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ketaki27

2D simulation run fails to begin

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Hi ,

 

I am running a TUFLOW 1D/2D model for a river with tributaries of order 3.

 

The model runs stably at timestep 0.2 when run in 1D domain alone and is free from any 2D file errors  or warnings but fails to start the simulation when linked with 2D domain.

 

Options tried :

 

1. Tried to reduce the initial conditions so that the initial stage is within the  banks

2. Tried increasing the dz value in _2d_Zsh_banks..file to increase the elevation at the banks ranging from values 0.1 to 1, the model did run for about 2% at dz value 0.8 but stopped after that.

3. Added different flag combinations for HX lines- such as '2', 'z' 's'.

 

None of the above trials have worked. My confusion is when the model runs in 1D domain, it has to run within the 2D domain also. Am using lidar data as grid to extract zpts with a resolution of about 2 m, hence used the cell size of 1m.

 

I have already crossed the deadline for project submission and really need help in this!

 

Anticipating a quick response

 

Regards,

ketaki

 

MB_WS_2D_UPDATED0_006.bmp

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Hi Ketaki,

 

Does the model fail to start the computations, or does the simulation go unstable shortly into the model?

 

The attached image seems to indicate that the model is an TUFLOW - ISIS (Flood Mapper) model, is this correct?

 

Are you able to email the TUFLOW log file (.tlf) through to support@tuflow.com and we can take a closer look.

 

Cheers

Phil

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Hi,

 

A couple of specific points:

1) It looks like your initial conditions (ICs) in ISIS are not quite consistent with your boundaries (hence the wobble at the start of outflow hydrograph shown in your bitmap); you might do well to extract ICs from about 0.75 hours where it's all smooth but still at low flows, and apply that at time zero. ISIS may be able to handle the jump at simulation start, but when also interacting with TUFLOW that may just be a bit much.

2) Yes, you'd do well to have your ICs low enough that there should be no exchange of flow between ISIS and TUFLOW at the start of the simulation. If you've got save maximums on in the .TCF and it achieves even a couple of timesteps before dying, you'll be able to pinpoint where there is interaction between the 1D and 2D; that's the place to be focussing on! I would advise against applying a widespread dz change of your banklines, as that's going to unrealistically affect results elsewhere in the model.

 

And more generally:

3) Do you have any boundaries attached to the 2D that are not linking with ISIS? i.e. an HT or HQ? If these are near to the HX boundaries linking to ISIS, then they'd need to be consistent with the 1D data (so if you've got a NCBDY with a gradient of 0.002 on it, then a nearby HQ in TUFLOW would benefit from also having an automatic 0.002 gradient applied; or an HTBDY in ISIS would need to be at similar (or the same) levels as a 2D HT in the vicinity.

4) All the usual guidance about stabilising 1D-2D models applies; not having a 1D channel that's "thin" compared to your 2D cells, using a 1D timestep that's half the size of your 2D timestep, and the 2D timestep (in seconds) no larger than half the cell size (in metres), etc.

 

If you can give any further detail about where it's failing (from point 2 above) there may be further advice to be offered.

 

Good luck!

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Hi Philip,

 

I have emailed the .tlf file at the given location. There are two .tlf files, one is the case where the model fails to start the computations and the other is where the model runs for 2% at dz=0.8

 

 yes, its TUFLOW-ISIS(Flood -Mapper) model.

 

Hope, this helps, and if required I can even send the model files.

 

Hi PHA,

 

Thanks for the various options, but I have tried them all, and still am unable to get the model to kick-off. :( The model ran for about 0.4 hours before it stopped.

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Hi All,

 

Thank you for the guidance. The 2D model is running in stable conditions. The issue was with initial stage going beyond the bank elevations at some Cross-sections. So extended the cross-section data, took care of the wobble at the initial time step =0, and it all works fine now :)

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On 2015-6-3 at 11:34 AM, ketaki27 said:

Hi ,

 

I am running a TUFLOW 1D/2D model for a river with tributaries of order 3.

 

The model runs stably at timestep 0.2 when run in 1D domain alone and is free from any 2D file errors  or warnings but fails to start the simulation when linked with 2D domain.

 

Options tried :

 

1. Tried to reduce the initial conditions so that the initial stage is within the  banks

2. Tried increasing the dz value in _2d_Zsh_banks..file to increase the elevation at the banks ranging from values 0.1 to 1, the model did run for about 2% at dz value 0.8 but stopped after that.

3. Added different flag combinations for HX lines- such as '2', 'z' 's'.

 

None of the above trials have worked. My confusion is when the model runs in 1D domain, it has to run within the 2D domain also. Am using lidar data as grid to extract zpts with a resolution of about 2 m, hence used the cell size of 1m.

 

I have already crossed the deadline for project submission and really need help in this!

 

Anticipating a quick response

 

Regards,

ketaki

 

MB_WS_2D_UPDATED0_006.bmp

Hi All,

I am also facing similar issue with 1D-2D linked model.

The model runs stably at timestep of 5sec when run in 1D domain alone and is free from any 2D file errors  or warnings but fails to start the simulation when linked with 2D domain.

Cell size used - 4m, 2D timestep - 5 sec

I have checked the intial stage at all cross-sections and it is within the banks.

Can you suggest some options to help with model run.

 

Regards,

Ankita

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