Design criteria for sediment transport in sewers based on self-cleansing concept

Abstract

This study of bed-load transport was undertaken on the basis of laboratory data in two states, i.e., limit of deposition and deposited bed, by using new design criteria, whereby, compared to earlier similar studies, fewer parameters were considered, yet with almost the same or in some cases an even greater level of accuracy. The modified criterion in the new design for transport in the limit of deposition was using only three dimensionless parameters, i.e., Froude number, volumetric concentration of sediment, and relative size of the grain. But the new design criterion applied to the deposited bed case used four dimensionless parameters, i.e., three parameters used for the preliminary case besides the relative thickness of sedimentation. Compared with other known relationships in sediment transport, the produced equations introduced here yield better results than previous studies. With the lessened number of parameters, the results are much easier to obtain.

Design of a fuzzy differential evolution algorithm to predict non-deposition sediment transport

“…According to the table and all indicators, the proposed model produced better results than the regression equations. Among the presented models, most indicators for May et al (1996) equation indicated better results than Ebtehaj et al (2014), but the difference is not significant enough to deem one better than another. It is worth noting that May et al (1996) equation was superior to other equations in terms of MSE, MAE, MARE and d, and a lower R 2 ; therefore, it is quite different from the estimate achieved by May et al (1996), which increases its unreliability.…”

“…5. The DR values for ANFIS-DE, and Ebtehaj et al (2014) and May et al (1996) equations are 0.99, 1.03 and 0.97, respectively. Although the difference is not vast, model accuracy and the average precision should be confirmed by considering the maximum relative error values as well.…”

“…The data employed in this study are all associated with non-deposition in different hydraulic conditions, such as pipe diameter, channel slope, particle size and channel length. Details of the datasets are provided in studies carried out by Ebtehaj et al (2014) and Ebtehaj and Bonakdari (2014a, b …”

“…The simplest traditional method is to use a constant limiting velocity value provided in many references for different hydraulic and geographical situations (see more details in Ebtehaj et al 2014). This method is inaccurate in some circumstances because the values do not consider hydraulic and sediment characteristics, such as pipe diameter, flow depth, hydraulic radius, median particle diameter and volumetric sediment concentration.…”

“…2), A is the cross-sectional area of the flow, g is the gravitational acceleration, s (=q s /q) is the specific gravity of sediment and y is the flow depth. Ebtehaj et al (2014) presented a regression-based equation to determine the densimetric Froude number (Fr) by dimensional analysis with a wide range of data as follows:…”