Morphological Model Setup  Tidal Flats  Delwaq  Delft3D
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DELWAQDELWAQ is the engine of the DWater Quality and DEcology programmes of the Delft3D suite. It is based on a rich library from which relevant substances and processes can be selected to quickly put water and sediment quality models together. The processes library covers many aspects of water quality and ecology, from basic tracers, dissolved oxygen, nutrients, organic matter, inorganic suspended matter, heavy metals, bacteria and organic micropollutants, to complex algae and macrophyte dynamics. High performance solvers enable the simulation of long periods, often required to capture the full cycles of the processes being modelled. The finite volume approach underlying DELWAQ allows it to be coupled to both the structured grid hydrodynamics of the current Delft3DFLOW engine and the upcoming DFlow Flexible Mesh engine (1D2D3D) of the Delft3D Flexible Mesh Suite (or even other models such as TELEMAC). 'DELWAQ in open source' is our invitation to all leading experts to collaborate in further development and research in the field of water quality, ecology and morphology using Delft3D. Feel free to post your DELWAQ related questions or comments in this dedicated forum space. If you are new to DELWAQ, the tutorial (in the user manual) is a good place to start. A list of DELWAQ related publications is available here. ** PLEASE TAG YOUR POST! **  Sub groups

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Morphological Model Setup  Tidal Flats
Oliver Lojek, modified 7 Years ago.
Morphological Model Setup  Tidal Flats
Jedi Knight Posts: 111 Join Date: 4/30/13 Recent PostsI am setting up a model to simulate morphological long term processes.
Currently I am looking at detailed meshing of tidal channels which end within the domain. Does anybody have any suggestions on how to mesh this?
Kind regards,
Oliver
Qinghua Ye, modified 7 Years ago.
RE: Morphological Model Setup  Tidal Flats
Jedi Council Member Posts: 612 Join Date: 3/2/11 Recent PostsLooks like the area you are interested in has a tidal channel flowing in the area in an angle.
I would suggest a model covering bigger area first. Then you may nest the smaller model to get correct boundary conditions. You may have to tune the model very careful about sediment transport at very shallow water.... The Flooding scheme is definitely sth you should try. Maybe also cutting cell technique.
Regards,
Qinghua
Oliver Lojek, modified 7 Years ago.
RE: Morphological Model Setup  Tidal Flats
Jedi Knight Posts: 111 Join Date: 4/30/13 Recent Postsyou are correct, there is a tidal channel flowing through my area of interest.
However, I need to get the model to run properly first before I can add Sediment and so on  currently I seem to get a lot of CFL related issues.
I have removed all physical processes and so far just have a tidal boundary forcing and that is it. I am modelling one week which takes about 2 minutes on my small server.
The GUI suggested that the resolution was fairly high and the aspect ratio was fine as was the orthogonality. At some point however the Model seems to become instable and suggests Time steps of 0.147E01 Minutes.
I reduced the timestep from 5 min to 2.5, 1, 0.5 and 0.25 min. This usually happens around 80 to 90 % of the calculation.
*** MESSAGE Using UNESCO density formulation by default  
*** MESSAGE Momentum solver cyclic method is specified  
*** MESSAGE DRYFLP and DPSOPT both specified in MDfile. Using DPSOPT: MAX  
*** MESSAGE Transport solver cyclicmethod method is specified  
*** WARNING File will not be created  Inconsistent comm. file times  
*** MESSAGE Nodal factors updated at 20070101 00:00:30.0000  
*** MESSAGE Courant number for Uvelocity in Upoint equals 1.04 for (m,n,k) = (1,21,1), at nst = 10. Advised time step: 0.966E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Upoint equals 1.08 for (m,n,k) = (1,21,1), at nst = 11. Advised time step: 0.928E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Vpoint equals 1.02 for (m,n,k) = (2,20,1), at nst = 11. Advised time step: .980E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Upoint equals 1.18 for (m,n,k) = (2,17,7), at nst = 11. Advised time step: 0.848E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Vpoint equals 1.10 for (m,n,k) = (3,16,7), at nst = 11. Advised time step: .913E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Upoint equals 1.16 for (m,n,k) = (1,21,1), at nst = 12. Advised time step: 0.859E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Vpoint equals 1.12 for (m,n,k) = (3,16,7), at nst = 12. Advised time step: .896E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Upoint equals 1.40 for (m,n,k) = (2,18,9), at nst = 12. Advised time step: 0.713E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Vpoint equals 1.24 for (m,n,k) = (3,16,8), at nst = 12. Advised time step: .807E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Upoint equals 1.29 for (m,n,k) = (2,16,8), at nst = 13. Advised time step: 0.775E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Vpoint equals 1.24 for (m,n,k) = (3,16,7), at nst = 13. Advised time step: .806E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Upoint equals 1.37 for (m,n,k) = (2,16,9), at nst = 13. Advised time step: 0.729E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Vpoint equals 1.32 for (m,n,k) = (3,15,1), at nst = 13. Advised time step: .758E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Upoint equals 1.33 for (m,n,k) = (3,16,1), at nst = 14. Advised time step: 0.754E+00 minutes.  
*** MESSAGE Courant number for Uvelocity in Vpoint equals 1.28 for (m,n,k) = (3,15,1), at nst = 14. Advised time step: .780E+00 minutes. 
I have simulated waves with a 3G spectral model coupled to it on unstructured grids and unfortunately am not too familiar with curvilinear grids  are there any help resources for Delft3d on how to generate an appropriate mesh?
Attachments:
Oliver Lojek, modified 7 Years ago.
