Flood Suspended Sediment Transport: Combined Modelling from Dilute to Hyper-Concentrated Flow

During flooding, the suspended sediment transport usually experiences a wide-range of dilute to hyper-concentrated suspended sediment transport depending on the local flow and ground conditions. This paper assesses the distribution of sediment for a variety of hyper-concentrated and dilute flows. Due to the differences between hyper-concentrated and dilute flows, a linear-power coupled model is proposed to integrate these considerations. A parameterised method combining the sediment size, Rouse number, mean concentration, and flow depth parameters has been used for modelling the sediment profile. The accuracy of the proposed model has been verified against the reported laboratory measurements and comparison with other published analytical methods. The proposed method has been shown to effectively compute the concentration profile for a wide range of suspended sediment conditions from hyper-concentrated to dilute flows. Detailed comparisons reveal that the proposed model calculates the dilute profile with good correspondence to the measured data and other modelling results from literature. For the hyper-concentrated profile, a clear division of lower (bed-load) to upper layer (suspended-load) transport can be observed in the measured data. Using the proposed model, the transitional point from this lower to upper layer transport can be calculated precisely.

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Suspended sediment transport in rigid boundary channels at limit deposition

Water Science & Technology ◽

10.2166/wst.1998.0036 ◽

1998 ◽

Vol 37 (1) ◽

pp. 147-154 ◽

Cited By ~ 6

Author(s):

Chandramouli Nalluri ◽

Fabio Spaliviero

Keyword(s):

Experimental Data ◽

Sediment Transport ◽

Suspended Sediment ◽

Technical Problem ◽

Friction Model ◽

Suspended Sediment Transport ◽

Rigid Boundary ◽

Sediment Size ◽

Wide Range ◽

The University

Sedimentation or deposition of sediments is a crucial economical and technical problem for the design of conveyances carrying sediment laden flow such as sewers, irrigation canals and, in general, rigid boundary channels. In light of investigations on sediment transport at the limit of deposition carried out during the last two decades at the University of Newcastle upon Tyne, experimental data on suspended sediment transport collected by Pulliah (1978), Macke (1982) and Arora (1983) are analysed. The data cover a wide range of volumetric concentrations (3.7 to 48542 ppm) and sediment size (0.006 to 0.37 mm). A new model for the prediction of suspended sediment transport in rigid boundary channels at limit deposit is proposed. The model was fitted by multiple regression analysis to Macke's (1982) and Arora's (1983) experimental data. Pulliah's (1978) data validate the relation. Nalluri et al. (1994) bed load friction model is checked with available data and a good agreement is observed.

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2D and 3D CFD Investigations of Seabed Shear Stresses Around Subsea Pipelines

Volume 4A: Pipeline and Riser Technology ◽

10.1115/omae2013-10626 ◽

2013 ◽

Cited By ~ 1

Author(s):

Wenwen Shen ◽

Terry Griffiths ◽

Mengmeng Xu ◽

Jeremy Leggoe

Keyword(s):

Sediment Transport ◽

Suspended Sediment ◽

Interaction Model ◽

Suspended Sediment Transport ◽

Shear Stresses ◽

Parametric Function ◽

Ample Evidence ◽

North West ◽

Wide Range ◽

Subsea Pipelines

For well over a decade it has been widely recognised that existing models and tools for subsea pipeline stability design fail to account for the fact that seabed soils tend to become mobile well before the onset of pipeline instability. Despite ample evidence obtained from both laboratory and field observations that sediment mobility has a key role to play in understanding pipeline/soil interaction, no models have been presented previously which account for the tripartite interaction between the fluid and the pipe, the fluid and the soil, and the pipe and the soil. There are numerous well developed and widely used theories available to model pipe-fluid and pipe-soil interactions. A challenge lies in the way to develop a satisfactory fluid-soil interaction algorithm that has the potential for broad implementation under both ambient and extreme sea conditions due to the complexity of flow in the vicinity of a seabed pipeline or cable. A widely used relationship by Shields [1] links the bedload and suspended sediment transport to the seabed shear stresses. This paper presents details of computational fluid dynamics (CFD) research which has been undertaken to investigate the variation of seabed shear stresses around subsea pipelines as a parametric function of pipeline spanning/embedment, trench configuration and wave/current properties using the commercial RANS-based software ANSYS Fluent. The modelling work has been undertaken for a wide range of seabed geometries, including cases in 3D to evaluate the effects of finite span length, span depth and flow attack angle on shear stresses. These seabed shear stresses have been analysed and used as the basis for predicting sediment transport within the Pipe-Soil-Fluid (PSF) Interaction Model [2] in determining the suspended sediment concentration and the advection velocity in the vicinity of pipelines. The model has significant potential to be of use to operators who struggle with conventional stabilisation techniques for the pipelines, such as those which cross Australia’s North West Shelf, where shallow water depths, highly variable calcareous soils and extreme metocean conditions driven by frequent tropical cyclones result in the requirement for expensive and logistically challenging secondary stabilisation measures.

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