Analysis of Bed‐Load Motion at High Shear Stress

Recent pipeline experiments performed in Saskatchewan show the existence of a shear layer in which the solids concentration decreases linearly with height. This finding has already been used to calculate the velocity distribution within a constant-stress shear layer. The analysis has now been extended to obtain the solids discharge per unit breadth of bed. The result agrees with the modified Meyer-Peter and Muller equation and with the writer's sand data. For larger nylon particles the solids discharge per unit breadth fell below that expected on the basis of the sand data; and the new analysis shows the reason for this apparent anomaly. It also shows that a shear layer several grain-diameters thick will not be uncommon in open-channel flow. Contrary to the conventional wisdom, the new analysis predicts that the threshold-of-motion curve on the Shields diagram must approach a constant value at sufficiently small abscissae, a finding which appears to be in accord with recent experimental evidence.