Advice using dsmcFoam
 

Good evening!

My name is Jacob and I'm currently a sophomore in college. I'm in an undergraduate research program and my mentor gave me a project to work on that I will talk about at an AIAA symposium this December. The research he's given me, however, is quite honestly above my head, because I've never taken a fluids class (but this is how research works: you tackle a problem that's difficult to solve by gathering information).

As a lot of us know, the learning curve for OpenFOAM is quite steep; the fact I've never worked with C++ programming also tremendously hurts. So I am having a lot of issues on figuring out how to work with OpenFOAM in general. I understand the basic concepts with the files, and how there's three directories (0, constant, and system), and that 0 describes the conditions at t=0... But after that, I'm pretty lost.

My project is simple: simulate a sphere of radius 0.01m at mach 10 speed in an argon gas flow... Well, although it is simple, it is very difficult for me! This is basically what my mentor set me up with. Everything else is up to me to figure out on my own. Afterwards, he eventually told me to use the conditions found in Thomas Hauser and Jeffery Allen's paper on dsmcFoam... Hauser's paper mentioned "a mean free path of 0.0068m... a domain of 9200 unstructured tetrahydral cells... time step of 6.5E-7... sphere wall temperatures were set to 1000K..."

So... My question is: how does OpenFOAM work? Does anybody know how to use dsmcFoam solver? Most importantly, is there any advice you can give me as to where I can find information on these topics? I've searched endlessly (hence why I'm finally posting about it). But perhaps I've searched in all the wrong places...

Thank you, and I apologize for this wall of text!
-Jacob Hempel

No advice? Am I being too vague?

Hello Jacob,

I was in the exact same spot a couple of months ago so I have some idea what you are going through. I have never worked with dsmcFoam before nor am I an expert on OpenFOAM, but perhaps I can give you some general advice which might be helpful to you:

1. Have you already done all the three tutorials mentioned in the User Guide? I found that doing those and reading chapters 3-5 gave me a good insight on how to set up the case files.

2. A little understanding of C++ would really come in handy when you are working with OpenFOAM. I found this guide really helpful to brush up my knowledge of C++ http://www.cplusplus.com/files/tutorial.pdf

3. Have you made any progress with your case so far? One thing that I have learned is that if you are expecting any help from this forum, you got to be very specific. I guess the first step for you should be to decide upon the shape, dimensions, no. of cells, etc. for your mesh.

Hope this helps. Good luck!

Sagun

Thank you for your reply! It tremendously helps.
To answer your question: I've only built a mesh using Pointwise. I then exported the files in OpenFOAM format, so I don't really think it's necessary to produce any mesh code (correct me if I'm wrong on that). So, as of now, I have a mesh and that's all.

I've completed the first tutorial in the userguide, but that's all. I will start on the second and third, and I will begin reading chapters 3-5. I'm glad I'm not the only one who (at least begins) in confusion with OpenFOAM.

Thank you! :)
-Jacob

I also discovered some dsmcFoam tutorials under the category discreteMethods of OpenFOAM tutorials. You should definitely check out those to get an idea about how to set up your case files.