RE: Morphological Model Setup  Tidal Flats
Jedi Knight Posts: 111 Join Date: 4/30/13 Recent PostsDoes this routine only support a limited number of interpolated points aka. did I set the resolution too high for it to work recursively?
Kind regards,
Oliver
Oliver Lojek, modified 7 Years ago.
RE: Morphological Model Setup  Tidal Flats
Jedi Knight Posts: 111 Join Date: 4/30/13 Recent PostsFor the homogeneously fine grid I got the following values.
Thus the grid comprises 235 X 91 = 21'385 Cells  I usually introduce 10 vertical layers given a typical water level of about 4 m. Eventually it holds 213'850 Cells to be calculated per step.
Reading the manual and the modelling guidelines I found that a typical grid comprises 20'000 cells. Therefore, I guess I will have to coarsen the grid quite a bit and add some nesting for the area of interest as suggested by Qinghua earlier.
Interpolation Check by Reverse Interpolation
*************************************************
Mean Interpolation Error : 0.823365E01 [m]
Mean Abs Interpolation Error : 0.365152E+00 [m]
Maximum Error Value : 0.528059E+03 [m]
Number of Samples Checked : 80615 []
Actual and Maximum Dimensions of Data
****************************************************************
Data Type : Actual Maximum
Grid MDirection : 235 235
Grid NDirection : 91 91
Samples : 102370 102445
Land Boundary : 0 1
Polygon : 0 1
Depth Points in Polygon : 21381 21385
Second Depth Points in Polygon : 0 21385
Samples in Polygon : 102370 102445
Volumes and Areas below Reference Level
*************************************************
Volume Grid below 0.0[m]: 4.578562E+08[m3]
Grid Area below 0.0[m]: 1.368022E+08[m2]
Polygon Area : 0.000000E+00[m2]
Dmitry Kushnir, modified 7 Years ago.
RE: Morphological Model Setup  Tidal Flats
Jedi Knight Posts: 107 Join Date: 11/9/12 Recent PostsI think that modeling guide about computational grid refer to 20'000 cells per one layer. I'm now running simulations on a domain consisting of 244x52 grid cells and with 15 sigmalayers this will be similar to your model. For now it was running without errors. Probably you don't need to coarse your grid. Have you tried to check the courant number in quickin for your bathymetry and time step?
Regards,
Dmitry
Oliver Lojek, modified 7 Years ago.
RE: Morphological Model Setup  Tidal Flats (Answer)
Jedi Knight Posts: 111 Join Date: 4/30/13 Recent Postsgood to know  I was wondering already seemed way to small.
I had the model running but it gave me multiple errors on too harsh velocity changes. I checked the courant numbers but QUICKIN suggested negative values.
e.G.:
*** WARNING Velocity change too high > 5.00 m/s (per 0.5 DT) after 18020
*** timesteps in the following points:
*** WARNING Velocity change too high > 5.00 m/s (per 0.5 DT) after 18021
That is why I assumed I better coarsen the grid a bit. I did coarsen it and othogonalized it and checked the triangulation and so forth  now I get courant numbers around 0.276 all over the domain (see PNG).
I'll reduce the runtime and see if the inconsistencies are gone.
Regards,
Oliver
Attachments:
Qinghua Ye, modified 7 Years ago.
RE: Morphological Model Setup  Tidal Flats
Jedi Council Member Posts: 612 Join Date: 3/2/11 Recent PostsYes, I would say to decrease the time step, to make the grid coarser, or to increase the grid orthogonality, and so on, could be helpful to remove the warning about the big water level gradient and velocity gradient.
Delft3D used a lot of numerical tips to stabilize the solution. Officially the Cr number can be as big as 10. I would not trust the results if the Cr number is bigger than that.
But there is no general solution to solve everybody's modeling problem. So in that sense, we still have to tune the model and modelling stays as an art. The modeller stays as artists.
Keep us update and see what comes out of your work as an artist...
Regards,
Qinghua
Oliver Lojek, modified 7 Years ago.
RE: Morphological Model Setup  Tidal Flats
Jedi Knight Posts: 111 Join Date: 4/30/13 Recent Postsit worked  the model runs smoothly and the output looks quite good.
Regards,
Oliver
Oliver Lojek, modified 7 Years ago.
Morphological Model Setup  Tidal Flats  Domain size
Jedi Knight Posts: 111 Join Date: 4/30/13 Recent PostsGiven is fine, noncohesive sediment < 63 µm comprise between 100  70 % of sediment probes taken on site.
Average water level amounts to 5.00 m with a tidal amplitude of 2.75 m.
Current velocities range between 0.3  1.0 m/s within the domain over the tide.
Regards,
Oliver
Qinghua Ye, modified 7 Years ago.
RE: Morphological Model Setup  Tidal Flats  Domain size
Jedi Council Member Posts: 612 Join Date: 3/2/11 Recent PostsI would say it should be ok, but still depends on the situation.
Regards,
Qinghua
Oliver Lojek, modified 7 Years ago.
Morphological Model Setup  Area of Interest
Jedi Knight Posts: 111 Join Date: 4/30/13 Recent PostsI am progressing on the model and started looking at the NESTING possibilities for the Model.
I have supplemental high resolution bathymetry data for the area of interest in my domain.
Currently I am a little puzzled as to how one could mesh it in order for it to work smoothly.
I attached an overview of the area. It features a coastline with artificial structures and adjacent tidal flats.
I am thankful for suggestions on how to mesh this the best possible way.
Cheers,
Oliver