Papers by Mir Jafar Sadegh Safari
Self-cleansing is a substantial aspect of the drainage systems in which it is desired to minimize... more Self-cleansing is a substantial aspect of the drainage systems in which it is desired to minimize the sediment deposition that can cause channel blockage and surcharge early overflows. In the conventional self-cleansing design criteria of drainage systems, a single value of velocity or shear stress is used based on experience. In the recent decades rather than using a single value, non-deposition design concept has been further modified to develop self-cleansing models based on higher number of parameters considering flow, fluid, sediment and channel characteristics. However, non-deposition self-cleansing models have
been mostly developed for circular channels, and none of the models considers yet the effect of channel cross-section although some models take into account the pipe diameter, hydraulic radius and cross-section area as independent variables. In this study, a self-cleansing model
considering the effect of cross-section by a shape factor available in the literature is developed to determine the non-deposition particle Froude number for bed load sediment transport. The model is developed using experimental data of circular, rectangular and U-shape channel cross-sections from the literature; and data of trapezoidal channel cross-section from experiments carried out in this study. For validation of the model, data collected in this study is used together with four different sources of data taken from the literature. Validation of the model for each cross-section data shows its wide range applicability in terms of
different channel cross-sections.
Journal of Hydrology, 2016
Experimental data available in the literature are used in this study for the investigation of thr... more Experimental data available in the literature are used in this study for the investigation of threshold condition and sediment transport in incipient deposition condition. Using data from three different rigid boundary channel cross-sections, namely, rectangular, circular and U-shape, a unique equation is obtained for calculating flow velocity at the moment of sediment incipient deposition. The sediment transport models for incipient deposition condition are proposed in general and for different cross-section of channels. The derived equations are compared with other models in the literature. It is concluded that threshold condition of sediment motion has a range its higher and lower boundaries are related to the incipient deposition and incipient motion of particles, respectively. Results seem to be efficient to hydraulic engineers for designing drainage systems.
DE GRUYTER, Feb 2014
The condition of incipient motion and deposition are of the essential issues for the study of sed... more The condition of incipient motion and deposition are of the essential issues for the study of sediment transport. This phenomenon is of great importance to hydraulic engineers for designing sewer, drainage as well as other rigid boundary channels. This is a study carried out with the objectives of describing the effect of cross-sectional shape on incipient motion and deposition of particles in rigid boundary channels. In this research work, the experimental data given by Loveless (1992) and Mohammadi (2005) are used. On the basis of the critical velocity approach, a new incipient motion equation for a V-shaped bottom channel and incipient deposition of sediment particles equations for rigid boundary channels having circular, rectangular, and U-shaped cross sections are obtained. New equations were compared to the other incipient motion equations. The result shows that the cross-sectional shape is an important factor for defining the minimum velocity for no-deposit particles. This study also distinguishes incipient motion of particles from incipient deposition for particles. The results may be useful for designing fixed bed channels with a limited deposition condition.
2nd Caspian International Aqua Technologies Conference, 10-12 April, 2014, Baku, Azerbaijan, Apr 2014
The experimental study on sediment transport in incipient motion and deposition conditions have b... more The experimental study on sediment transport in incipient motion and deposition conditions have been carried out in a trapezoidal rigid boundary channel. Using classical dimensionless parameters of critical shear stress, grain size, particle Reynolds number, critical particle Froude number and relative particle size, new models for calculating critical shear stress and critical velocity of flow in incipient motion and deposition conditions are presented. It is concluded, threshold condition of sediment motion has a range with higher and lower boundaries that are related to the incipient deposition and incipient motion, respectively.
Deposition of sediment particles is an essential economical and technical problem for the design ... more Deposition of sediment particles is an essential economical and technical problem for the design of conveyance carrying sediment laden channels such as sewers, irrigation channels and in general, rigid boundary channels. This paper focuses on the artificial neural network (ANN) analysis technique used to estimate the critical flow velocity for incipient deposition condition of sediment particles in rigid boundary channels. This is achieved by training the network to extrapolate experimental data which are available in literature. The arranging of flow and sediment variables applied in the methods based on the prior knowledge of the traditional analysis, using the laws of hydrodynamics. Three different ANN techniques, namely radial basis function-based neural network (RBF), generalized regression neural network (GRNN) and feed-forward back propagation (FFBP) are applied. It may be concluded that all three methods have well performance in estimation of water critical velocity for incipient deposition of particles. The forecast results are in good agreement with the measured ones. A simulation also shows that the FFBP model is superior to the other two ANN techniques. The results reveals that ANN technique can efficiently estimate critical velocity of flow using six input factors, including: the flow discharge, flow depth, channel bed slope, hydraulic radius, sediment concentration and median size of sediment particles.
