Bed-load transport at high shear stress: With application to friction in rivers and sand waves

The knowledge of the hydrodynamic behaviour of bed-load transport over mobile boundaries at high shear stress is of great importance. The understanding of this behaviour is required in the proper engineering and economic design of projects relating to erosion and shoaling of rivers, irrigation canals and navigation channels.;Experimental observations were made for both the upper plane-bed regime and sand-wave regime, using various bed materials: sand (with particle diameters; 1.1 mm, 0.55 mm, and 0.354 mm), bakelite (1.05 mm and 0.674 mm), and nylon (3.94 mm). Measurements for the stationary plane bed were taken for flows at inclination angles ranging between 0;The evaluation of the computer models using the experimental results was found to show generally good agreement for the upper plane-bed regime. Comparison of the frictional behaviour of the upper plane-bed regime and sand-wave regime clearly shows two distinctly different patterns. The shift from sand-wave regime to upper plane-bed regime was found to occur in the range between 0.8 and 1.0 of the measured dimensionless shear stress.;A computer algorithm previously used to investigate the frictional behaviour of the mobile boundary at high shear stress was extended while considering variation of shear stress with height within the shear layer and a curvilinear relation for the contact-load concentration distribution within this layer. The revised algorithm was used to model the frictional behaviour of the mobile boundary, and the bed-load transport rate when flows were both horizontal and inclined. Analytical study of the shift from the sand-wave regime to the upper plane-bed regime was also considered.