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-   -   Problem in AMI (http://www.cfd-online.com/Forums/openfoam-solving/99921-problem-ami.html)

ysh1227 April 16, 2012 06:32

Problem in AMI
 
Hi, everyone.
I am new in OF and I study and simulate OF for two month. (OF 2.1.0)

I want to run the Small Horiziontal Axis Wind Tubine case including tower, so I chose pimpleDyMFoam as solver and kOmegaSST as turbulence model.

First, I ran the case without a tower to know the proper condition to simulate, but the result always diverged, increasing Courant Number and other things.

I decided to change the solver to MRFSimpleFoam. But I met the trouble that time step continuity error increase with the iterations.

I tried to find the reason and found that, in this forum, some people had the similar problem.
They had 0 value as AMI: patch source weights min, but I had about 0.1 value
Their solution is to adjust and improve the mesh.
So I adjusted the meshes(AMI) that had the odd values, but the results also became wrong and time step continuity error increase with time.

AMI: Patch source weights min/max/average = 0.679762, 1, 0.998602
AMI: Patch target weights min/max/average = 0.154367, 1, 0.998088

Before I adjusted the mesh, I tried a lot of things to solve the problem.
For example, I had changed fvScheme, fvSolution, time step, decomposePar method, initial condition, Patch type ..........
All of those are useless.

I have studies OF alone and there are no one who can know OF well.

Is there anyone who can advise me about simulation of wind turbine with OF?
AND I want to know the exact meaning of time step continuity error and AMI weight.

linnemann April 16, 2012 07:12

Hi

You can use this as an example.

http://dl.dropbox.com/u/15968063/3DStruct.TSR1.0.tar.gz

That is a 3bladed VAWT with a NACA0012 profile.

Its done using 1.6-ext but you can change the GGI to AMI and it should work with 2.1. Also I was using transientSimpleDyMFoam and not pimpleDyMFoam.

Also you can't use MRF for a VAWT. When the MRF zone is perpendicular to the flow is generates flow that looks like flow over a cylinder. I cant go into the specifics about this other than tell you that it wont work. The same problem exists in Fluent.

ysh1227 April 16, 2012 07:19

Thanks, Linnemann. :)
I will check the example of VAWT right now.

hum..I have another question.
Do you know the specific means about AMI weights and time step continuity error?

linnemann April 16, 2012 07:36

The best thing you could was to upload the case as I've done with the VAWT case and have people have a look at the mesh/setup.

The continuity issues is often related to the mesh and fvSchemes/fvSolutions and BC's so in general it can be anything so it can be a hard one to track down with the little info you have given.

Following this guide will most likely get you more help.

http://www.cfd-online.com/Forums/ope...-get-help.html

ysh1227 April 16, 2012 07:51

Thank you :)
This is the first time to question on the web, so I'm sorry that I didn't give you the necessary info required to solve the trouble.

First, as I said, I'll check your case and my case again, and then I'll upload in the way you suggest.
I hope that I could learn more from you.

kid April 17, 2012 08:02

what is AMI and GGI ?
and what would be steps converting GGI blocks in file to AMI?

Some guidance plz.

regards

Santos-Dumont April 17, 2012 08:58

Thanks linnemann for sharing your case,

Unfortunately, I didn't succeed in running it. Would you give us a guidance to get it working with AMI or even in GGI or repost this case updated with AMI ??

Thanks,
Charles

linnemann April 17, 2012 09:57

Just unpack it and use it with OF1.6-ext pimpleDyMFoam solver or compile transientSimpleDyMFoam and use that.

A.Wendy March 11, 2013 10:26

Quote:

Originally Posted by linnemann (Post 355145)
Just unpack it and use it with OF1.6-ext pimpleDyMFoam solver or compile transientSimpleDyMFoam and use that.

hi,

i just tried to run this case and i get an floating point exception.
can this caused by a computer problem? i do not get it in my mind why on a different PC the calculation works but not ion mine. i get these error more often.


best wishes

Andy


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