The criterion of incipient motion and incipient deposition best responds to the need of optimizin... more The criterion of incipient motion and incipient deposition best responds to the need of optimizing the conveyance characteristics in open channels by providing its maximum sediment carrying capacity with no sedimentation. An experimental study carried out by the objectives of the investigation of threshold condition for sediment particles. In this research work, the experimental data collected by Loveless (1992) are used. Using data taken from four different rigid boundary channel cross sections namely: rectangular, circular, oval and U-shaped, a unit equation is obtained based on the critical velocity approach for calculating incipient deposition velocity of sediment particles. New equation is compared with other incipient motion equations in rigid and loose boundary channels. The effect of cross sectional shape on sediment threshold is also clarified herein. This study manifestly distinguishes incipient motion velocity from incipient deposition velocity. The results seem efficient to hydraulic engineers for designing any drainage channels systems.
The condition of incipient motion is one of the essential issues for the study of sediment transp... more The condition of incipient motion is one of the essential issues for the study of sediment transport. This phenomenon is of great importance to hydraulic engineers for designing drainage systems. A study carried out by the objectives of describing the effect of cross-sectional shape on incipient motion of particles in rigid boundary channels. In this research the experimental data of Loveless (1992) and Mohammadi (2005) are used. The new incipient motion equation for V-shaped bottom rigid boundary channel and incipient deposition of sediment particles equations for rigid boundary channels with circular, rectangular and U-shaped cross section are obtained based on the critical velocity approach. New equations were compared with other incipient motion equations. This study distinguishes incipient motion from incipient deposition. The results may be useful for the design of fixed bed channels with limited deposition condition.
SID, 2013
Rigid boundary channels are widely used as water conveys in surface drainage, sewers and other sy... more Rigid boundary channels are widely used as water conveys in surface drainage, sewers and other systems. In order to do optimum and economic design, consideration of the movement of sediment particles is quite important. In this research, experimental data of incipient deposition and incipient motion of sediment particles are used. Applying critical velocity approach, new equations for incipient deposition of sediment particles in rigid boundary channels having circular, rectangular and U-shaped cross sections and also a new incipient motion equation for a V-shaped cross section are presented. Those equations are compared with available equations given by critical velocity approach for incipient motion of sediment particles in rigid and loose boundary channels. The present research reveals the difference between incipient deposition and incipient motion, indeed. Herein, the effect of cross sectional shape on incipient deposition and incipient motion of sediment particles in rigid boundary channels are also considered. Analysis of the results using the estabilished equations for incipient deposition of the sediment particles in channels with different cross section shapes shows that rectangular channels require a lower critical velocity and U-shaped channels need a higher amount. This result clearly states the effect of cross sectional shape on incipient deposition for sediment particles in rigid boundary channels. Because of the lack of available data, the present analysis can be usefull for developing numerical models in rigid boundary channels.
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Papers by Mir Jafar Sadegh Safari
been mostly developed for circular channels, and none of the models considers yet the effect of channel cross-section although some models take into account the pipe diameter, hydraulic radius and cross-section area as independent variables. In this study, a self-cleansing model
considering the effect of cross-section by a shape factor available in the literature is developed to determine the non-deposition particle Froude number for bed load sediment transport. The model is developed using experimental data of circular, rectangular and U-shape channel cross-sections from the literature; and data of trapezoidal channel cross-section from experiments carried out in this study. For validation of the model, data collected in this study is used together with four different sources of data taken from the literature. Validation of the model for each cross-section data shows its wide range applicability in terms of
different channel cross-sections.
been mostly developed for circular channels, and none of the models considers yet the effect of channel cross-section although some models take into account the pipe diameter, hydraulic radius and cross-section area as independent variables. In this study, a self-cleansing model
considering the effect of cross-section by a shape factor available in the literature is developed to determine the non-deposition particle Froude number for bed load sediment transport. The model is developed using experimental data of circular, rectangular and U-shape channel cross-sections from the literature; and data of trapezoidal channel cross-section from experiments carried out in this study. For validation of the model, data collected in this study is used together with four different sources of data taken from the literature. Validation of the model for each cross-section data shows its wide range applicability in terms of
different channel cross-sections.