CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM

Cylindrical coordinate system - tangential velocity

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 6, 2010, 10:18
Default Cylindrical coordinate system - tangential velocity
  #1
Member
 
alessio.nz's Avatar
 
Alex
Join Date: Apr 2010
Posts: 48
Rep Power: 16
alessio.nz is on a distinguished road
hi,

I am running a case in which I have to set up the velocity in cylindrical coordinate system. My case has the axial velocity of 10 m/s and tangential velocity (which is homogeneous in all inlet) of 7 m/s (radial component is zero). With the script for the inlet velocity in the BC, I have the following possibility:

inlet
{
type cylindricalInletVelocity;
axialVelocity 10;
centre (0 0 0); //by default (0 0 0)
axis (0 0 1);
rpm 22.29;
radialVelocity 0;
value uniform (0 0 10);
}

but this script gives me only an outside tangential velocity (given by the rpm and the radius of the inlet tube) which is not the homogeneous tangential component I need for the simulation (in this case it is proportional to the radius, but this is not my case).

If I set

"tangentialVelocity"

is not recognized!

does anyone know how to solve this problem?

many thanks
alessio.nz is offline   Reply With Quote

Old   December 6, 2010, 21:39
Default
  #2
Member
 
Stefano Wahono
Join Date: Aug 2010
Location: Melbourne, Australia
Posts: 42
Rep Power: 16
swahono is on a distinguished road
I think you better of using groovyBC.

Download instruction from:
http://openfoamwiki.net/index.php/Contrib_groovyBC

The 0/U dict entry should look something like this:

Code:
inlet    {        type            groovyBC;        variables       "rpm=8000.0;Un=55.8;c=sum(pos()*mag(Sf()))/sum(mag(Sf()));n=sum(normal())/mag(sum(normal()));p=pos()-c;r=mag(p)+1.0e-10;R=max(r);xt=vector(n.y,-n.x,0);xT=xt/mag(xt);yt=vector(-n.x*n.z,-n.y*n.z,n.x*n.x+n.y*n.y);yT=yt/mag(yt);";        valueExpression "-Un*normal() + (rpm*pi/30)*((p & yT)*xT - (p & xT)*yT)";
c is the centre of the patch, n is the averaged patch normal. You can easily extend it to have a variation on the patch normal component, for instance a parabolic inlet would only require the addition of *(1-pow(r/R,2)) to Un*normal().

Cheers,
Stefano
swahono is offline   Reply With Quote

Old   December 7, 2010, 06:07
Default Re:
  #3
Member
 
alessio.nz's Avatar
 
Alex
Join Date: Apr 2010
Posts: 48
Rep Power: 16
alessio.nz is on a distinguished road
Thank you very much for your answer. I didn't know anything about groovy BC, which is actually always a usefull tool since I am new on OF.

My problem, unfortunately, is not regarding a swirling with rpm.

Imagine that I have a tube in which I want to set up a velocity in cylindrical coordinate with two components: an axial one and a tangential one. If I use rpm, the tangential velocity is proportional to radius, but in my case all the intel patch needs the same tangential component magnitude (see the inlet zone on the attachment). This is due to simulate the swirling motion.

Have a look to the picture of the inlet: setting up the axial and tangential component, inside the tube I will have a swirl.

Many thanks for cooperation

regards
Attached Images
File Type: png sim.png (12.7 KB, 90 views)
alessio.nz is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
cylindrical coordinate -Gambit noussa ANSYS Meshing & Geometry 2 June 12, 2010 10:07
velocity of massless particles and velocity of flow field in same coordinate payam_IUST FLUENT 0 October 19, 2009 00:24
Star-CD Cylindrical coordinate hamoudi STAR-CD 4 April 29, 2009 12:11
tangential velocity on a velocity inlet in 2D bretti FLUENT 0 July 3, 2007 09:42
Star-cd:Refine mesh in cylindrical coordinate system Moussa Diarra Main CFD Forum 0 May 11, 2000 09:17


All times are GMT -4. The time now is 18:57.