topic Re: Pressure Simulation - How to do an underwater simulation? in Fusion Design, Validate & Document Forum

Pressure Simulation - How to do an underwater simulation?

Anonymous — Wed, 24 Feb 2016 17:32:23 GMT

Hello! I'm designing a hollow waterproof camera case for scuba diving and when I run a pressure simulation I always have to pick a constraint. The issue is any constraint I select causes the pressure simulation to warp towards it (see below).

I'm hoping to run a simulation like it is underwater with all the pressure pushing inward (not inward and toward the constraint). Picture a case suspended neutrally buoyant in the water 130 ft deep with pressure surrounding it.

The closest I've gotten is suspending a sphere in the middle of the case and constraining it but even that gives false results. (see below)

Any ideas? Thanks!!!

-Michael

Re: Pressure Simulation - How to do an underwater simulation?

innovatenate — Wed, 24 Feb 2016 23:36:58 GMT

You must have a constraint on the model that will fix it in space. If you use the DOF View from the display drop down menu, it can help show which bodies/components are fixed versus which ones have DOF's where the body/component will move under a load.

I hope this helps.

Thanks,

Re: Pressure Simulation - How to do an underwater simulation?

Anonymous — Thu, 25 Feb 2016 15:38:21 GMT

Thanks for the fast reply! That's what I was afaird of, and I've been using the DOF View.

The problem is any place I put a constraint, the stress and displacement are locked there and everything warps towards it. Or is there a way to constrain it without that happening?

For example how would you run a displacement simulation of a ballon in a pressurized room or in my case, an empty camera housing suspended underwater?

Thanks!

Re: Pressure Simulation - How to do an underwater simulation?

kb9ydn — Thu, 25 Feb 2016 18:01:19 GMT

@Anonymous wrote:
Thanks for the fast reply! That's what I was afaird of, and I've been using the DOF View.

The problem is any place I put a constraint, the stress and displacement are locked there and everything warps towards it. Or is there a way to constrain it without that happening?

For example how would you run a displacement simulation of a ballon in a pressurized room or in my case, an empty camera housing suspended underwater?

Thanks!

In the study settings, try enabling "remove rigid body moves". This way you can run the solver with no structural constraints at all. It will give a warning but you can ignore it.

Re: Pressure Simulation - How to do an underwater simulation?

innovatenate — Thu, 25 Feb 2016 19:20:46 GMT

The model needs constraints to eliminate rigid body motion (a.k.a. the model "flying off in space").

You could add a few split's to a face and then constrain those edges to be fixed in one direction. If you pick and choose what directions you are constraining on and which faces, you may be able to get close to your goal. Check out the below sample file for more detail.

http://a360.co/1SXXbNb

Hope that helps!

Re: Pressure Simulation - How to do an underwater simulation?

kb9ydn — Thu, 25 Feb 2016 19:30:39 GMT

@innovatenate wrote:
The model needs constraints to eliminate rigid body motion (a.k.a. the model "flying off in space").

You could add a few split's to a face and then constrain those edges to be fixed in one direction. If you pick and choose what directions you are constraining on and which faces, you may be able to get close to your goal. Check out the below sample file for more detail.

http://a360.co/1SXXbNb

Hope that helps!

But if you change the setting I showed above it doesn't fly off into space when you remove all the constraints. Try it and you'll see what I mean.

Re: Pressure Simulation - How to do an underwater simulation?

innovatenate — Thu, 25 Feb 2016 20:23:17 GMT

Awesome tip! I over-looked that setting. Thanks!

I note that you can edit the remove rigid body modes setting by selecting Manage > Setting for an exisiting simulation.

Or in the New Study dialog (expand the options!)

You'll still get the warning to add a constraint, but if you select continue, it will ignore the warning and solve anyway.

Thanks for the help!

Re: Pressure Simulation - How to do an underwater simulation?

Anonymous — Thu, 25 Feb 2016 20:52:17 GMT

AWESOME!!! Thank you kb9ydn and Nathan!!! That works prefectly!

-Michael