open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

Am currently working on a model which includes culverts.

As part of the study I am investigating the influence of the culverts on water exchange which is modelled using a conservative tracer. My understanding is that the culverts would conserve the tracer mass, however, I can clearly see in the results that transport of the tracer between the source and sink sides of the culvert is not working correctly. It seems that the source of the culvert has a difference tracer concentration to the sink side.

As you can see in the attached figures, tracer is initialized to a value of 100 on either side of the culvert. A few time steps later, the tracer concentration is significantly reduced suggesting that the culvert source has a tracer concentration below 100 (perhaps 0).

Has anybody experienced this before?

Many thanks,
Toby

Hi Toby
I agree that culverts should conserve tracer and in your case it's not seems to be the case...
I have in mind a case where we had problems with the tracer numbering dur to a bug few years ago.
For me this was corrected but maybe you use an old version?
By the way, you could easily check by using 2 tracers (one with 100, the second with 200) and see if the problem exists for both...

Hope this helps

Hi Christophe,

Thanks for the quick response. I'm currently on the latest V8P4 version so that shouldn't be an issue. I am however using a computation restart file to initialize the tracer concentration so am wondering if this has anything to do with it.

Will try to include another tracer over the same area but different number to see if that resolves the issue.

Thanks,
Toby

Hi Christophe,

Changing the tracer number doesn't seem to influence the results. In this case I modelled the same initial tracer concentration but using TR3 instead of TR1. Am trying to write the tracer concentration outputs for one of these culvert nodes to understand what is going on.

Regards,
Toby

So have spent the day trying to debug the issue inside BUSE and DIFSOU but cannot figure out what is going on.

Have confirmed that all I1 and I2 nodes are correct etc. I've attached my .CAS file and culverts file for further debugging if anyone is interested in taking a look. Unfortunately I need to deliver this study quite soon and wasn't expecting to run into something like this.

If anyone has a clue what might be going on would be really much appreciated if you could reach out to me.

Many thanks,
Toby

Did you tried with option for culvert 1?
You confirm the discharge computation is OK?

Hi Christophe,

Will run a test with Opt 1 but the computed flows with Opt 2 appear to be correct. Attached is a timeseries of TELEMAC computed total flow rates (summed over all culverts) through the causeway section previously shown.

Also shown is the total flow rate estimated using the same Bodhaine eqns. but using water levels extracted from a model run excluding the culverts. I attribute the reduction in computed flow due to the likely reduction in head once the culverts are in place.

Will get back to you once I have some results with Opt 1.

Regards,

Thanks for the clarifications.
According to these results, I agree switching to opt 1 will not solve the problem
Maybe a final test could be to run in sequential rather in parallel

Regards

Unfortunately sequential doesn't change the results either.

Been using single core while trying to debug the issue today.

And with a limited number of culvert?