On the development of dunes in erodible channels

1974 ◽  
Vol 64 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Jørgen Fredsøe
Keyword(s):  
Stability Analysis ◽  
Order Approximation ◽  
Experimental Fact ◽  
Bed Load ◽  
Two Dimensional ◽  
Alluvial Channel ◽  
Load Transport ◽  
Bed Load Transport ◽  
The Stability ◽  
Vorticity Transport

A two-dimensional stability analysis of the flow in a straight alluvial channel has been carried out, using the vorticity transport equation. In the analysis an attempt has been made to account for the influence of gravity on bed-load transport, and this turned out to change the stability quite significantly.In the case of instability, the further growth of the dunes has been investigated using a second-order approximation, This nonlinear theory explains the experimental fact that the dunes very soon become asymmetric.

Meandering and braiding of rivers

1978 ◽  
Vol 84 (4) ◽  
pp. 609-624 ◽  
Author(s):  
Jørgen Fredsøe
Keyword(s):  
Laboratory Experiments ◽  
Bed Load ◽  
Two Dimensional ◽  
Transport Mechanisms ◽  
Dimensional Model ◽  
Alluvial Rivers ◽  
Load Transport ◽  
Bed Load Transport ◽  
The Stability ◽  
Natural Rivers

The origin of meandering and braiding of alluvial rivers is re-analysed in terms of stability theory. The flow is described by a two-dimensional model, and the transportation of sediment is separated into bed-load transport and transport of suspended sediment, by use of the improved knowledge of sediment transport mechanisms achieved in recent years. The paper explains why it is important to distinguish between the sediment transported as bed load and that in suspension.The analysis is able to predict whether a river remains stable or tends to meander or braid.The results of the stability analysis are compared with laboratory experiments and data from natural rivers, and the agreement is satisfactory.

On the formation of ripples on an erodible bed

1984 ◽  
Vol 144 ◽  
pp. 177-190 ◽  
Author(s):  
B. Mutlu Sumer ◽  
Mehmet Bakioglu
Keyword(s):  
Reynolds Number ◽  
Stability Analysis ◽  
Linear Stability Analysis ◽  
Present Theory ◽  
Bed Load ◽  
Wave Stability ◽  
Load Transport ◽  
Bed Load Transport ◽  
Limiting Values ◽  
Good Agreement

A linear stability analysis is presented of both hydraulically smooth and transitional flows over an erodible bed. The present theory is developed to account for the formation of ripples. It is essentially an extension of the theory of Richards (1980) to include the effect of viscosity upon the bed wave stability. The theory takes into consideration that the formation of ripples does not depend on flow depths, and that only the bed-load transport is involved in the formation of ripples. The effect of gravity is included in the analysis through the local inclination of the wavy bed surface. The results show that the bed is unstable (i.e. ripples exist) when the grain Reynolds number is less than a certain value. The limiting values of the grain Reynolds number for ripple existence obtained through present analysis are found to be in good agreement with observations.

scholarly journals Two-Dimensional Numerical Simulation Study on Bed-load Transport in Fluctuating Backwater Area: A Case-Study Reservoir in China

2018 ◽  
Author(s):  
Ming Luo ◽  
Heli Yu ◽  
Er Huang ◽  
Rui Ding ◽  
Xin Lu
Keyword(s):  
Sediment Transport ◽  
Transport Model ◽  
Longitudinal Section ◽  
Bed Load ◽  
Two Dimensional ◽  
River Bed ◽  
Reservoir Drawdown ◽  
Load Transport ◽  
Bed Load Transport ◽  
Volume Method

Numerical modeling of sedimentation and erosion in reservoirs is an active field of reservoir research. However, simulation of bed-load transport phenomena has rarely been applied to other water bodies, in particular, the fluctuating backwater area. This is because the complex morphological processes between hydrodynamics and sediment transport are generally challenging to accurately predict. In this study, the refinement and application of a two-dimensional shallow-water and bed-load transport model to the fluctuating backwater area is described. The model employs the finite volume method of the Godunov scheme and saturated sediment transport equations. The model was verified against experimental data of a scaled physical model. It was then applied to actual reservoir operation, including reservoir storage, reservoir drawdown and continuous flood process, to predict the morphology of reservoir sedimentation and sediment transport rates and bed level changes in the fluctuating backwater area. It was found that the location and morphology of sedimentation effected by the downstream water level results in random evolution of the river bed, and bed-load sedimentation is transported from upstream to downstream with the slope of the longitudinal section of the river bed generally reduced. Moreover, the sediment is mainly deposited in the main channel and the elevation difference between the riverbank and channel decreases gradually.

scholarly journals Whit ham method of the expansion near the wave front propagating on the river with bed load transport

1990 ◽  
Vol 12 (3) ◽  
pp. 8-14
Author(s):  
Pham Hung
Keyword(s):  
Differential Equation ◽  
Wave Front ◽  
Water Surface ◽  
Bed Load ◽  
Flood Wave ◽  
Load Transport ◽  
Bed Load Transport ◽  
Linear Differential ◽  
The Stability ◽  
Special Case

In this paper the non linear differential equation describing the behavior of water surface behind the wave front is obtained by Whit ham method. It is shown that the bed load transport could influence significantly on the stability of the flood wave. In the supercritical flow, the bed load wave will propagate upstream and will linearly stabilize. The different situations when the wave could topple over are analyzed. In the flow without the bed load transport, the results of Whit ham have been reobtained as a special case.  

Instability of erodible beds

1970 ◽  
Vol 42 (2) ◽  
pp. 225-244 ◽  
Author(s):  
Frank Engelund
Keyword(s):  
Mathematical Model ◽  
Internal Friction ◽  
Potential Flow ◽  
Transport Mechanism ◽  
Flow Analysis ◽  
Two Dimensional ◽  
Alluvial Channel ◽  
The Stability ◽  
Vorticity Transport ◽  
Erodible Beds

The stability of a sand bed in an alluvial channel is investigated by a two-dimensional mathematical model, based on the vorticity transport equation. The model takes account of the internal friction and describes the non-uniform distribution of the suspended sediment. It turns out that the inclusion of the friction and of a definite model of the sediment transport mechanism leads to results rather different from those obtained previously by potential-flow analysis.

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