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Ciro Cannavacciuolo August 5, 2008 07:05

planning hulls
 
Hi! I'm a cfx user and i'm trying to simulate the flow field around a planning hull. There is a big problem: i note the formation of a air film between the hull and the freesurface. Is there someone that studied this kind of simulation?

Thanks

troy August 7, 2008 22:44

Re: planning hulls
 
we do a lot of planing hull studies and we've seen the same problem. the amount of this "air film" depends entirly on the inflated boundary mesh settings (y+ value), velocity, and immersion. the software developers are well aware of the problem and we're told that they are currently trying to resolve it.

Ciro Cannavacciuolo August 8, 2008 05:24

Re: planning hulls
 
ok, thank you!

I noticed that, even if the "air film" is present, the lift calculated is not so different from the experimental data ( about 10% of error ).

Do you have some data about this?

Thanks

Charles August 13, 2008 05:02

Re: planning hulls
 
You get this in other VOF codes too. Try to reduce timestep.

cannavacciuolociro ciro August 15, 2008 05:04

Re: planning hulls
 
ok, thank you!

I did simulation with k epsilon turbulent model but i think that k omega is the best.

Don't you think so?

Thanks

Charles August 15, 2008 05:35

Re: planning hulls
 
mmmm. Don't expect it to make too much of a difference for this kind of flow. Anyway, what happens to the turbulence at the air / water interface is another interesting question by itself.


cannavacciuolociro ciro August 15, 2008 12:14

Re: planning hulls
 
the k omega model calculate RANS until the wall, without any wall functions. Maybe the problem of the "air film" between the hull and the surface is due to the effect of this wall functions. About the turbolence at the air/water interface i have never studied it. Cuold you tell me something about that? Thank you

Deepak Bansal August 9, 2013 16:12

air phase being formed on the bottom of the hull
 
hey buddy i am also facing same problem in planing craft that air phase being formed on the bottom of the hull.................how did u solve this problem.................reply as soon as possible...............


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