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 Resources: Dredging and Offshore Engineering Lecture Notes



Home / Hopper Sedimentation /

    03-An analytical approach to the sedimentation process in trailing suction hopper dredges. (986)

For the estimation of the sedimentation process in TSHD’s a number of models have been developed. The oldest model used is the Camp (1946) model which was developed for sewage and water treatment tanks. Camp and Dobbins added the influence of turbulence based on the two-dimensional advection-diffusion equation, resulting in rather complicated equations. Groot (1981) added the effects of hindered settling. Miedema & Vlasblom (1996) simplified the Camp equations by means of regression and included a rising sediment zone, as well as hindered settling and erosion and an adjustable overflow. Van Rhee (2001) modified the implementation of erosion in the Camp model, but concluded that the influence is small due to the characteristics of the model. Ooijens added the time effect, since the previous models assume an instantaneous response of the settling efficiency on the inflow of mixture. Yagi (1970) developed a new model based on the concentration distribution in open channel flow.
The models mentioned above are all black box approaches assuming simplified velocity distributions and an ideal basin. Van Rhee (2002) developed a sophisticated model, the 2DV model. This model is based on the 2D (horizontal and vertical) Reynolds Averaged Navier Stokes equations with a k-ε turbulence model and includes suspended sediment transport for multiple fractions.
The Miedema & Vlasblom model is based on the Camp model but lacks a number of features. One can think of:
• The layer thickness of the layer of water above overflow level.
• The effect of scour during the final stage of the loading process.
• The hindered settling effect using the correct average concentration above the bed.
• The storage, time delay or buffer effect.
This article describes the basic Miedema & Vlasblom model (1996) and shows how the above features should be implemented.

Reference:

Miedema, S.A., "An Analytical Approach To The Sedimentation Process In Trailing Suction Hopper Dredgers". Terra et Aqua, September 2008.



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