[ben1793]

I really want to learn openfoam, not for studying or work but just because I find it interesting, I have been reading up on fluid dynamics and programming and want to finally try out some tutorials, after struggling a lot I finally got Ubuntu and now am trying to install openfoam, I am still getting used to Linux and also using the terminal so am having problems installing openfoam.
I have gotten to the following point so far:
http://www.openfoam.org/download/ubuntu.php
up to the user configuration, I have managed to do the first part of this (opening the text file with the terminal) but I can not save it, it says save it in OpenFOAM/etc, which I have found but there is already a text file with the same name in there and also when I try overwrite it it says you do not have permission make sure it is being saved in the right place.

Please help me. Thank you.

[wyldckat]

Greetings Ben,

There's a quicker and easier way to install OpenFOAM... or at least it should be
Simply follow the instructions given here: https://github.com/themiwi/OpenFOAM-Installer

Best regards,
Bruno

[ben1793]

Wow, thank you, this was so much easier

[ben1793]

Rather than making a new thread I thought I would just ask my questions on here, I am looking at the Cavity tutorial, I realized that after the hex has been made it has a simplegradiant with a ratio (2 1 1) which I now know that it means the ratio of cells in the x direction(last cell will be 2x the size of the first in the x direction), what I do not understand is what difference this would make? What difference does the size of the cells make to anything?

Thank you in advance.

[wyldckat]

Hi Ben,

Well... for the next question or array of questions, it might be best to create a new thread .

OK, it's simple: mesh cells is a discretization of a volume. The more cells and the smaller they are, the better the resolution. Pretty much the same as when taking digital photographs.
Problem is that the more cells you have, the heavier it gets: more RAM and more CPU power is needed.

So, you have to balance both sides: when you're solving a problem, you need just enough resolution for properly simulating each zone of the volume. But you can't over do it on the resolution, because you've always got a time and resources constraint, as well as the solver itself might not be able to solve minute details, such as interactions at a molecular level... if the cells are cubes of 1e-20 m wide

But since you're new to CFD, here's a nice list of lessons which should help you clear up a lot of questions: http://www.youtube.com/playlist?list=PL30F4C5ABCE62CB61 - I've never saw them myself, so I don't know the level of complexity in them

Also check my signature link, you should find various good links for newbies near the end of the blog post.

Best regards,
Bruno

[ben1793]

Thank you for clearing things up and for the links

I will make a new thread once I have a few more questions to ask

[ben1793]

hello again

What is the difference between using something like Autodesk simulator CFD and OpenFOAM? I saw tutorials for Autodesk Simulator CFD and it seems quite straight forward, no coding, no formulas, just specify things like pressure, boundry conditions, inlets, outlets, etc and simulate it to get the results, is this software not as accurate as OpenFOAM? There is something I found on it called mesh generation and it basically generates the mess automatically without you needing to specify anything apart from the faces you want it generating on, is there anything like this on OpenFOAM?

[wyldckat]

Originally Posted by ben1793

What is the difference between using something like Autodesk simulator CFD and OpenFOAM? I saw tutorials for Autodesk Simulator CFD and it seems quite straight forward, no coding, no formulas, just specify things like pressure, boundry conditions, inlets, outlets, etc and simulate it to get the results, is this software not as accurate as OpenFOAM? There is something I found on it called mesh generation and it basically generates the mess automatically without you needing to specify anything apart from the faces you want it generating on, is there anything like this on OpenFOAM?

This is definitely a question for a new thread. Anyway, the quick answer is this:

• OpenFOAM is open source and completely free.
• Autodesk Simulator CFD is not.
• You can go look in the CFD-Online Forums directory and you'll see a small glimpse that there are several CFD applications/toolboxes in existence: http://www.cfd-online.com/Forums/

Which one is better? It's almost the same as comparing Windows OS with any/all Linux distributions and Mac OS X: freedom and usability are always at stake.


The big difference when it comes to CFD is this: validation of results may vary, depending on the type of simulation you're doing! Some have been designed and tested for some things and others have been designed for the other things.


Search for OpenFOAM vs Fluent and so on and you'll find out that this has been asked several times in the past.

[akidess]

In addition to what Bruno said - if you exclude coding, you will be quite limited in what you can do with any software package. Ansys Fluent is extensible by using "User defined functions" (and I'm sure other solvers are too). So if you're looking at a complex problem you are likely to do some coding anyway, and that might come more natural in OpenFOAM as you can see the entire code, and use standard debugging tools.

- Anton

Originally Posted by ben1793

hello again

What is the difference between using something like Autodesk simulator CFD and OpenFOAM? I saw tutorials for Autodesk Simulator CFD and it seems quite straight forward, no coding, no formulas, just specify things like pressure, boundry conditions, inlets, outlets, etc and simulate it to get the results, is this software not as accurate as OpenFOAM? There is something I found on it called mesh generation and it basically generates the mess automatically without you needing to specify anything apart from the faces you want it generating on, is there anything like this on OpenFOAM?

[ben1793]

Thank you for the replies, I will defiantly make a new thread for my next questions.