scholarly journals Wave Period and Grain Size Controls on Short‐Wave Suspended Sediment Transport Under Shoaling and Breaking Waves

2019 ◽  
Vol 124 (12) ◽  
pp. 3124-3142
Author(s):  
Drude F. Christensen ◽  
Michael G. Hughes ◽  
Troels Aagaard
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Suspended Sediment ◽  
Breaking Waves ◽  
Short Wave ◽  
Wave Period ◽  
Suspended Sediment Transport

scholarly journals "Soft" shore protection by a beach drain system

2013 ◽  
Vol 15 (3) ◽  
pp. 295-304
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Seepage Flow ◽  
Breaking Waves ◽  
Suspended Sediment Transport ◽  
Swash Zone ◽  
Shore Protection ◽  
Boussinesq Model ◽  
Drain Pipe ◽  
Porous Flow

<p>In this study, the effects of seepage flow in the swash zone on beach profile evolution under the wave action are examined numerically. The seepage flow is induced artificially by a porous drain pipe buried beneath swash zone parallel to the coastline. The system includes minimal environmental impact compared with the hard protection methods. A higher order Boussinesq model for breaking and non-breaking waves is extended in the swash zone and is coupled with a porous flow model, in order to take into account the influence of infiltration-exfiltration processes in the sediment transport. This influence is introduced in a simple and well-proven sediment transport formula by using a new modified Shields parameter, which is derived after the modification of the shear stress and the immerged sediment weight. In order to incorporate the suspended sediment transport rate, the depth-integrated transport equation for suspended sediment is solved. Model results are compared with experimental data. The agreement between numerical simulations and experiment is quite satisfactory. It is concluded that the beach drainage method is efficient for shore protection from erosion.</p>

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

2013 ◽  
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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