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Re: lift force calculation
Posted: Tue Apr 17, 2018 8:56 am
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
Re: lift force calculation
Posted: Tue Apr 17, 2018 9:00 am
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
Re: lift force calculation
Posted: Tue Apr 17, 2018 11:24 am
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
Re: lift force calculation
Posted: Fri Sep 28, 2018 1:36 pm
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
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
Re: lift force calculation
Posted: Fri Sep 28, 2018 2:04 pm
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.
Regards,
Luciano
Re: lift force calculation
Posted: Fri Sep 28, 2018 2:44 pm
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
Re: lift force calculation
Posted: Sun Sep 30, 2018 12:31 am
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