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

Decay rate in PART program.

MS
Masaaki Sato, modified 6 Years ago.

Decay rate in PART program.

Youngling Posts: 2 Join Date: 8/8/14 Recent Posts
Hello all,

Using PART program (Delft3D ver. 4.01), I am simulating larval dispersal of reef fish.
In the model, I used some decay rates [0, 0.10, 0.20, 0.30, 0.40 (1/day)] as larval mortality to see its effect on particle (larval) retention within a study site after pelagic larval duration (8 days).
I expected the particle retention decrease with increasing decay rates, because total number of remaining particles must decrease with increasing decay rates.
However, there was no such a trend in simulation results of particle tracking.

So, I checked number of remaining particles on 1 day after release for each decay rate, but the number did not decrease with decay rates.

Following PART manual, I set decay rates at PROCESS PARAMETERS window when making an input file.
I want to know why decay rates does not affect number of particles in this setting. Any suggestions or answers would be appreciated for it.

Best regards,

Masaaki Sato
MJ
Michel Jeuken, modified 6 Years ago.

RE: Decay rate in PART program. (Answer)

Jedi Knight Posts: 154 Join Date: 1/21/13 Recent Posts
Dear Masaaki,

The decay rate does not affect the number of particles in your system, but the mass of each individual particle. A lower mass per particle should lead to lower concentrations.

best regards,
Michel
MS
Masaaki Sato, modified 6 Years ago.

RE: Decay rate in PART program.

Youngling Posts: 2 Join Date: 8/8/14 Recent Posts
Dear Michel,

Thank you for reply.
I understood the meaning of decay rate.

Best regards,

Masaaki
U
Jack Teo, modified 3 Years ago.

RE: Decay rate in PART program.

Hi Masaaki,

I find this strange too.

I did a test on decay rate in DELFT3D-FLOW and they use first order decay rate, just like how PART defined decay rate in their manual. However, when running model with a expected decay rate of 10% per day (which is 0.105/day), my oil particles decayed almost instantly.

Can anyone help us with this? Thanks.
MJ
Michel Jeuken, modified 3 Years ago.

RE: Decay rate in PART program.

Jedi Knight Posts: 154 Join Date: 1/21/13 Recent Posts
Are you sure the oil that this is cause by the decay? It could also be that the oil is dispersed in the water column. you could inspect the <oilname>.csv file for this. Also the out-file should tell you more about why your oil disappears.