Waves with hull

Julian_Maldonado · November 12, 2009, 13:42

Dear Glen,

I use to visit this forum and always see that your response are very close.

Please could you give me a pice of advice?, I need to simulate waves with hull but I can't find the way to do it.
I started with sin cos in Vx and Vz inlet, but was wrong.
Is necessary to move the inlet like a plate to simulate the wave, or can I do it with some function on CCL and ad the ship velocity.
I have CFX 11

Best Regards,

Julian

ghorrocks · November 12, 2009, 17:59

The best way of doing it is to specify the wave profile using a CEL expression. Remember you will need to specify volume fraction and velocity to get a realistic wave profile. This page (http://www.flow3d.com/resources/news...mmer09_02.html - on the Flow3D website!) has a good introduction to it. Hopefully you can implement some of this stuff in CFX.

Julian_Maldonado · November 13, 2009, 12:42

Dear glen,
Thanks for the info.
The problem is how to implement the input waves in CFX 11.
When I set the wave as senH + CosH or sen function, the problem is in the outlet, there are some reflection even with opening. The problem start with Velocity inthe inlet.
No problem if there are only the wave function. But when I set the velocity the simulation crash.
Do you know how to implement a wave on CFX 11 in the inlet+Velocity, for a hull simulation?

best regards and Thanks

J.

ghorrocks · November 14, 2009, 06:53

Non-reflecting boundary conditions are a major problem for CFD in general, they are not easy to do. V12 does have a new non-reflecting boundary condition option (I think it is a beta option) so have a look at that. Alternately I have heard of people putting a very coarse grid at the exit connected with a GGI to the main grid. When waves hit the coarse mesh the high numerical dissipation of the coarse grid damps the waves (I have never tried this but it sounds interesting!)

Julian_Maldonado · November 14, 2009, 07:14

Dear Glen;
Thanks again.
I'll try to test it on V12.
Please if you have more info or any help please don't doubt to contact me.

Best regards,

Julian

cfxmar · May 19, 2010, 06:35

Hello!

You could try also to put a higher water viscosity at the end of the domain in order to stop waves to come back.

November 12, 2009, 13:42	Waves with hull	#1
Julian_Maldonado New Member Julian Join Date: Mar 2009 Location: Spain Posts: 6 Rep Power: 17	Dear Glen, I use to visit this forum and always see that your response are very close. Please could you give me a pice of advice?, I need to simulate waves with hull but I can't find the way to do it. I started with sin cos in Vx and Vz inlet, but was wrong. Is necessary to move the inlet like a plate to simulate the wave, or can I do it with some function on CCL and ad the ship velocity. I have CFX 11 Best Regards, Julian

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November 12, 2009, 17:59		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,848 Rep Power: 144	The best way of doing it is to specify the wave profile using a CEL expression. Remember you will need to specify volume fraction and velocity to get a realistic wave profile. This page (http://www.flow3d.com/resources/news...mmer09_02.html - on the Flow3D website!) has a good introduction to it. Hopefully you can implement some of this stuff in CFX.

November 13, 2009, 12:42		#3
Julian_Maldonado New Member Julian Join Date: Mar 2009 Location: Spain Posts: 6 Rep Power: 17	Dear glen, Thanks for the info. The problem is how to implement the input waves in CFX 11. When I set the wave as senH + CosH or sen function, the problem is in the outlet, there are some reflection even with opening. The problem start with Velocity inthe inlet. No problem if there are only the wave function. But when I set the velocity the simulation crash. Do you know how to implement a wave on CFX 11 in the inlet+Velocity, for a hull simulation? best regards and Thanks J.

November 14, 2009, 06:53		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,848 Rep Power: 144	Non-reflecting boundary conditions are a major problem for CFD in general, they are not easy to do. V12 does have a new non-reflecting boundary condition option (I think it is a beta option) so have a look at that. Alternately I have heard of people putting a very coarse grid at the exit connected with a GGI to the main grid. When waves hit the coarse mesh the high numerical dissipation of the coarse grid damps the waves (I have never tried this but it sounds interesting!)

November 14, 2009, 07:14		#5
Julian_Maldonado New Member Julian Join Date: Mar 2009 Location: Spain Posts: 6 Rep Power: 17	Dear Glen; Thanks again. I'll try to test it on V12. Please if you have more info or any help please don't doubt to contact me. Best regards, Julian

May 19, 2010, 06:35		#6
cfxmar Member Join Date: Aug 2009 Posts: 42 Rep Power: 17	Hello! You could try also to put a higher water viscosity at the end of the domain in order to stop waves to come back.