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-   -   Wind Turbine Analysis Suggestion (http://www.cfd-online.com/Forums/openfoam/83793-wind-turbine-analysis-suggestion.html)

andrea.pasquali January 11, 2011 12:40

Wind Turbine Analysis Suggestion
 
Hi,
I'd like to investigate better the Wind Turbine Analysis problem.
Before considering this problem I did a transient analysis using dynamic mesh and ggi (just to do a test and to try the ggi) with a horizontal 3 blades turbine.
Then I read many treads and reports about this problem and I found some people suggest to use dynamic mesh, others to use MRF, other not, others to use SRF (for low rpm), other to use also rotation BC and others to use Body Force Model ... I'm a little bit confused...
Now I'm running the same turbine (same model and same setup) with MRF approach and it's giving me more or less the same torque (this is what I'm monitoring now).
But I'd like to investigate the problem more in detail. What I'd like to ask is:
Is it really correct use MRF for wind turbine? Maybe yes for Power result (considering my case) but for flow filed?
If I'd like to optimize the blade profile in order to obtain that one gives the best Power, can I use the MRF? (it will be very useful to reduce also the time of calculation).
But what I'm missing using MRF? Could I neglet it for my scope or are there other things I have to consider?
Otherwise, what is the correct method to do this in steady state? I don't want to do transient analysis.

Thanks for any suggestions

Andrea

maddalena January 12, 2011 03:26

Hi Andrea...
maybe you can find this article interesting: http://www.cd-adapco.com/press_room/...cs/23/mrf.html
Enjoy

mad

andrea.pasquali January 12, 2011 10:25

Hi Maddalena,
I got this article, I know it.
My torque with MRF approach is more or less the same with dynamic mesh.
I think I can use the MRF for my scope.

Thank you very much

Andrea

prashant.A January 12, 2011 13:30

Well, if this was a vertical axis turbine, the MRF results may be doubted against the transient moving mesh approach.
However, your problem (horizontal axis) defines well with steady MRF and as you have also observed Torque loading matches, I think its safe to go ahead with it

timo_IHS January 13, 2011 03:48

Hello Andrea,

if you have a big part of axial velocity in your rotating frame, you should use MRF, because it includes the velocity in absolute frame in the advection term and SRF only the velocity in rotating frame.

Greetz

andrea.pasquali January 17, 2011 17:39

1 Attachment(s)
Hi,
after tested (well) my 3 blades wind turbine MRF vs Dynamic Mesh, I'm testing a sector of it with MRF and periodic BC (cyclic).
I modeled just 1 blade in a 120 sector. The side faces are cyclic.
What I can see now is two things:
First, 1 blade gives me less than 3 blades / 3 torque (but maybe this is due by the mesh resolution that is not good). I'll refine my model and test it again;
Second, more strange, you can see the picture attached (in red): at the end of cyclic patch I have a strange velocity field! Also this is due by the mesh resolution? Or by cyclic BC? I'm missing something in my setup?

Thanks for any help

Andrea

s.q May 20, 2013 19:12

Quote:

Originally Posted by andrea.pasquali (Post 290027)
Hi,
I'd like to investigate better the Wind Turbine Analysis problem.
Before considering this problem I did a transient analysis using dynamic mesh and ggi (just to do a test and to try the ggi) with a horizontal 3 blades turbine.
Then I read many treads and reports about this problem and I found some people suggest to use dynamic mesh, others to use MRF, other not, others to use SRF (for low rpm), other to use also rotation BC and others to use Body Force Model ... I'm a little bit confused...
Now I'm running the same turbine (same model and same setup) with MRF approach and it's giving me more or less the same torque (this is what I'm monitoring now).
But I'd like to investigate the problem more in detail. What I'd like to ask is:
Is it really correct use MRF for wind turbine? Maybe yes for Power result (considering my case) but for flow filed?
If I'd like to optimize the blade profile in order to obtain that one gives the best Power, can I use the MRF? (it will be very useful to reduce also the time of calculation).
But what I'm missing using MRF? Could I neglet it for my scope or are there other things I have to consider?
Otherwise, what is the correct method to do this in steady state? I don't want to do transient analysis.

