PHYSICAL AND NUMERICAL EXPERIMENTS ON TURBULENCE AFFECTED SEDIMENTATION

摘要

In modelling cohesive sediment transport the description of the settling velocity for the sedimentation process is of central importance. Beside many other parameters the settling velocity depends on the concentration of the suspended matter and the turbulence of the flow. Although many investigations on this topic have been carried out, the experimental examination of the settling behaviour is still improvable. In this paper an investigation concerning the settling behaviour in relation to concentration and turbulence is presented. The experimental set-up, which differs fundamentally from common facilities, is described as well as the test execution and evaluation. Particularly the supporting and destructing effect of turbulence on flocculation and finally on the settling velocity has been investigated and proved for small concentrations. The experimental results document the ability of the new facility concept and are used to derive a formula for the settling velocity. This formula has been validated in a simple 1-dim numerical model, which solves the advection-diffusion-equation. The model specifications are presented. The comparison of numerical and experimental data shows a very good agreement. The presented package of physical experiments and numerical validation was found to be an efficient way to provide the essential data for numerical simulations of complex transport problems.