A DYNAMIC APPROACH TO SEDIMENT-LADEN TURBULENT FLOWS

An approach that studies the effects of the dynamic coupling between t urbulent flow and sediment in suspension on the mean velocity and the sediment concentration profiles of sediment-laden open-channel flows i s systematically developed. The analysis is based on the Boussinesq ap proximation to the governing equations that treats the mixture of the liquid and sediment as a single fluid with changing density over the f low depth. As a result, it permits the direct systematic comparison be tween the turbulent flow of clear water and that with suspended sedime nt. By further employing the mixing length approach for the related tu rbulent closure problem, the coupling effects on mean velocity and con centration profiles are evaluated, and the resulting distributions are compared with available experimental data. The derived mean velocity distribution contains profiles of existing models as special cases and thus unifies the results of existing major models conceptually and qu antitatively. Moreover, the analysis clearly demonstrates the importan ce of the coupling effect on the suspended sediment concentration prof ile and, consequently, a more generalized formula of concentration pro file is obtained. Although the mean velocity and concentration profile s are the main concern of this paper, the approach establishes a frame work for further study of the effects of the dynamic interaction on ot her physical quantities.