Sand and Mud Properties
The settling velocity is the most important property of cohesive flocs in the coastal environment. For the present purposes, time-dependent floc properties are represented by the floc diameter, density and shear strength. Aggregation, which includes floc growth and breakup due to collisions and shearing in turbulent flows, is modeled for flocs treated as fractal geometries. Based data from the Tamar estuary in UK, it is shown that the settling velocity depends on the time-history of the flow shear rate and the solids volume fraction. This observation is used to discuss a well-known analytic expression for estimating the settling velocity.