intro story Coast / Estuary

Coast / Estuary

Coastal systems are among the most dynamic physical systems on earth and are subject to a large variety of forces. The morphodynamic changes occurring to coastlines worldwide are of great interest and importance. These changes occur as a result of the erosion of sediments, its subsequent transport as bed load or suspended load, and eventual deposition. 
 
Estuaries are partly enclosed water bodies that have an open connection to the coast. Estuaries generally have one or more branching channels, intertidal mudflats and/or salt marshes. Intertidal areas are of high ecological importance and trap sediments (sands, silts, clays and organic matter).
Within the Delft3D modelling package a large variation of coastal and estuarine physical and chemical processes can be simulated. These include waves, tidal propagation, wind- or wave-induced water level setup, flow induced by salinity or temperature gradients, sand and mud transport, water quality and changing bathymetry (morphology). Delft3D can also be used operationally e.g. storm, surge and algal bloom forecasting. 
 
On this discussion page you can post questions, research discussions or just share your experience about modelling coastal and/or estuarine systems with Delft3D FM. 
 

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Sub groups
D-Flow Flexible Mesh
DELWAQ
Cohesive sediments & muddy systems

 

 

Message Boards

Where is settling velocity included in vertical direction of transport eq.

GS
Gholamreza Shiravani, modified 6 Months ago.

Where is settling velocity included in vertical direction of transport eq.

Padawan Posts: 60 Join Date: 6/25/16 Recent Posts

Hi D3D-Delwaq community,

could you tell me, in which subroutine is the concentration (CONC) computed? In processes (waq_process) the CONC is a substance and other processes will be calculated through concentration. But which subroutin does compute the CONC? it comes from AD-transport equation. But which subroutine in waq_kernel is the transport equation for amass or CONC? 

GS
Gholamreza Shiravani, modified 6 Months ago.

RE: Where is settling velocity included in vertical direction of transport

Padawan Posts: 60 Join Date: 6/25/16 Recent Posts

Dear Delwaq users, I found the answer :). It is considered in  trase2.f (line 200-Downward advection) in waq_process.

AM
Arjen Markus, modified 6 Months ago.

RE: Where is settling velocity included in vertical direction of transport

Jedi Knight Posts: 223 Join Date: 1/26/11 Recent Posts

The strategy in DELWAQ is to compute the mass balance - everything is converted to mass fluxes, these are summed and then the concentration is calculated from the mass and the volume. This necessarily differs per integration option. I fyou want to know the details, have a look in the routines dlwqn* - these are the main routines for each integration option.

GS
Gholamreza Shiravani, modified 6 Months ago.

RE: Where is settling velocity included in vertical direction of transport

Padawan Posts: 60 Join Date: 6/25/16 Recent Posts

Thanks Arjen. In sedim.f, the sedimentation flux (line 179,180 and 338) is calculated from CONC results. But how sedimentation flux will change the CONC?

AM
Arjen Markus, modified 6 Months ago.

RE: Where is settling velocity included in vertical direction of transport

Jedi Knight Posts: 223 Join Date: 1/26/11 Recent Posts

That is done i the very same way as all other fluxes: DELWAQ keeps track of the influence a particular flux has on a substance via a table of "stoichiometric" coefficients. For suspended sediment two fluxes are important: a flux from the water phase to the bottom material and the vertical transport (sinking of the material). Both are stored in the PMSA array, but have a different character - determined by the process definition. The exchange of material from the water phase to the bottom is a regular flux and represented by two stoichiometric relations:

dMwater/dt = - sedimentation flux

dMbottom/dt = + sedimentation flux

(Note: M is the mass in the segment)

For the sinking the flux as calculated is interpreted as a "flow velocity" on top of the flow prescribed by the hydrodynamics.