SHEAR DISTRIBUTION IN BENDS IN RECTANGULAR CHANNELS

The analysis is based on the assumption of forced vortex law of velocity distribution near the exit. The constant involved in the assumed mean velocity distribution is evaluated on the basis of continuity equation with the assumption that entire superelevation dies out at the exit section. The exponent of radius in the velocity distribution law is correlated with geometry of the bend and Reynolds number. Further it is assumed that a mean velocity relationship as suggested by Keulegan is valid for bend flow. The experimental data, collected in a 60 degree bend in a rectangular flume with radius to width ratio varying between 1. 5 and 6 and with three bed roughnesses, were used along with other field data to obtain information on velocity variation. The local shears were measured in the bends with the help of a preston-tube calibrated for grain roughness used in the bend.