Comparative Evaluation of Velocity Distribution Equations in Sediment-Laden Flow

Mohsen Nasrabadi, Mohammad Hossein Omid, Ali Mahdavi Mazdeh

Tuesday 30 june 2015

17:00 - 17:15h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling

Parallel session: 7A. Sediment - Erosion

Accurate estimation of the sediment rate is very important in sediment-laden flows. The velocity distribution is one of the most important parameters to estimate the sediment rate. Until now, many equations have been introduced by many researchers for estimating the velocity distribution in open channel flows. In this paper, eight proposed models have been examined for the velocity distribution in sediment-laden flows by a comparison with selected datasets. Such equations as power law, log law, modified log law, log-wake law, modified log-wake, log-modified wake, and parabolic law have been evaluated. The accuracy of each equation has been assessed using some statistical indices, such as, MAE, RMSE, and R2. Results have shown that logarithmic distribution only able to estimate accurately the velocity in the inner region. Comparing the equations with experimental data and based on the statistical analysis, have shown that the velocity values in both inner and outer regions are estimated with reasonable accuracy using log-wake velocity distribution (with a relative error up to about 5%). This equation is recommended for calculating the suspended sediment discharge. On the other hand, parabolic-law doesn’t have a good accuracy and it will cause large errors (with a relative error up to about 17%). In addition, because of low sediment concentration in outer layer of sediment-laden flows, the effect of suspended sediment in this layer becomes very low and can be ignored.