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-   -   A lot of questions by a beginner (http://www.cfd-online.com/Forums/openfoam-meshing/110729-lot-questions-beginner.html)

Bullseye December 19, 2012 06:56

A lot of questions by a beginner
 
2 Attachment(s)
Hi,

i have a little problem. My adviser needs a simulation of the assembly(coldwallreactor) seeing in addendum.
I have done the tuts on the openFoam page.
Now my few questions

1.What foamer do i need for that? IcoFoam?
2. Is that possible to creat the mesh with blockMesh or should i take an other messure for that problem?
3. How shall i build up the mesh seeing sec. addemdum?
a.Create a big block, than omit all „air“ areas(
or
b.Create the „solid“ blocks first and than omit the „air“

wyldckat December 24, 2012 14:02

Greetings Bullseye and welcome to the forum!

You can do the mesh with blockMesh. I suggest SwiftBlock for doing this, since it should make your life a lot easier.

As for the solver, I can't figure out what's in play. You can try simpleFoam to get started, assuming it's a stationary fluid flow simulation.

Once you've got the mesh and something that works with simpleFoam, you can then ask for more information in the respective sub-forum (don't forget to detail a bit better what's in play): Running, Solving & CFD

Best regards,
Bruno

Bullseye January 10, 2013 09:36

Thank you I wanna try your tips :) But what do u mean with play? Should i describe how it works? Can Blender import .step so i can create the model in SolidEdge or must i learn how to create the model in blender? EDIT No Blender cant.

What swiftBlock file should i take from here?
https://github.com/nogenmyr/swiftBlock

wyldckat January 10, 2013 17:25

Hi Bullseye,
  1. Export to STL instead of STEP.
  2. Use the big ZIP button or this link: https://github.com/nogenmyr/swiftBlo...ive/master.zip
  3. Instructions on how to install plugins in Blender: http://wiki.blender.org/index.php/Do...Python/Add-Ons
Best regards,
Bruno

wyldckat January 10, 2013 18:45

Quote:

Originally Posted by Bullseye (Post 401190)
But what do u mean with play? Should i describe how it works?

I forgot to answer these questions - I mean "what's in play" in the sense of "what happens where, how and why"!?

In other words:
  • Is is compressible or incompressible?
  • Is there more than one fluid or is it a gas mixture?
  • What fluid speeds (and/or Reynold number) are involved?
  • Is it stationary or transient? For example, if you expect that moving vortexes will appear during the simulation, then it should probably be transient.
  • etc...
Because without this kind of information, the best suggestion would probably be: use "potentialFoam", which is a veeery basic solver that only solves a potential function of velocity vs pressure, if I'm not mistaken. Not exatly physical, but it provides a solution... for the potential function of velocity vs pressure :D

Best regards,
Bruno

Bullseye January 12, 2013 10:56

Is is compressible or incompressible? :) its incompressibe:) Is there more than one fluid or is it a gas mixture? :)It is a gas mixture. Most is N2 97% followed by H2 and C2H2 :) What fluid speeds (and/or Reynold number) are involved? :) laminar flow, velocity max 0.35 m/s :) Sorry for no formating the text, but java a a big gap, so i have dissabled it for browsing

wyldckat January 13, 2013 08:13

As far as I know, you can use simpleFoam, as long as there is no chemical reaction, the gas is perfectly mixed in all zones and that you have enough information about the fluid properties of this gas mixture.

Best regards,
Bruno

Bullseye January 15, 2013 10:15

1 Attachment(s)
Thank you Bruno,

i installed Blender and swiftBlock and im doing my first little steps with both of them.

My next questions are:

2D or 3D Modell?
My advisor ment, that the real mesurements are just 2D.

Real pipe, like addendum or just a massive, round rod?
How to create the gap between pipe and heating element is that necessary?
Should i create 3 single elements or is it possible to build one part like addendum?

ok simpleFoam if no chemical reaction and if there is a chemical reaction not know but in future?

But why no icoFoam?

Cause in the UserGuide i read for simpleFoam "Steady-state solver for incompressible, turbulent flow". But i have no turbulents i it neither after "impact" at Si-Wafer

wyldckat January 19, 2013 16:42

Hi Bullseye,

Quote:

Originally Posted by Bullseye (Post 401959)
2D or 3D Modell?
My advisor ment, that the real mesurements are just 2D.

If it's 2D, it would be quickest to set-up if you could use only blockMesh (with the help of SwiftBlock), simply because with snappyHexMesh things get a bit tricky for generating a 2D mesh.

Quote:

Originally Posted by Bullseye (Post 401959)
Real pipe, like addendum or just a massive, round rod?
How to create the gap between pipe and heating element is that necessary?
Should i create 3 single elements or is it possible to build one part like addendum?

You're new to OpenFOAM, so keep it as simple as possible! You should start with the most simplest form of geometry and then evolve gradually from there.
This is OpenFOAM, it is not Fluent, Star-CCM+ nor any other commercial CFD application. If you don't start small and gradually grow your case, you'll be stuck in the same place for a looooooong time...

Quote:

Originally Posted by Bullseye (Post 401959)
ok simpleFoam if no chemical reaction and if there is a chemical reaction not know but in future?

When chemical reactions come into play... you better be very certain of what types of reactions you need! OpenFOAM has got several solvers that involve chemistry, which you can check by looking into the "tutorials" folder, namely:
  • combustion/
  • discreteMethods/
  • lagrangian/
Worst case-scenario: you might even have to create your own solver, in case neither one of these solvers satisfy your needs.

Quote:

Originally Posted by Bullseye (Post 401959)
But why no icoFoam?

Have you read the OpenFOAM User Guide? Have you done the tutorials on the User Guide? I'm asking this because icoFoam requires that you manually take into account the Courant number, while simpleFoam doesn't need it.

Nonetheless, if you want to use icoFoam, I suggest you study very well the User Guide, as well as searching online for more information about icoFoam!

Quote:

Originally Posted by Bullseye (Post 401959)
Cause in the UserGuide i read for simpleFoam "Steady-state solver for incompressible, turbulent flow". But i have no turbulents i it neither after "impact" at Si-Wafer

simpleFoam can easily handle laminar flow, since you can turn off turbulence. Check the files inside the "constant" folder.

Best regards,
Bruno

Bullseye January 24, 2013 11:07

Thank u a lot of stuff, i can work with it :)


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