CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

is there any method give node based velocity BC?

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

LinkBack Thread Tools Search this Thread Display Modes
Old   July 18, 2006, 01:23
Default is there any method give node based velocity BC?
Posts: n/a
Dear all: I want to give a velocity inlet boundary condition by using UDF. As I have read, the velocity profile is given by F_Profile macro. So it is based on the face centroid corridnate. When I export the inlet velocity profile, I found the velocity is not as I want at the edge. I think it is because the Fluent software do interpolation process there, Is there any method which can give node-based velocity profile, So we can avoid the shift on edge.

The problem is u=1.5(y^2-2y+1) the velocity u at y=0 and y=1 should be 0. but in fact, when I use the follwing UDF.Afterig 1 step iteration, I export the inlet velocity profile and found the velcoity u is not 0 at y=0 and y=1. {... F_CENTROID(x,f,thread); y=x[1]; F_PROFILE(f,thread,position)=1.5*(y*y-2*y+1); ...}

  Reply With Quote

Old   July 18, 2006, 09:15
Default Re: is there any method give node based velocity B
Posts: n/a

Have a look at the UDF manual about how to define a velocity profile (I think in the section "sample problems").

If you really want this mathematical perfection, refine the mesh at the edges. But is it really indispensable to get this perfection to obtain reliable results ??????

I think you simply lose time in details.....

  Reply With Quote

Old   July 18, 2006, 21:21
Default Re: is there any method give node based velocity B
Posts: n/a
Dear Fab: Thanks for your suggestion! I have looked the section you mentioned. In fact, I think I use the ame method to define the velocity profile as the example, just use different maths function. When I plot the velocity profile at the inlet boundary, I find the velocity magnitude is what I wanted, but the X-velocity is differnet at the edge (seems to be explotated from inside). Whereas, in the boundary definition interface, I choose "component" method and just specify x-velocity using UDF, Y-velocity keeps to be 0.

What's wrong with it?

Thanks again! Regards!
  Reply With Quote


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
help with UDF for contact angle based on contact line velocity gandesk Fluent UDF and Scheme Programming 14 October 29, 2012 13:58
adapt viscous resistance based on velocity / UDF Häwimeddel FLUENT 2 April 20, 2009 10:08
Turbulence Production Based on the Curl of the Velocity Field ngj OpenFOAM Running, Solving & CFD 0 April 4, 2008 05:22
how to set velocity on node tipakorn Siemens 3 January 23, 2008 05:05
Terrible Mistake In Fluid Dynamics History Abhi Main CFD Forum 12 July 8, 2002 09:11

All times are GMT -4. The time now is 09:21.