CFD Online Logo CFD Online URL
Home > Forums > FLUENT

strange node values @ solid/fluid interface - help

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

LinkBack Thread Tools Display Modes
Old   October 27, 2008, 12:38
Default strange node values @ solid/fluid interface - help
Posts: n/a
Hey guys,

I'm modeling a heat sink (HS) operating in natural convection. Here is an overview of the model:

Geo + mesh: - one solid volume (al.), - one fluid volume (air), - hex elements in the solid, - tet elements in the fluid, - non-conformal interface between HS and Ambient Air (AA), - heat source at the bottom of the heat sink. - pressure outlet/walls/symetries to close my model (with correct backflow temp.)

Solver set-up: - laminar model, - gradient option: Green-Gauss node-based, - density: boussinesq model (-> steady state), - pressure disc.: body force weighted, - momentum/energy disc.: 2nd order upwind. (all other parameters left to default setup)

First of all, do you see some nonsense in my setup?

Here is my problem:

The 1st run used a quite coarse mesh, and gave a physically realistic solution. When plotting the temperature contours at the HS/AA interface, the facet contour looked great, and the node values contour looked a bit more 'random', but only oscilating by +/- 1 deg.C around facet values. so I thought: no big deal, this might be due to the non conformal interface, let's run the same simulation with a finer mesh and see what happens...

So I ran a second model, with the same setup but a finer mesh. The facet values were still very realistic, but this time, some nodal values on the interface are totally unrealistic (2 nodes in the same cell with a temperature difference of 400K !?)

From Fluent help files, I read that the node values are interpolated from neighbor cell values. But my cell values look ok (no crazy values when reporting min/max temp in the volumes). So what's happening? Is it due to the non-conformal interface?

Another thought was: I'm using the node-based gradient method... so I guess If my node values are wrong, this could affect the validity of my solution? (not only a post-processing issue, if you see what I mean).

For info, the mesh refinement significantly increased the temperature of my heat source (+10%).

Fluent Gurus? Any clue?

Thanks a lot in advance! /JB
  Reply With Quote

Old   October 28, 2008, 07:18
Default Re: strange node values @ solid/fluid interface -
Posts: n/a
  Reply With Quote

Old   November 1, 2008, 13:04
Default Re: strange node values @ solid/fluid interface -
Posts: n/a
  Reply With Quote


Thread Tools
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 On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Fluid - Solid Domain Interface Daniel CFX 6 February 15, 2009 19:09
Interface Fluid/Fluid and Solid Thomas Vanneste FLUENT 0 December 16, 2008 04:40
Setting Roughness on a Solid-Fluid Interface JensonButton CFX 1 February 7, 2008 14:41
BC at the interface of the fluid and solid manohar CD-adapco 3 April 8, 2005 11:34
fluid solid interface Alex CFX 1 February 18, 2005 21:55

All times are GMT -4. The time now is 10:57.