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

GS
Gholamreza Shiravani, modified 13 Days ago.

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

Padawan Posts: 50 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 10 Days ago.

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

Padawan Posts: 50 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 10 Days ago.

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

Jedi Knight Posts: 215 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 10 Days ago.

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

Padawan Posts: 50 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 10 Days ago.

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

Jedi Knight Posts: 215 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.