Thanks for any suggestions

Andrea


hi dear andrea
would you plz tell me how to use SRF in low speed wind turbines.
i,m simulating a wind turbine using fluent and its rotational speed is 12.1 rpm.

niloogh May 28, 2013 07:33

Quote:

Originally Posted by andrea.pasquali (Post 290843)
Hi,
after tested (well) my 3 blades wind turbine MRF vs Dynamic Mesh, I'm testing a sector of it with MRF and periodic BC (cyclic).
I modeled just 1 blade in a 120 sector. The side faces are cyclic.
What I can see now is two things:
First, 1 blade gives me less than 3 blades / 3 torque (but maybe this is due by the mesh resolution that is not good). I'll refine my model and test it again;
Second, more strange, you can see the picture attached (in red): at the end of cyclic patch I have a strange velocity field! Also this is due by the mesh resolution? Or by cyclic BC? I'm missing something in my setup?

Thanks for any help

Andrea

hi andrea
i had simulated a wind turbine such as you.
i,m calculating the output power using torque amounts by"report-moment..."
but the power output calculated in this way is 10 times bigger than the real amounts:confused:


what can i do???
would you plz help me???

andrea.pasquali May 28, 2013 08:08

Hi,
@ s.q. : I would use MRF
@ niloogh : What force library are you using? I used force lib and I got good results

Andrea

niloogh May 28, 2013 08:21

Quote:

Originally Posted by andrea.pasquali (Post 430489)
Hi,
@ s.q. : I would use MRF
@ niloogh : What force library are you using? I used force lib and I got good results

Andrea


tnx adrea
what did you mean by "force library " and "force lib"????

andrea.pasquali May 28, 2013 08:51

I used the force function into controlDict file.
Something like this:

functions
(

forces
{
type forces;
enabled true;
functionObjectLibs ( "libforces.so" );
outputControl timeStep;
outputInterval 1;
log true;
patches ( consoleFluid ); // name of the patch where you want calculate the forces
pName p;
*** UName*U;
//directForceDensity true;
//fDName fDMean;
CofR (0.625e-3 0 -1); // Center of Rotation
rhoName rhoInf;
rhoInf 1000; // fluid density
}

);

Ruli January 24, 2014 06:50

Quote:

Originally Posted by andrea.pasquali (Post 290843)
Second, more strange, you can see the picture attached (in red): at the end of cyclic patch I have a strange velocity field! Also this is due by the mesh resolution? Or by cyclic BC? I'm missing something in my setup?

Hi Andrea,
I suppose, that in these corners the aspect ratio of the cells could be too high. How does the mesh look there?

Best regards
Julian

be_inspired March 25, 2015 05:53

Quote:

Originally Posted by andrea.pasquali (Post 290027)
Hi,
I'd like to investigate better the Wind Turbine Analysis problem.
Before considering this problem I did a transient analysis using dynamic mesh and ggi (just to do a test and to try the ggi) with a horizontal 3 blades turbine.
Then I read many treads and reports about this problem and I found some people suggest to use dynamic mesh, others to use MRF, other not, others to use SRF (for low rpm), other to use also rotation BC and others to use Body Force Model ... I'm a little bit confused...
Now I'm running the same turbine (same model and same setup) with MRF approach and it's giving me more or less the same torque (this is what I'm monitoring now).
But I'd like to investigate the problem more in detail. What I'd like to ask is:
Is it really correct use MRF for wind turbine? Maybe yes for Power result (considering my case) but for flow filed?
If I'd like to optimize the blade profile in order to obtain that one gives the best Power, can I use the MRF? (it will be very useful to reduce also the time of calculation).
But what I'm missing using MRF? Could I neglet it for my scope or are there other things I have to consider?
Otherwise, what is the correct method to do this in steady state? I don't want to do transient analysis.

Thanks for any suggestions

Andrea

What solver did you use for dynamic mesh? pimpleDyMFoam or other?
I am trying to simulate a wind turbine also but because refinenement in the boundary layer and trailing edge, the time step should be quite small to achieve a maximum CFL=1.

andrea.pasquali March 25, 2015 06:27

Hi,
it was a very old project with a very old OF-extend version to use GGI. The solver was "turbDyMFoam" that in the newer releases is called "piso".
Using "pimple" you could allow a Courant Number grater than 1, I would say until 10.
Andrea


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