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## Simulation CFD

Contributor
Posts: 15
Registered: ‎11-26-2012

# How to set up the motion when one object is constrained by another

99 Views, 7 Replies
11-29-2012 01:55 PM

Hi guys,

I am having problems with the set up of the motion on two different parts in Autodesk CFD, where both parts are in motion and they move with respective each other.

Thanks

Shoeb.

Product Support
Posts: 584
Registered: ‎08-25-2011

# Re: How to set up the motion when one object is constrained by another

11-30-2012 03:20 AM in reply to: sshoeb42

Hi,

Do both parts move together? If so you need to place them in a group (but switch it to motion rather than geometric).

If they move based on the position of each other but not together, the only way to do this would be to prescribe their position relative to time.

Does that help?

Jon Wilde
Contributor
Posts: 15
Registered: ‎11-26-2012

# Re: How to set up the motion when one object is constrained by another

11-30-2012 06:33 AM in reply to: wildej
Hi, my case is the second one where both parts have to move based on the position of each other....but the problem is one is flow driven and other is reciprocating.... how can i go about it.... Thanks Shoeb.
Product Support
Posts: 584
Registered: ‎08-25-2011

# Re: How to set up the motion when one object is constrained by another

11-30-2012 06:45 AM in reply to: sshoeb42

Hi Shoeb,

If they are not related, as you say one is flow driven and the other is reciprocating, can you not just assign each the respective settings?

Perhaps I am not understand the question fully.

Jon Wilde
Contributor
Posts: 15
Registered: ‎11-26-2012

# Re: How to set up the motion when one object is constrained by another

11-30-2012 06:55 AM in reply to: wildej
Hi, They are two parts, lets call poppet valve which resides in the reciprocating part. I am not finding a way to bound the motion of the valve with the reciprocating part, where the valve is flow driven and the other part is reciprocating. Thanks Shoeb.
Product Support
Posts: 584
Registered: ‎08-25-2011

# Re: How to set up the motion when one object is constrained by another

11-30-2012 07:03 AM in reply to: sshoeb42

Thanks,

Jon

Jon Wilde
Contributor
Posts: 15
Registered: ‎11-26-2012

# Re: How to set up the motion when one object is constrained by another

11-30-2012 07:05 AM in reply to: wildej
Nope, I just posted here. Thanks Shoeb.
Product Support
Posts: 584
Registered: ‎08-25-2011

# Re: How to set up the motion when one object is constrained by another

11-30-2012 07:31 AM in reply to: sshoeb42

OK, thanks for letting me know.

There is a possibility we could do this but it would be very difficult and we are not sure if it would be a success.

You could try assigning the reciprocation to one part and allowing the other to be flow driven, and constrained by the solid parts.

What you would need to do first is move both moving parts out of the model in CAD, to ensure we have a good mesh (with boundary layers) before the parts are moved back into the model in CFD, using the 'initial position' option within the motion setup. This seems a little strange until you think about it. With the solids in place, the boundary layer would be created in the fluid, and would not move with the solids - this is not ideal, moving the parts out of the fluid avoids this.

Please be sure to turn the mesh enhancement ON before you run, it will automatically be switched off by CFD as soon as you assign motion. Also, use ADV5.

You will also need a uniform mesh on the 2 parts and the fluid they move within - it might be worth adding a mesh region within CAD to help you to do this.

I am happy to take a look if you have a cfz pre-setup with the parts outside of the model and the meshing region, materials and boundary conditions all ready to go so I know what you are aiming for.

Bear in mind that we are not sure if this will work OK or not, but it might be worth a try.

Jon Wilde