends on upon non-dimensional geometry and hydraulic parameters such as Aspect ratio, Reynolds number and Froude’s number. A multi linear regression model has been applied to predict the boundary shear distribution for bed. The equation is useful to calculate the roughness coefficient (friction factor) of the wall and bed of the channel separately, which further determines the composite roughness of the open channel flow accuracy. The methodology has been applied successfully to calculate the stage discharge relationship of the open channel flow. The methodology has been validated against other experimental data, other researcher’s models and NaturalRiver.


Boundary shear stress distribution; Piston tube Technique; Aspect Ratio; Reynolds Number; Froude’s number; Roughness Coefficient; Composite Roughness

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