Experimental observation of the flow structure of turbidity currents

Nourmohammadi, Zahra; Afshin, Hossein; Firoozabadi, Bahar

doi:10.1080/00221686.2010.543777

Cited by 30 publications

(33 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[], Islam and Imran [], and Nourmohammadi et al . [] are overlapped on the computed curves in Figure for comparison. It is found that the values ξ = 0.6 and χ = 2.2 ensure a satisfactory agreement of equation with the experimental data.…”

Section: Velocity Distributionmentioning

confidence: 99%

See 1 more Smart Citation

Hydrodynamic analysis of fully developed turbidity currents over plane beds based on self‐preserving velocity and concentration distributions

et al. 2015

View full text Add to dashboard Cite

This paper presents a hydrodynamic analysis for the fully developed turbidity currents over a plane bed stemming from the classical three‐equation model (depth‐averaged fluid continuity, sediment continuity, and fluid momentum equations). The streamwise velocity and the concentration distributions preserve self‐similarity characteristics and are expressed as single functions of vertical distance over the turbidity current layer. Using the experimental data of turbidity and salinity currents, the undetermined coefficients and exponents are approximated. The proposed relationships for velocity and concentration distributions exhibit self‐preserving characteristics for turbidity currents. The depth‐averaged velocity, momentum, and energy coefficients are thus obtained using the proposed expression for velocity law. Also, from the expressions for velocity and concentration, the turbulent diffusivity and the Reynolds shear stress distributions are deduced with the aid of the diffusion equation of sediment concentration and the Boussinesq hypothesis. The generalized equation of unsteady nonuniform turbidity current is developed by using the velocity and concentration distributions in the moments of the integral scales over the turbidity current layer. Then, the equation is applied to analyze the gradually varied turbidity currents considering closure relationships for boundary interaction and shear velocity. The streamwise variations of current depth, velocity, concentration, reduced sediment flux, and Richardson number are presented. Further, the self‐accelerating and depositional characteristics of turbidity currents including the transitional feature from erosional to depositional modes are addressed. The effects of the streamwise bed slope are also accounted for in the mathematical derivations. The results obtained from the present model are compared with those from the classical model.

show abstract

Section: Velocity Distributionmentioning

confidence: 99%

“…Besides, from Nourmohammadi et al . [], the experimental data for run 3 at streamwise distances of 2.5 and 3.5 m, run 10 at 4.5 m, and runs 7 and 8 at 3.5 and 4.5 m, respectively, from the flume inlet are used. Finally, the computed velocity distribution of Altinakar et al .…”

Section: Velocity Distributionmentioning

confidence: 99%

Hydrodynamic analysis of fully developed turbidity currents over plane beds based on self‐preserving velocity and concentration distributions

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Table 2 compares the average of these constants for different beds with those of Altinkar et al (1996) and Nourmohammadi et al (2011). Note that their tests were sediment-laden over the smooth bed with inlet Froude number between 1-2.33 and 0.6-3.6 for the Altinkar and Nourmohammadi tests, respectively, while, inlet Froude number over the smooth bed in the present study was between 0.65-0.85 and 0.30-0.45 in the saline and sediment-laden density currents, respectively.…”

Section: Verification Of Experimentationmentioning

confidence: 90%

“…The effect of friction at the top boundary on the velocity profile is considered by modeling a dense stratified layer of limited thickness between two homogeneous fluids (Nourmohammadi et al 2011). Accordingly, the velocity profile of jet region is determined by a semi-Gaussain equation (Altinakar et al 1996):…”

Section: Verification Of Experimentationmentioning

confidence: 99%

Experimental observation of saline underflows and turbidity currents, flowing over rough beds

et al. 2015

View full text Add to dashboard Cite

Density currents are formed when gravity acts upon a density difference between two different fluids, and the driving force is the buoyancy force. These currents are the most important transport mechanisms and deposition of noncohesive sediments in narrow and deep reservoirs. In this research, 126 experiments were performed to investigate the effects of artificial bed roughness on saline and sediment-laden density currents. Conic and cylindrical shapes of roughness were used with three different heights. Velocity and concentration profiles were measured in 4 and 3 cross-sections, respectively. Presence of roughness causes increasing density current body thickness, decreasing maximum value of velocity and increasing distance of peak value of velocity point from the bed in the normal velocity profile. Coefficient of entrainment in the rough beds was more than smooth bed and boosted for greater roughness heights. A special behavior, named as "Lifting phenomenon", was appeared in some of the tests which effects on the velocity profiles.

show abstract

“…However, these cannot provide enough and effective information to quantify the whole process of reservoir turbidity currents. Also, laboratory experiments have been used to investigate the evolutional characteristics of turbidity currents (Hürzeler et al 1996;Lee and Yu 1997;Gladstone et al 1998;Hallworth and Huppert 1998) and the vertical structure of the currents (Altinakar et al 1996;Eggenhuisen and McCaffrey 2012;Nourmohammadi et al 2011). Especially, Lee and Yu (1997) performed a series of tests to investigate the formation and propagation of turbidity currents attributable to sustained inflow and in particular demonstrated the impacts of various upstream and downstream boundary conditions.…”

Section: Introductionmentioning

confidence: 99%

Whole-Process Modeling of Reservoir Turbidity Currents by a Double Layer-Averaged Model

Cao

Pender

et al. 2015

J. Hydraul. Eng.

View full text Add to dashboard Cite

Turbidity current is formed as subaerial open-channel sediment-laden flow plunges into a reservoir. The whole process of reservoir turbidity current, i.e., formation, propagation, and recession, is generally controlled by the water and sediment inputs from upstream and also the reservoir operation scheme specifying the downstream boundary condition. Enhanced understanding of reservoir turbidity current is critical to effective sediment management in alluvial rivers. However, until now there has been a lack of physically based and practically feasible models for resolving the whole process of reservoir turbidity current. This is because the computing cost of three-dimensional modeling is excessively high. Also, single layer-averaged models cannot resolve the formation process characterized by the transition from open-channel sediment-laden flow to subaqueous turbidity current, or the upper clear-water flow as dictated by the operation scheme of the reservoir, which has significant impacts on turbidity current. Here a new two-dimensional double layer-averaged model is proposed to facilitate for the first time whole-process modeling of reservoir turbidity current. The two hyperbolic systems of the governing equations for the two layers are solved separately and synchronously. The model is well balanced because the interlayer interactions are negligible compared with inertia and gravitation, featuring a reasonable balance between the flux gradients and the bed or interface slope source terms and thus applicable to irregular topographies. The model is benchmarked against a spectrum of experimental cases, including turbidity currents attributable to lock-exchange and sustained inflow. It is revealed that an appropriate clear-water outflow is favorable for turbidity current propagation and conducive to improving sediment flushing efficiency. This is significant for optimizing reservoir operation schemes. As applied to turbidity current in the Xiaolangdi Reservoir in the Yellow River, China, the model successfully resolves the whole process from formation to recession. The present work facilitates a viable and promising framework for whole-process modeling of turbidity currents, in support of reservoir sediment management.

show abstract

Experimental observation of the flow structure of turbidity currents

Cited by 30 publications

References 21 publications

Hydrodynamic analysis of fully developed turbidity currents over plane beds based on self‐preserving velocity and concentration distributions

Hydrodynamic analysis of fully developed turbidity currents over plane beds based on self‐preserving velocity and concentration distributions

Experimental observation of saline underflows and turbidity currents, flowing over rough beds

Whole-Process Modeling of Reservoir Turbidity Currents by a Double Layer-Averaged Model

Contact Info

Product

Resources

About