lift force calculation

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Paul Brss
Posts: 32
Joined: Mon Dec 04, 2017 3:00 pm

Re: lift force calculation

Post by Paul Brss »

Hi Yan,

Thanks for the tutorial on paraview. Yet, I think it takes a lot of time, in comparison with the subroutines I mean.

The cs_user_extra_operations-global_efforts.f90 subroutine will give you the force on the x, y and z axis. I might be wrong, but the function field_get_val_v(iforbr, bfprp_for) gets the efforts on the cells of the surface of your structure. Then the subroutines sums these values on the whole structure.

In order to obtain the hydrodynamic coefficients c_i, you need to calculate them. (I can't write formula properly but I think you know them. )

c_i = \frac{2*F_i}{\rho S v^2} with i=x,y,z ; F_i = hydrodynamic forces ; S = the caractistic surface ; v = caracteristic velocity

Best regards,

Paul
Paul Brss
Posts: 32
Joined: Mon Dec 04, 2017 3:00 pm

Re: lift force calculation

Post by Paul Brss »

Hi Luciano,

Thanks for your help !
Quick question you might answer: Is the option "no wall function" still available when using SST kw model ?
I can't choose it when using the GUI. I didn't try without.


Best regard


Luciano Garelli wrote: Fri Apr 13, 2018 4:43 pm Hello,

Here you can check the wall function options for the turbulence

https://www.code-saturne.org/cms/sites ... 9ec058107

Also I think that it is important to check the turbulent viscosity added by the turbulence method and the yplus.

Regards,
Luciano
yany
Posts: 60
Joined: Fri Aug 04, 2017 11:02 pm

Re: lift force calculation

Post by yany »

Hello Paul,

Yes, you're right. The value is force from the subroutine. I got the same problem with you. The value of drag is much higher than experiments. I used LES(wale).

All the best, Yan.



Paul Brss wrote: Tue Apr 17, 2018 8:56 am Hi Yan,

Thanks for the tutorial on paraview. Yet, I think it takes a lot of time, in comparison with the subroutines I mean.

The cs_user_extra_operations-global_efforts.f90 subroutine will give you the force on the x, y and z axis. I might be wrong, but the function field_get_val_v(iforbr, bfprp_for) gets the efforts on the cells of the surface of your structure. Then the subroutines sums these values on the whole structure.

In order to obtain the hydrodynamic coefficients c_i, you need to calculate them. (I can't write formula properly but I think you know them. )

c_i = \frac{2*F_i}{\rho S v^2} with i=x,y,z ; F_i = hydrodynamic forces ; S = the caractistic surface ; v = caracteristic velocity

Best regards,

Paul
attene
Posts: 68
Joined: Fri Jun 29, 2018 10:54 am

Re: lift force calculation

Post by attene »

Paul Brss wrote: Tue Apr 17, 2018 9:00 am Hi Luciano,

Thanks for your help !
Quick question you might answer: Is the option "no wall function" still available when using SST kw model ?
I can't choose it when using the GUI. I didn't try without.


Best regard


Luciano Garelli wrote: Fri Apr 13, 2018 4:43 pm Hello,

Here you can check the wall function options for the turbulence

https://www.code-saturne.org/cms/sites ... 9ec058107

Also I think that it is important to check the turbulent viscosity added by the turbulence method and the yplus.

Regards,
Luciano
Hello,

Did you solve this problem? I am facing the same issue with kw-SST ( I cannot select "no wall function" in the advanced options ). I am trying to figure out a way through the use of the subroutines...

Regards,

FA
Luciano Garelli
Posts: 280
Joined: Fri Dec 04, 2015 1:42 pm

Re: lift force calculation

Post by Luciano Garelli »

Hello,

What version are you using?

In version 5.0.8 when you open the "advanced options" in the turbulence model and select "No wall function" and save it, the value in the xml file is set to "0". But if you open it again the "2 scale model" appear like if the option has not been saved (May be a GUI issue).

Also you can check the value of iwallf in the setup file.
sst.png
Regards,

Luciano
attene
Posts: 68
Joined: Fri Jun 29, 2018 10:54 am

Re: lift force calculation

Post by attene »

Hi Luciano,


thanks a lot for your answer!
I am using the version 5.0.8 and indeed iwallf was 0 in the setup.log.

Regards,

FA
Yvan Fournier
Posts: 4070
Joined: Mon Feb 20, 2012 3:25 pm

Re: lift force calculation

Post by Yvan Fournier »

Hello,

The behavior Luciano explained (with the GUI resetting the wall function value when visiting it) was a bug. I just fixed it an will push the fix on the master branch (and possibly merge it on branches for 5.2.1, 5.1.6, and 5.0.10) by Monday.

For similar cases, do not hesitate to use the bug-tracker (not necessary for this one as I fixed it, but I may miss other details in some conversations I don't need to handle).

Best regards,

Yvan
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