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 Ben June 13, 2004 13:23

cylindrical pipes

Hi all. I have two questions

1) I need to model flow through two pipes (actually, oil passageways in an engine). These two pipes come together at a very sharp angle. It is not a bend in one continuous pipe, it is basically two intersecting pipes. How do I build this mesh? I tried two pipes drawn in different coordinate systems such that the pipes overlap, but then I don't know how to subtract or delete the overlapping cells. What is the best way to do this?

2) Can you have a flow that is driven purely by pressure? My objective in modeling this system is to find the necessary inlet pressure to avoid aeration-cavitation in the pipe. It would be nice if I could just specify the inlet pressure, but I think the program will need more info than that. Does anyone know a method similar to this I could use?

Thanks

 Jörn Beilke June 14, 2004 11:07

Re: cylindrical pipes

1) why don't you use stardesign for that? There are also a lot of other ways to do it, but they require at least some learning.

2) there is no problem with pressure at the inlet and outlet

 Ben June 14, 2004 11:48

Re: cylindrical pipes

I'm new at CFD and star-CD. I'm working at a university on a project. The only thing I know to use to build meshes is pro*am because that is what they have. If they have something else, like stardesign, for building meshes then I haven't found it. Do you know how to build the type of mesh I mentioned before using pro*am? I apologize for not mentioning this before.

 4xF June 14, 2004 14:09

Re: cylindrical pipes

You need a surface mesh or a CAD surface description to start with. Since proam is not so easy to learn, I would strongly recommend you to assist to a training course or get your advisor to show you how to use it. By the way, instead of doing complicated stuff in 3D, why don't you simply start with 2D planar investigations. Cavitation is difficult enough, so doing 2D simulations will give a feeling on how to use the code for this kind of physcis.

 Birute June 16, 2004 11:25

Re: cylindrical pipes

You can create this mesh even with STAR-CD mesh generator. Use the blocking approach. First option: Some steps: 1.Create mesh in two different coordinate systems (as you have done before, they can overlap) 2. Create splines at the ends of pipes and intersection parts(this is the most difficult part and needs some creativity). 3. Delete mesh 4. From splines create blocks. 5. From blocks create new mesh. This option can be time consuming, can take several days for begginer, no guaranty for good mesh.

Second option: Use pro*am, as you got advise before. I don't know much how to do that (personally I didn't like pro*am)

Third option: Use ICEM-CFD (if it is available), it will take several hours for begginer, even using tutorials and manuals.

Good luck!

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