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michaelperry2011
Posts: 5
Registered: ‎05-30-2013

CFD for boat hulls

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05-30-2013 06:24 PM

I have designed a boat hull and can export it to .stl, .igs, and eventually Inventor formats. Is there a way to model a hull moving through water using this software.

I seem to be hitting quite a learning curve, and the documentation that Autodesk is providing is marginal, at best.

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apolo.vanderberg
Posts: 299
Registered: ‎08-31-2011

Re: CFD for boat hulls

06-03-2013 05:50 AM in reply to: michaelperry2011

Yes,

this would be similar to any other external aero application only you would have to combine it with our Free Surface capability (in 2014).

 

Boat would be caded in the middle of a large domain - all assigned as water

Lower half of the domain would be assigned Height of Fluid Initial Condition as well as Compnent Velocity (Vx / Vy /Vz)

Boundary condition to dictate the velocity the water comes in at and a zero pressure for the outlet

 

Fine mesh at the water level to capture surface effects as well as an appropriately small timestep size -  I've posted on some of the other free surface threads about some of this.

 

 

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OmkarJ
Posts: 434
Registered: ‎10-02-2012

Re: CFD for boat hulls

06-03-2013 07:16 AM in reply to: apolo.vanderberg

Apolo,

 

If I may ask, is there any special treatment given to the advection terms for volume fractions, in terms of discretization scheme? This would be necessary for keeping the interface sharp, instead of smeared.

 

OJ

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michaelperry2011
Posts: 5
Registered: ‎05-30-2013

Re: CFD for boat hulls

06-06-2013 06:23 PM in reply to: michaelperry2011

Thanks for the reply. I am just now getting into CFD so pardon my ignorance. What do you mean by caded?

For now I am just getting used to the free surface application and moving fluid between volumes, and around steps. Much like in a flume.

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wildej
Posts: 778
Registered: ‎08-25-2011

Re: CFD for boat hulls

06-07-2013 01:09 AM in reply to: michaelperry2011

It might be better written as CAD'd, so within your CAD system, placed into a large domain.

 

A flume would be different though as you need no initial water level - just a really good mesh.



Jon Wilde
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apolo.vanderberg
Posts: 299
Registered: ‎08-31-2011

Re: CFD for boat hulls

06-07-2013 05:53 AM in reply to: wildej

Yes, sorry as Jon mentioned CADed / CAD'd - done in cad.

 

Omkar, we do have a smoothing algorithm applied to the VOF=0.5 to help with rendering of the results.

I dont specifically have the details as to what terms it is applied to at the moment.

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OmkarJ
Posts: 434
Registered: ‎10-02-2012

Re: CFD for boat hulls

06-10-2013 01:39 AM in reply to: apolo.vanderberg

Thanks, I assume that mostly, this would be a transient simulation -meaning, mesh adaptation is not possible (I guess?). How do you suggest one should determine the mesh size to capture the interface adequately? And what about timesteps - perhaps Intelligent Solution Control is necessary here always?

 

OJ

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wildej
Posts: 778
Registered: ‎08-25-2011

Re: CFD for boat hulls

06-10-2013 01:57 AM in reply to: OmkarJ

Hi Omkar,

 

Yes, all Free Surface analyses must be transient. We suggest a uniform mesh on the water surface and then I tend to apply a region around the boat and wake, in a section of the air and water with a finer mesh.

CFD will control the timestep after it is running, I would still start small though, maybe 0.01 of a second, which is what I used on my last hull model.



Jon Wilde
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