how to set Reciprocating and Rotation motion in CFX

aja1345 · May 21, 2016, 05:54

Hi,

I want to model the following case:

This case have reciprocating and rotation motion. Is it possible that this case models in CFX without writing Code?

I am grateful that guide me.

Thanks.

Best.

Aja

ghorrocks · May 21, 2016, 07:00

This is quite straight forward. The reciprocating motion is a simple moving mesh application - but you need to be careful about how you apply it to make it work nicely. The rotation is simply a tangential velocity on the wall boundary, assuming the rotation does end up with just a tangential velocity on the wall.

How big is the reciprocation? How big is the domain width?

aja1345 · May 21, 2016, 07:40

Quote:

Originally Posted by ghorrocks

This is quite straight forward. The reciprocating motion is a simple moving mesh application - but you need to be careful about how you apply it to make it work nicely. The rotation is simply a tangential velocity on the wall boundary, assuming the rotation does end up with just a tangential velocity on the wall.

How big is the reciprocation? How big is the domain width?

reciprocation is between top wall and bottom wall....I want to just simulate this 2 Dimensional model currently. Then, I have to simulate its 3
Dimensional model...therefore, first I want to learn how to set this case and I don't know exact dimensions. According to your statement, i have to study moving mesh because i didn't work moving mesh in Fluent and CFX. Can you explain more about your following statement?why are you saying it?

"but you need to be careful about how you apply it to make it work nicely"

If it is possible, please give me useful links and documentations.

Thanks.

ghorrocks · May 21, 2016, 07:56

You have to be careful how you apply it as it is easy to squash the mesh too far and you get negative volume elements and poor quality mesh. You sometimes need to be a little cunning to create a motion which maintains good mesh quality.

If the motion is from the top wall to the bottom wall then this will be tricky with moving mesh alone. You are probably going to need remeshing as well.

Examples of all this is available on the ANSYS customer webpage.

aja1345 · May 21, 2016, 07:57

Quote:

How big is the reciprocation?

aja1345 · May 23, 2016, 01:50

Hi,

In this simulation, Should i add a new material(solid) except Fluid(water)?

Thanks.

ghorrocks · May 23, 2016, 08:08

You do not model the reciprocating/rotating object as a solid. You model it as a section cut out of the fluid domain.

May 21, 2016, 05:54	how to set Reciprocating and Rotation motion in CFX	#1
aja1345 Senior Member Aja Join Date: Nov 2013 Posts: 496 Rep Power: 15	Hi, I want to model the following case: This case have reciprocating and rotation motion. Is it possible that this case models in CFX without writing Code? I am grateful that guide me. Thanks. Best. Aja Last edited by aja1345; June 12, 2016 at 11:06.

May 21, 2016, 07:00		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	This is quite straight forward. The reciprocating motion is a simple moving mesh application - but you need to be careful about how you apply it to make it work nicely. The rotation is simply a tangential velocity on the wall boundary, assuming the rotation does end up with just a tangential velocity on the wall. How big is the reciprocation? How big is the domain width? aja1345 likes this.

May 21, 2016, 07:56		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	You have to be careful how you apply it as it is easy to squash the mesh too far and you get negative volume elements and poor quality mesh. You sometimes need to be a little cunning to create a motion which maintains good mesh quality. If the motion is from the top wall to the bottom wall then this will be tricky with moving mesh alone. You are probably going to need remeshing as well. Examples of all this is available on the ANSYS customer webpage. aja1345 likes this.

May 23, 2016, 08:08		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	You do not model the reciprocating/rotating object as a solid. You model it as a section cut out of the fluid domain. aja1345 likes this.

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