Search found 63 matches
- 28 Apr 2011, 22:12
- Forum: ElmerSolver
- Topic: Cooling problem
- Replies: 27
- Views: 14981
Re: Cooling problem
Hi Juha, well, that body (the heatsink), should not be part of the air domain, but maybe I don't understand how to set up the model. Basically, I have a body that models the air, and for that I solve the heat equation as well as Navier-Stokes; all the other bodies (including the heatsink) are not fl...
- 28 Apr 2011, 21:11
- Forum: ElmerSolver
- Topic: Cooling problem
- Replies: 27
- Views: 14981
Re: Cooling problem
Hi Juha, the heatsink is body #2, name "HS_1", with this def: Body 2 Name = "HS_1" Equation = 1 Material = 1 Target Bodies(1) = 2 End Thanks for the clarification regarding the +/- rule. I'll have to re-run the system with all the boundaries between fluids and solids having a wal...
- 28 Apr 2011, 19:29
- Forum: ElmerSolver
- Topic: Cooling problem
- Replies: 27
- Views: 14981
Re: Cooling problem
There still seems to be something strange (if not wrong) with my model. I've added boundary conditions to each face between air and solids in my model, and now everything is much hotter than before (by about 70C). Moreover, if you look at this slice through the middle of the model (and through the h...
- 28 Apr 2011, 17:34
- Forum: ElmerSolver
- Topic: Cooling problem
- Replies: 27
- Views: 14981
Re: Cooling problem
Juha, thanks for the clarification. I understood your previous post to imply outwards -> inwards for plus. Having '+' in the direction of outward pointing normal makes sense.
Cheers,
Tibi
Cheers,
Tibi
- 28 Apr 2011, 16:57
- Forum: ElmerSolver
- Topic: Cooling problem
- Replies: 27
- Views: 14981
Re: Cooling problem
Hi Juha, thanks again for the information. However, I'm wondering whether it's always the case that a '+' is outwards->inwards. I'm attaching two images from Paraview showing the velocity vectors on a slice through the middle of the model. vel_vect_plus.jpg vel_vect_minus.jpg As you can see, in the ...
- 27 Apr 2011, 19:13
- Forum: ElmerSolver
- Topic: Cooling problem
- Replies: 27
- Views: 14981
Re: Cooling problem
Juha, thank you very much for your reply. I've updated the model with the correct speeds, but I still have some issues with air speed. Just as a clarification. When I set the air speed to a value (say 13.6 in my case), how does Elmer know whether the flow is from the outside towards the inside of th...
- 27 Apr 2011, 17:36
- Forum: ElmerSolver
- Topic: Cooling problem
- Replies: 27
- Views: 14981
Cooling problem
Hi, I've inherited a system that uses Elmer to simulate cooling electronic components. Basically, we model the components in 3D, then immerse them in a box of air and specify an air flow. I'm not an expert on FEM and/or thermal analysis and now I have to modify the system a bit for a new problem. He...
- 22 Mar 2011, 18:31
- Forum: ElmerSolver
- Topic: Mesh size and accuracy of results
- Replies: 1
- Views: 2523
Mesh size and accuracy of results
Hope I've posted in the correct forum -- if not, please move to appropriate place. I'm working on a simple problem which consists of a board, and component consuming power, all placed within an airbox. Elmer solves flow and heat equations. The ambient temperature (i.e. the temperature at the boundar...
- 01 Dec 2010, 19:26
- Forum: ElmerSolver
- Topic: Divergence (with NaN steps) for Navier-Stokes equation
- Replies: 16
- Views: 12984
Re: Divergence (with NaN steps) for Navier-Stokes equation
Here's a solution to defining physical volumes for Gmsh meshing when importing a .brep (or .step or .igs) file for meshing. It's not an Elmer thing per se, but it may be useful for other people since Gmsh+Elmer seems to be pretty popular. I'm attaching "demo.geo", and then comment it a bit...
- 01 Dec 2010, 16:58
- Forum: ElmerSolver
- Topic: Divergence (with NaN steps) for Navier-Stokes equation
- Replies: 16
- Views: 12984
Re: Divergence (with NaN steps) for Navier-Stokes equation
Hi, Thank you very much for all these suggestions. First, let me say that using -autoclean in elmergrid did the trick -- elmersolver now finishes and produces the same results as some other older test cases. However, what Peter said about physical entities makes me nervous. On a couple of small test...