An assessment of a new settling velocity parameterisation for cohesive sediment transport modeling
An assessment of a new settling velocity parameterisation for cohesive sediment transport modeling. Baugh, J.V.and Manning, A.J. Continental Shelf Research, 27, issue 13 (doi:10.1016/j.csr.2007.03.003 ). 18351855 . Full text not available from this repository. Official URL:  http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VBJ4NF7Y8S1&_user=5761805&_coverDate=07%2F15%2F2007&_rdoc=6&_fmt=high&_orig=browse&_srch=docinfo(%23toc%235928%232007%23999729986%23662248%23FLA%23display%23Volume)&_cdi=5928&_sort=d&_docanchor 

Abstract:  An important element within the Defra funded Estuary Process Research project “EstProc” was the implementation of the new or refined algorithms, produced under EstProc, into cohesive sediment numerical models. The implementation stage was important as any extension in the understanding of estuarine processes from EstProc was required to be suitable for dissemination into the wider research community with a level of robustness for general applications demonstrated. This report describes work undertaken to implement the new Manning Floc Settling Velocity Model, developed during EstProc. All Manning component algorithms could be combined to provide estimates of mass settling flux. The algorithms are initially assessed in a number of 1D scenarios, where the Manning model output is compared against both real observations and the output from alternative settling parameterisations. The Manning model is then implemented into a fully 3D computational model (TELEMAC3D) of estuarine hydraulics and sediment transport of the Lower Thames estuary. The 3D model results with the Manning algorithm included were compared to runs with a constant settling velocity of 0.5 mm s−1 and settling velocity based on a simple linear multiplier of concentration and with the above mentioned observations of suspended concentration. The findings of the 1D case studies found the Manning empirical settling model could reproduce 93% of the total mass settling flux observed over a spring tidal cycle. The floc model fit was even better within the turbidity maximum (TM) zone. A constant 0.5 mm s−1 only estimated 15% of the TM mass flux, whereas the fixed 5 mm s−1 settling rate overpredicted the TM mass flux by 47%. Both settling velocity as a simple linear function of concentration, and van Leussen's method, did not fare much better estimating less than half the observed flux during the various tidal and subtidal cycle periods. When the Manningsettling model was applied to a layer with suspended concentrations approaching 6 g l−1, it calculated 96% of the observed mass flux. The main conclusions of the implementation exercise were that it was feasible to implement a complex relationship between settling velocity and concentration in a 3D computational model of estuarine hydraulics, without producing any significant increase in model run times or reducing model stability. The use of the Manning algorithm greatly improved the reproduction of the observed distribution of suspended concentration both in the vertical and horizontal directions compared to the other simulations. During the 1D assessments, the Manningsettling model demonstrated flexibility in adapting to a wide range of estuarine environmental conditions (i.e. shear stress and concentration), specifically for applied modelling purposes. 

Item Type:  Article 

Subjects:  Floods > River management Coasts > Sediment transport and scour 

ID Code:  369 

Deposited On:  11 Feb 2010 09:55 

Last Modified:  11 Feb 2010 09:55 

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