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Make an stl file a domain for CFD

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I need to do a CFD simulation with Comsol. I have an STL file with a mesh describing the surface of an object on which I would like to do some fluid dynamics simulation. As far as my understanding goes, this file is just a collection of triangles.

My strategy for the simulation goes as follows:

- I made a new 3D, Fluid Flow, Stationary State project
- I used geometry -> import feature to import my STL file (this works fine) (you can see a picture at i.stack.imgur.com/1Smsq.png). As you can see, my object gets automatically partitioned in surfaces. Is this correct?
- I then do Geometry -> Add block to describe the space within which I want my air to flow. In this example I placed it so that my object lays outside the block, but I tried also to put it inside and nothing of what follows changed
- I proceed to assign materials. I would like my object to be in nylon. So I go to materials, open the dropdown menu of built-ins, and then I try to select my object. This does not work. The only thing that I apparently get to select is the block (you can see a picture at i.stack.imgur.com/4GE5o.png). If I select "All domains" to add it manually, only one domain shows up and it is the block.

Am I doing something wrong? My intuition says that I should somehow tell comsol that that geometry that I imported represents a closed object, and that I need it to be considered as a domain, but I wouldn't know how to do such a thing.

Thank you

Matteo

1 Reply Last Post 13 nov. 2014, 11:12 UTC−5
Beatrice Carasi COMSOL Employee

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Posted: 10 years ago 13 nov. 2014, 11:12 UTC−5
Dear Matteo,

I guess your thoughts are correct and to assign a domain material your imported geometry should be transformed in a domain; there are many ways to do so, but the best I will only be able to suggest if I tried them. Would you like to attach the model? It is not clear to me exactly what is the purpose of your modeilng and why should that be a domain at all.

By

Bea
Dear Matteo, I guess your thoughts are correct and to assign a domain material your imported geometry should be transformed in a domain; there are many ways to do so, but the best I will only be able to suggest if I tried them. Would you like to attach the model? It is not clear to me exactly what is the purpose of your modeilng and why should that be a domain at all. By Bea

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