3D wave simulation CFX

JimG91 · February 19, 2014, 16:37

Hi,

Im using Ansys CFX to simulate 3D wave flow impacting on a buoyant hemispherical hull. The water then travels up through the hull through a series of ducts. I was wondering what is the best way to go about this simulation. I'm a new user of Ansys CFX. I've completed "free surface over a bump" and the "Buoy" tutorials but I'm not sure how a 3D simulation would work. Am I correct by creating the hull and inserting an enclosure, then meshing the part with inflation around the hull. I then set up transient analysis and created the two fluids, water and air. How should I go about creating a wave motion? Should I use a moving wall as in the 2D simulation? Or is there a different way I should go about this simulation? Any help is greatly appreciated.

ghorrocks · February 19, 2014, 16:49

Is the hull fixed, undergoes a known motion or does it float and its motion is coupled to the water?

JimG91 · February 19, 2014, 17:06

Sorry yes the hull is kept in place by cables but it is free to rock side to side (coupled with the motion of the water) which is what causes the water to travel through its ducts.

ghorrocks · February 19, 2014, 17:10

There is an example of a buoyant object on a air/water interface available from ANSYS CFX support. Contact your CFX support person and ask for the example simulation. That will be the best starting point for you.

JimG91 · February 19, 2014, 17:14

Is this the 2D "Buoy" tutorial? I've looked at that but I'm still not sure how to go about a 3D simulation, is it the exact same method?

ghorrocks · February 19, 2014, 17:15

Yes, that's it. Don't forget that CFX does not have a 2D solver. It models 2D by using a 3D simulation that is one element thick. So the example really is a 3D simulation.

JimG91 · February 19, 2014, 17:19

Ok thanks it should be exactly what I'm simulating so.

JuPa · February 20, 2014, 04:11

Later on down the line if you use the mixture model at the free surface I'd be interested to know how you calculate your interface length scale.

Fatin Ihsan · December 27, 2022, 08:18

Can you suggest me some tutorials related to this problem. I am new in CFD and trying to solve a similar this.

ghorrocks · January 2, 2023, 00:54

Have a look at the tutorials on the ANSYS Customer or Academic site: https://support.ansys.com/Home/HomePage

February 19, 2014, 16:37	3D wave simulation CFX	#1
JimG91 New Member Jim Join Date: Feb 2014 Posts: 11 Rep Power: 12	Hi, Im using Ansys CFX to simulate 3D wave flow impacting on a buoyant hemispherical hull. The water then travels up through the hull through a series of ducts. I was wondering what is the best way to go about this simulation. I'm a new user of Ansys CFX. I've completed "free surface over a bump" and the "Buoy" tutorials but I'm not sure how a 3D simulation would work. Am I correct by creating the hull and inserting an enclosure, then meshing the part with inflation around the hull. I then set up transient analysis and created the two fluids, water and air. How should I go about creating a wave motion? Should I use a moving wall as in the 2D simulation? Or is there a different way I should go about this simulation? Any help is greatly appreciated.

February 19, 2014, 17:15		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,696 Rep Power: 143	Yes, that's it. Don't forget that CFX does not have a 2D solver. It models 2D by using a 3D simulation that is one element thick. So the example really is a 3D simulation. JimG91 likes this.

January 2, 2023, 00:54		#10
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,696 Rep Power: 143	Have a look at the tutorials on the ANSYS Customer or Academic site: https://support.ansys.com/Home/HomePage __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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February 19, 2014, 16:49		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,696 Rep Power: 143	Is the hull fixed, undergoes a known motion or does it float and its motion is coupled to the water?

February 19, 2014, 17:06		#3
JimG91 New Member Jim Join Date: Feb 2014 Posts: 11 Rep Power: 12	Sorry yes the hull is kept in place by cables but it is free to rock side to side (coupled with the motion of the water) which is what causes the water to travel through its ducts.

February 19, 2014, 17:10		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,696 Rep Power: 143	There is an example of a buoyant object on a air/water interface available from ANSYS CFX support. Contact your CFX support person and ask for the example simulation. That will be the best starting point for you.

February 19, 2014, 17:14		#5
JimG91 New Member Jim Join Date: Feb 2014 Posts: 11 Rep Power: 12	Is this the 2D "Buoy" tutorial? I've looked at that but I'm still not sure how to go about a 3D simulation, is it the exact same method?

February 19, 2014, 17:19		#7
JimG91 New Member Jim Join Date: Feb 2014 Posts: 11 Rep Power: 12	Ok thanks it should be exactly what I'm simulating so.

February 20, 2014, 04:11		#8
JuPa Senior Member Mr CFD Join Date: Jun 2012 Location: Britain Posts: 361 Rep Power: 14	Later on down the line if you use the mixture model at the free surface I'd be interested to know how you calculate your interface length scale.

December 27, 2022, 08:18		#9
Fatin Ihsan New Member Fatin Ihsan Join Date: Oct 2022 Posts: 2 Rep Power: 0	Can you suggest me some tutorials related to this problem. I am new in CFD and trying to solve a similar this.