Parallel NS-kepsilon-HT: defect in velocity field
Parallel NS-kepsilon-HT: defect in velocity field
Hello,
I am running a Navier-Stokes simulation with k-epsilon turbulence model coupled with heat transfer equation. When I do a serial run everything is fine, however with parallel run I get strange results:
One symptom is the defects in the velocity field. These defects take place in the interfaces between two partitions (take a look at the attached picture)
Please advice.
Br,
Eelis
I am running a Navier-Stokes simulation with k-epsilon turbulence model coupled with heat transfer equation. When I do a serial run everything is fine, however with parallel run I get strange results:
One symptom is the defects in the velocity field. These defects take place in the interfaces between two partitions (take a look at the attached picture)
Please advice.
Br,
Eelis
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Re: Parallel NS-kepsilon-HT: defect in velocity field
Hi Eelis
The given equations are not the most robust in Elmer. Are you sure that you reach convergence i.e. the results are not from an unconverged state.
By the way, you might get a nicer partitioning using the dual graph in Metis, e.g.
-Peter
The given equations are not the most robust in Elmer. Are you sure that you reach convergence i.e. the results are not from an unconverged state.
By the way, you might get a nicer partitioning using the dual graph in Metis, e.g.
Code: Select all
-partdual -metis 64 4
Re: Parallel NS-kepsilon-HT: defect in velocity field
Hi Peter
The parallel run is working well when I use this dual graph.
Thank you!
-Eelis
The parallel run is working well when I use this dual graph.
Thank you!
-Eelis
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Re: Parallel NS-kepsilon-HT: defect in velocity field
Hi Eelis
The old partiotioning should have worked as well. There may be two reasons
1) The partitioning is such that the preconditioners don't work as well and you didn't actually get convergence and the results just shows this.
2) You did the convergence but there is a bug in the parallel implementation.
If the case is 2) it is a little bit alarming though you overcome it with better partitioning.
-Peter
The old partiotioning should have worked as well. There may be two reasons
1) The partitioning is such that the preconditioners don't work as well and you didn't actually get convergence and the results just shows this.
2) You did the convergence but there is a bug in the parallel implementation.
If the case is 2) it is a little bit alarming though you overcome it with better partitioning.
-Peter
Re: Parallel NS-kepsilon-HT: defect in velocity field
Hi Peter,
I checked it again, and the Navier-Stokes linear system has no problems to converge. A Bug then it is?
Please tell me how to proceed in finding the problem.
Cheers,
Eelis
I checked it again, and the Navier-Stokes linear system has no problems to converge. A Bug then it is?
Please tell me how to proceed in finding the problem.
Cheers,
Eelis
Re: Parallel NS-kepsilon-HT: defect in velocity field
Takala wrote:Hello,
I am running a Navier-Stokes simulation with k-epsilon turbulence model coupled with heat transfer equation. When I do a serial run everything is fine, however with parallel run I get strange results:
One symptom is the defects in the velocity field. These defects take place in the interfaces between two partitions (take a look at the attached picture)
Please advice.
Br,
Eelis
Hi,
I'm still experiencing this issue. Even if I don't have the K-epsilon equation.
Do you have any ideas how to track this?
Cheers,
Eelis
Re: Parallel NS-kepsilon-HT: defect in velocity field
Hello,
I think this problem has to do with the Result Output Solver:
I tested the Step_ke case from /tests and one can see the issue also there if Result output solver is used. However, in ep format there are no problems at all.
Edit. No it is not. Now I tested again with my own model and ep file has the problem as well....
Cheers,
Eelis
I think this problem has to do with the Result Output Solver:
I tested the Step_ke case from /tests and one can see the issue also there if Result output solver is used. However, in ep format there are no problems at all.
Edit. No it is not. Now I tested again with my own model and ep file has the problem as well....
Cheers,
Eelis
Re: Parallel NS-kepsilon-HT: defect in velocity field
some errors (see attached log) when trying to run parallel (NS-heat coupling).
Cheers,
Eelis
Cheers,
Eelis
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- log.txt
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Re: Parallel NS-kepsilon-HT: defect in velocity field
Hello,
I found the problem:
I used to use this command with ElmerGrid:
And it is faulty! Now I use these: first convert to serial run
Then do the partitioning by using the serial elmer mesh format
Cheers,
Eelis
I found the problem:
I used to use this command with ElmerGrid:
Code: Select all
ElmerGrid 8 2 file.unv -autoclean -metis 32 4 -partdual
Code: Select all
ElmerGrid 2 2 file.unv -autoclean
Code: Select all
ElmerGrid 2 2 file.unv -metis 32 4 -partdual
Eelis
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Re: Parallel NS-kepsilon-HT: defect in velocity field
Hi Eelis
Thanx for figuring that out! I will look at the problem time permitting.
-Peter
Thanx for figuring that out! I will look at the problem time permitting.
-Peter