Additional Variable

blade_CFX · August 4, 2013, 05:03

Hi everyone.
I am modeling a gas-water free surface flow useing CFX-14. I have created a additional variable and the source exist in the water phase. The additional variable should only exist in the water phase,but finally I found it spread into the air phase, and this is not what I want.
How can I solve this problem?If anyone know the answer,please help me.I will be very grateful to you

ghorrocks · August 4, 2013, 07:00

What type of additional variable is it (what equation did you select to model it)?

Physically, why doesn't it spread to the air phase?

Wouldn't a diffusivity (assuming it is a diffusive AV, I am just guessing here) which has a value in the liquid but is zero (or close to it, like 1e-20) in air do the trick?

blade_CFX · August 4, 2013, 07:36

Quote:

Originally Posted by ghorrocks

What type of additional variable is it (what equation did you select to model it)?

Physically, why doesn't it spread to the air phase?

Wouldn't a diffusivity (assuming it is a diffusive AV, I am just guessing here) which has a value in the liquid but is zero (or close to it, like 1e-20) in air do the trick?

The type of additional variable is specific scalar and when the air.vf>0.5,the source will be 0. The transport type in water phase is Transport Equation,and in air phase,the transport equation is off.
The additional variable can be seen as a kind of chemical substances,and it can only exist in liquid phase.

ghorrocks · August 4, 2013, 08:24

How is it spreading into the air? Can you post an image? Or show a conservation balance?

August 4, 2013, 05:03	Additional Variable	#1
blade_CFX New Member Ding Chao Join Date: Aug 2013 Posts: 5 Rep Power: 13	Hi everyone. I am modeling a gas-water free surface flow useing CFX-14. I have created a additional variable and the source exist in the water phase. The additional variable should only exist in the water phase,but finally I found it spread into the air phase, and this is not what I want. How can I solve this problem?If anyone know the answer,please help me.I will be very grateful to you

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August 4, 2013, 07:00		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	What type of additional variable is it (what equation did you select to model it)? Physically, why doesn't it spread to the air phase? Wouldn't a diffusivity (assuming it is a diffusive AV, I am just guessing here) which has a value in the liquid but is zero (or close to it, like 1e-20) in air do the trick?

August 4, 2013, 08:24		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	How is it spreading into the air? Can you post an image? Or show a conservation balance?