Effect of particle concentration on sediment and turbulent diffusion coefficients in open-channel turbulent flow

To achieve a complete knowledge about the effect of particle concentration on sediment and turbulent diffusion coefficients in open-channel turbulent flow is a long-standing problem for the community of researchers. The effect of particle concentration is investigated on the sediment and turbulent diffusion coefficients through the inverse of turbulent Schmidt number or β which is defined by the ratio of sediment diffusion coefficient to turbulent diffusion coefficient. It is observed that with increasing particle concentration, the sediment diffusion coefficient decreases more in comparison with the turbulent diffusion coefficient for both dilute and non-dilute sediment-laden flows. The physical characteristics of β observed are expressed mathematically in terms of normalized settling velocity, reference level and reference concentration. The applicability of the mathematical formulae is confirmed by the agreement analysis between experimental data and particle concentration profile computed from the Rouse equations modified through the newly proposed expression of β. Apart from the better agreement between dilute particle concentration data and the developed Rouse equation, the striking observation is that the modified Rouse equation shows reasonable computational accuracy for non-dilute particle concentration data also. Minimum error is obtained from the present model when it is compared with the models proposed by the previous researchers.