2 Phase flow in CFX?

Cipherflak · May 31, 2012, 17:59

Hello!

I have this problem I've been looking at with a large underwater tank of LNG (of some kind) that erupts, causing the liquid to boil and seep from the tank while water is pressing into the tank. The goal is to find out how fast the tank is emptied of LNG.

Can CFX handle 2-phase flows, i.e., the transition from liquid to gas at temperature changes, etc? If not, just normal liquid mixing would be an interesting scenario to try out. Anyone done something similar?

ghorrocks · May 31, 2012, 18:55

Yes, CFX can model this. But it is quite a difficult model with lots of complex physics going on. It will take a while to set up and validate/verify.

Cipherflak · June 2, 2012, 03:07

Thanks! Good to hear. I will try to go ahead and see what I can make out of this, complex as it is.
If anyone have any tips or heads-up on the setup, I'd be grateful!

ghorrocks · June 2, 2012, 06:32

My big tip is to start simple (eg ideal gas) and get that working before going to real gas properties. Also develop the physics one model at a time - so a simple test case to get the compressible flow working, then another one just looking at the boiling of LNG, then a third model just looking at the water LNG mixing (with no boiling). Don't forget to validate and verify these simple models, either to experimental results or analytical solutions. When all these simpler models are working by themselves only then should you start combining them together into the final simulation.

Cipherflak · June 4, 2012, 03:12

Yes that sounds reasonable. Thanks! The more I think about it I realize how complex this problem really is.

One practical question about CFX, though. I've done a few simulations in CFX earlier, but that was always with specific inlets and outlets. How do you specify a pool, with the extent and properties of the liquid?

ghorrocks · June 4, 2012, 03:15

This is all in the initial conditions.

May 31, 2012, 17:59	2 Phase flow in CFX?	#1
Cipherflak New Member John E Join Date: Oct 2011 Posts: 11 Rep Power: 14	Hello! I have this problem I've been looking at with a large underwater tank of LNG (of some kind) that erupts, causing the liquid to boil and seep from the tank while water is pressing into the tank. The goal is to find out how fast the tank is emptied of LNG. Can CFX handle 2-phase flows, i.e., the transition from liquid to gas at temperature changes, etc? If not, just normal liquid mixing would be an interesting scenario to try out. Anyone done something similar?

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May 31, 2012, 18:55		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Yes, CFX can model this. But it is quite a difficult model with lots of complex physics going on. It will take a while to set up and validate/verify.

June 2, 2012, 03:07		#3
Cipherflak New Member John E Join Date: Oct 2011 Posts: 11 Rep Power: 14	Thanks! Good to hear. I will try to go ahead and see what I can make out of this, complex as it is. If anyone have any tips or heads-up on the setup, I'd be grateful!

June 2, 2012, 06:32		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	My big tip is to start simple (eg ideal gas) and get that working before going to real gas properties. Also develop the physics one model at a time - so a simple test case to get the compressible flow working, then another one just looking at the boiling of LNG, then a third model just looking at the water LNG mixing (with no boiling). Don't forget to validate and verify these simple models, either to experimental results or analytical solutions. When all these simpler models are working by themselves only then should you start combining them together into the final simulation.

June 4, 2012, 03:12		#5
Cipherflak New Member John E Join Date: Oct 2011 Posts: 11 Rep Power: 14	Yes that sounds reasonable. Thanks! The more I think about it I realize how complex this problem really is. One practical question about CFX, though. I've done a few simulations in CFX earlier, but that was always with specific inlets and outlets. How do you specify a pool, with the extent and properties of the liquid?

June 4, 2012, 03:15		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	This is all in the initial conditions.