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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Sediment management and morphodynamics : Modelling particulate transport of sediment disposal in marine environment ¨c a near-far field coupl...
Modelling particulate transport of sediment disposal in marine environment ¨c a near-far field coupling approach
Author : S.N. CHAN (1), ADRIAN C. H. LAI (2), E. ERIC ADAMS (3) & ADRIAN W.K. LAW (4)
ABSTRACT
In marine dumping of dredged materials, sediment is usually disposed as instantaneous sources from barges and
hoppers. It is essential to quantify and assess the transport and fate of sediment particles, in order to minimize the
impact to the marine environment, and to maximize the cost effectiveness of operation. The ˇ°near fieldˇ± dynamics of an
instantaneous disposal of sediment in the open ocean is characterized by the formation of a dense two-phase thermal.
Particles are initially transported by the thermal induced vortex circulation downward, in a vertical velocity greater than
the settling velocity of individual sediment particles. As the thermal descent velocity decreases, sediment starts to settle
out from the fluid phase in their individual settling velocities, subjected to transport and mixing in the far field. This paper
presents the development of a modeling methodology for predicting the transport of coarse and fine sediment in an
instantaneous disposal operation in a moving ambient from the near field to the far field. The near field transport/descent
of sediment cloud can be predicted by an integral model accounting for the conservation of fluid volume, momentum and
buoyancy induced by sediment particles. Particle motion is solved using the Lagrangian governing equation of motion.
The far field transport and dispersion of suspended sediment in ambient current is predicted using a shallow water
hydrodynamic model, solving the Eulerian advection-diffusion equation for sediment. The two regimes are seamlessly
coupled by releasing mass sources of sediment in corresponding grid cells, when the thermal descent velocity is equal
to the particle settling velocity. Model prediction of bottom deposition profiles compares well with laboratory data of
instantaneous sediment disposal in a current. An example of model application for suspended solid impact assessment
in a tidal environment is demonstrated.
File Size : 413,108 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Sediment management and morphodynamics
Date Published : 18/08/2015
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