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How to calcule the Drag Coefficient and Rotating Cylinder
Posted: Mon Mar 19, 2012 11:39 am
by Renan Neves Nascimento
Hi,
I wanna know what do I need to do to obtain the Drag Coefficient using Code Saturne (using Salomé to do the mesh)
Also, I'd like to know how can I simulate a rotating cylinder in the Code Saturne.
Thanks in advance.
Renan Neves Nascimento
Re: How to calcule the Drag Coefficient and Rotating Cylinder
Posted: Mon Mar 19, 2012 3:04 pm
by James McNaughton
What version do you use?
Re: How to calcule the Drag Coefficient and Rotating Cylinder
Posted: Wed Mar 21, 2012 11:37 am
by Renan Neves Nascimento
James,
I use the version 2.0.4
Re: How to calcule the Drag Coefficient and Rotating Cylinde
Posted: Wed Mar 21, 2012 3:57 pm
by James McNaughton
The following is what I do for my rotating cylinder case you'll need to tweak it I guess. There are other ways to do this too but it works for me :)
In usclim:
Code: Select all
alpha = 10.0d0 ! non dim rotation rate = omega*cyl_radius/U
! --- Cylinder (walls)
call getfbr('BODY', nlelt, lstelt)
!==========
do ilelt = 1, nlelt
ifac = lstelt(ilelt)
iphas = 1
itypfb(ifac,iphas) = iparoi
xx = cdgfbo(1,ifac)
yy = cdgfbo(3,ifac)
theta = atan(abs(yy/xx))
if(xx.ge.0.d0.and.yy.ge.0.d0) theta = theta
if(xx.lt.0.d0.and.yy.ge.0.d0) theta = - theta + pi
if(xx.lt.0.d0.and.yy.lt.0.d0) theta = theta + pi
if(xx.ge.0.d0.and.yy.lt.0.d0) theta = - theta + 2.d0*pi
ctheta = cos(theta)
stheta = sin(theta)
rcodcl(ifac, iu(iphas), 1) = alpha*(ctheta - stheta)
rcodcl(ifac, iv(iphas), 1) = 0.d0
rcodcl(ifac, iw(iphas), 1) = alpha*(stheta + ctheta)
enddo
The drag's an example in usproj and been discussed loads on this board (search for
efforts).
Eg:
Code: Select all
!initialise
do ii=1,ndim
xfor(ii) = 0.d0
enddo
call getfbr('BODY',nlelt,lstelt)
! ======
do ilelt = 1, nlelt
ifac = lstelt(ilelt)
! xfor is force in ii direction
do ii=1,ndim
xfor(ii) = xfor(ii) + ra(iforbr + (ifac-1)*ndim + ii-1)
enddo
enddo
!sum in parallel
if (irangp.ge.0) then
call parrsm(ndim,xfor)
endif
Hope that helps.
James
Re: How to calcule the Drag Coefficient and Rotating Cylinder
Posted: Thu Mar 22, 2012 12:22 am
by Renan Neves Nascimento
I'll try it!
Thank you, James!
Re: How to calcule the Drag Coefficient and Rotating Cylinder
Posted: Tue Apr 03, 2012 4:53 pm
by Guillaume Mercier
Hi James,
For your information, it exist in Fortran a function called "atan2" which does the job you've done with 4 lines.
atan2(x,y) gives you the argument of the complexe x+iy
not crucial but helpful,
Cheers,
Guillaume