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-   -   Aerodynamic simulation (http://www.cfd-online.com/Forums/star-ccm/87752-aerodynamic-simulation.html)

Maicol April 28, 2011 08:28

Aerodynamic simulation
 
Hi everybody,
I have to make an aerodynamic simulation, how can I build a control volume (such as a wind tunnel)after importing the geometry I have to simulate?
then, once I have made this system (body + wind tunnel) which is the best way to operate: give solid properties to body and fluid to control volume, or make a boolean operation to subtract body from control volume and give fluid properties to the resulting volume?
thank you!

rwryne April 28, 2011 08:39

Quote:

Originally Posted by Maicol (Post 305413)
Hi everybody,
I have to make an aerodynamic simulation, how can I build a control volume (such as a wind tunnel)after importing the geometry I have to simulate?
then, once I have made this system (body + wind tunnel) which is the best way to operate: give solid properties to body and fluid to control volume, or make a boolean operation to subtract body from control volume and give fluid properties to the resulting volume?
thank you!


Import the geometry as a part, create a box part to the size you want, then do a boolean subtract with the box part as the "target part"

Maicol April 28, 2011 10:32

very kind of you, many thanks

Maicol April 29, 2011 05:30

I tried the way you suggested, I subtracted a sphere from a tunnel (in STAR DESIGN), it works correctly.
I tried onother way, too: import two separate bodies in STAR CCM, but i have a problem to asign properties to singular bodies (such as physical properties, mesh sizing etc..): when I am importing geometries, which is the best way to import: create a new region or a new part?
Have you ever made something similar?
I really thank everyone of you is interested in giving me an answer

rwryne April 29, 2011 09:52

Quote:

Originally Posted by Maicol (Post 305570)
I tried the way you suggested, I subtracted a sphere from a tunnel (in STAR DESIGN), it works correctly.
I tried onother way, too: import two separate bodies in STAR CCM, but i have a problem to asign properties to singular bodies (such as physical properties, mesh sizing etc..): when I am importing geometries, which is the best way to import: create a new region or a new part?
Have you ever made something similar?
I really thank everyone of you is interested in giving me an answer


I prefer to import as a part. You then need to create an empty region with boundaries and assign the surfaces of the part to the region boundaries. Then do Mesh->Initialize Meshing, which transfers the geometric data from the Part level to the Region level.
It is a good habit to import as a part as I have heard that eventually CD-Adapco is going to do away with the import as region.

Maicol April 30, 2011 11:03

Thank you Ryne!

abdul099 May 1, 2011 07:32

Quote:

Originally Posted by rwryne (Post 305609)
I prefer to import as a part. You then need to create an empty region with boundaries and assign the surfaces of the part to the region boundaries. Then do Mesh->Initialize Meshing, which transfers the geometric data from the Part level to the Region level.
It is a good habit to import as a part as I have heard that eventually CD-Adapco is going to do away with the import as region.

When you've imported a part, you can right-click on it and choose either "set region" (older versions) or "assign parts to regions" (newer versions). That helps much saving time as you don't have to create a region and boundaries by hand and assing surfaces to boundaries.

Maicol May 2, 2011 06:25

Thanks for your suggestion Abdul...I tried this way too :) I have to define 2 mesh and 2 physic cases to define properties for 2 parts, isn't it?

rwryne May 2, 2011 08:17

Quote:

Originally Posted by abdul099 (Post 305765)
When you've imported a part, you can right-click on it and choose either "set region" (older versions) or "assign parts to regions" (newer versions). That helps much saving time as you don't have to create a region and boundaries by hand and assing surfaces to boundaries.


Yes, thank you for correcting me, this is how I typically do it. Much easier than doing it by hand.

abdul099 May 3, 2011 03:34

Quote:

Originally Posted by Maicol (Post 305901)
Thanks for your suggestion Abdul...I tried this way too :) I have to define 2 mesh and 2 physic cases to define properties for 2 parts, isn't it?

No. As long as they share the same physics, you need only one physics continuum. But you shouldn't have two ISOLATED parts, there should be some connection like interfaces between them.
And for the mesh continuum, you usually use only one as well as long as you don't want to give completely different values or models to different regions.

Will you have two regions? When doing so, is it necessary to have two regions?

Maicol May 3, 2011 07:58

Quote:

Originally Posted by abdul099 (Post 306041)
No. As long as they share the same physics, you need only one physics continuum. But you shouldn't have two ISOLATED parts, there should be some connection like interfaces between them.
And for the mesh continuum, you usually use only one as well as long as you don't want to give completely different values or models to different regions.

Will you have two regions? When doing so, is it necessary to have two regions?

in case of a air flow on a solid body i should have a physics continuum for solid part and a physics continuum to define gas properties..am i saying a right thing?

rwryne May 3, 2011 08:30

Quote:

Originally Posted by Maicol (Post 306075)
in case of a air flow on a solid body i should have a physics continuum for solid part and a physics continuum to define gas properties..am i saying a right thing?

If you are only interseted in the air flow, then you do not need a continuum for the solid part. You will only need the 2nd continuum if you are intersted in something like the heat transfer through the solid.

Maicol May 3, 2011 09:48

Quote:

Originally Posted by rwryne (Post 306079)
If you are only interseted in the air flow, then you do not need a continuum for the solid part. You will only need the 2nd continuum if you are intersted in something like the heat transfer through the solid.

Ok..however I have to mesh both the "solid" region and the fluid region, isn't it?

rwryne May 3, 2011 10:51

Quote:

Originally Posted by Maicol (Post 306097)
Ok..however I have to mesh both the "solid" region and the fluid region, isn't it?

Think about it in terms of volume mesh, not surface mesh. You only need a volume mesh where your interests lie. If you are just interested in the aerodynamic solution, you only need a volume mesh in the flow field.

The volume mesh of the flow field will use the surface boundaries of the solid body.

Maicol May 5, 2011 02:21

thank you Ryne, I will check the simulation using one volume mesh


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