Suspension of Large Concentrations of Sands

Existing methods based on the diffusion theory have been extended to determine the sediment concentration distribution for large concentrations of sand. The modifications for volumetric concentrations ranging from 4 to 20% include decreased fall velocity, and increased viscosity and specific weight of the suspension. The sediment concentration profiles are sensitive to the velocity profiles and the fall velocity of sediment particles. In turbulent flows, either a power law or a two-layered logarithmic law can be used to describe the velocity profiles and the sediment difiusivity. The proposed method accurately depicts the deviation from the Rouse equation at large concentrations of sands, and the agreement with sediment concentration profiles measured by Einstein and Chien is excellent. The proposed numerical solution gradually reduces to the relationships of Karim and Kennedy, and Rouse as the volumetric concentration decreases below four percent.