distinguish water and ice phases

valio · July 19, 2012, 15:28

Hi everyone,

I'm working about 3D melting problem on fluent software.
I got the result of the simulation and for analyse I would like to measure the mass or volume of melting water
The problem is I need to distinguish water and ice, but i don't know how i can do it.

If you got an idea, let me know

Thank you
Valio

flotus1 · July 19, 2012, 16:24

The "liquid fraction" is the variable you are serching for.

liquid fraction=1 -> Water
liquid fraction=0 -> Ice

valio · July 20, 2012, 01:11

first of all, thank you for your answer.

But as I work with water, it is a pure substance so Tliquidus = Tsolidus = melting temperature and the liquid fraction definition is : Beta=( T- T(solidus))/(T(liquidus)-T(solidus))
so, beta is not define so I can't use liquid definition.

I still got a distinguish problem. Have you an other idea to find a solution ?

flotus1 · July 20, 2012, 02:34

I am also working with pure substances right now.
In this case, the liquid fraction is based on enthalpy. So it is still a variable to distinguish the solid and liquid phase and is well-defined even for pure substances.

valio · July 20, 2012, 13:59

So I don't need to give information about the solidus and liquidus temperature ?

flotus1 · July 20, 2012, 17:40

Sure you need the two temperatures. The fluent manual tells you that you can model a pure substance just by entering two identical values for solidus and liquidus temperature.

Now imagine you heat the solid up to the liquidus temperature (which equals solidus). From now on, the liquid fraction is computed based on the enthalpy.
Lets say the enthalpy of fusion is 100 J/kg and at a certain time, we already put 40 J/kg of heat into the material at a constant temperature, then the liquid fraction is 0.4.

valio · July 20, 2012, 19:29

Yes, I agree with all you say.
So I launched a simulation with Tsolidus=Tliquidus=273.15K
After computational, I get these results

Temperature profil seems good, but the liquid fraction seems not good so I can't determine the volume of liquid fraction.

I don't know what stop me to figure out the right liquid fraction profile

flotus1 · July 20, 2012, 19:59

This is really odd.
I ran lots of simulations with melting of a pure substance in fluent.
The liquid fraction was in excellent agreement with the temperature.

I can only assume that there is something wrong with your setup.

July 19, 2012, 15:28	distinguish water and ice phases	#1
valio New Member Esteban Join Date: Jul 2012 Posts: 13 Rep Power: 14	Hi everyone, I'm working about 3D melting problem on fluent software. I got the result of the simulation and for analyse I would like to measure the mass or volume of melting water The problem is I need to distinguish water and ice, but i don't know how i can do it. If you got an idea, let me know Thank you Valio

July 20, 2012, 17:40		#6
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,427 Rep Power: 49	Sure you need the two temperatures. The fluent manual tells you that you can model a pure substance just by entering two identical values for solidus and liquidus temperature. Now imagine you heat the solid up to the liquidus temperature (which equals solidus). From now on, the liquid fraction is computed based on the enthalpy. Lets say the enthalpy of fusion is 100 J/kg and at a certain time, we already put 40 J/kg of heat into the material at a constant temperature, then the liquid fraction is 0.4. mroue likes this. Last edited by flotus1; July 20, 2012 at 18:25.

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July 19, 2012, 16:24		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,427 Rep Power: 49	The "liquid fraction" is the variable you are serching for. liquid fraction=1 -> Water liquid fraction=0 -> Ice

July 20, 2012, 01:11		#3
valio New Member Esteban Join Date: Jul 2012 Posts: 13 Rep Power: 14	first of all, thank you for your answer. But as I work with water, it is a pure substance so Tliquidus = Tsolidus = melting temperature and the liquid fraction definition is : Beta=( T- T(solidus))/(T(liquidus)-T(solidus)) so, beta is not define so I can't use liquid definition. I still got a distinguish problem. Have you an other idea to find a solution ?

July 20, 2012, 02:34		#4
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,427 Rep Power: 49	I am also working with pure substances right now. In this case, the liquid fraction is based on enthalpy. So it is still a variable to distinguish the solid and liquid phase and is well-defined even for pure substances.

July 20, 2012, 13:59		#5
valio New Member Esteban Join Date: Jul 2012 Posts: 13 Rep Power: 14	So I don't need to give information about the solidus and liquidus temperature ?

July 20, 2012, 19:59		#8
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,427 Rep Power: 49	This is really odd. I ran lots of simulations with melting of a pure substance in fluent. The liquid fraction was in excellent agreement with the temperature. I can only assume that there is something wrong with your setup.