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 Js May 15, 2007 10:11

Rotating mesh motion

Hello everyone!

I would like to simulate a free motion of a bridge deck in Ansys-CFX 10. My question concerns how to rotate my bridge profile. Since mesh motion only allows specification of the cartesian coordinates x,t and z my idea is to define the displacement of each coordinate using trig. But have not made this work yet - and seems a little difficult. May be my trigonometric functions are wrong.

Is this the right approach, or is there an easier way to do this?

Else how to define my trig functions?

Thanks!

Jesper

 Glenn Horrocks May 15, 2007 18:31

Re: Rotating mesh motion

Hi,

Is this FSI or are you proscribing the motion of the bridge?

Glenn Horrocks

 Js May 16, 2007 02:20

Re: Rotating mesh motion

Hi Glen

This is not FSI. I would like to proscribe the motion of rotation of the bridge, and it needs to be by using mesh deformation, so a free motion can be submittet to the bridge profile lateron using the equation of motion.

I know how to rotate using subdomains, but the effect obtained by this is not what is sought here.

Regards Jesper

 Glenn Horrocks May 16, 2007 18:13

Re: Rotating mesh motion

Hi,

If you describe your mesh motion by CEL functions on the boundaries you are going to be limited in the range of rotations you can do before the mesh folds. You should be able to translate it a fair way but excessive rotations wil lead to mesh folding. It should work OK for small rotations, my guess is +/-30 degrees should be OK.

If you need larger rotations than that you will need to consider doing the rotations with a ggi and the translations superimposed on top of that.

Glenn Horrocks

 Js May 17, 2007 02:18

Re: Rotating mesh motion

Hi

I am defining the rotation by cel using trig functions. The rotation looks fine, but after the initial rotation the body starts to subtract (becomes smaller) and then stabalises in this shape. Why is that?

Jesper

 Glenn Horrocks May 17, 2007 19:00

Re: Rotating mesh motion

Hi,

If it just rotates then consider defining it as a rotating domain. Much easier and more accurate.

Glenn Horrocks

 Js May 18, 2007 02:22

Re: Rotating mesh motion

hi

In the ende it should define a free motion: rotation+ vertical movement.

A rotating domain will not work in this case.

But thanks

Jesper

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