[mosef]

Hey,
I'm simulating the melting and solidification of a spherical capsule (2D), which is filled with paraffin.
I'm using an Implicit unsteady model.
The simulation works and the solution looks quiet good, BUT:
When I simulate the Melting-process, the paraffin should sink to the bottom of the capsule. In my simulation the paraffin stays in the mid until it is totally molten. I can't understand this, because the density of the solid paraffin is higher than the density of the molten praffin.
Additionally I set -9,81m/s^2 in the Gravity properties (reference values).
So why 'stays' the paraffin in the middle of the capsule?
Can someone help me?
Thx a lot!

[me3840]

Make sure you've set the reference density correctly.

[mosef]

Ok, I set the density for the liquid (780kg/m³) and the solid (830kg/m³) phase in the physic models.
I have a reference density of 1,0 kg/m³.
Hm, I don't really know how to specify this value.
What does the reference density tell me?
thx for help. I'm a newbie in STAR cmm+
:/

[me3840]

The reference density is used in the calculation for buoyancy. Take a look at the user guide, it shows the equations in there. You should either set it to zero or to the density of the lighter phase, but generally that's for fluids with two very different densities.

[mosef]

I set the reference density to zero now. But it seems, that this was not the problem. The paraffin still does not sink to the bottom. :/
Any other ideas?

[me3840]

Do you have the flow-stop volume fraction set to 1.1? Do you have the viscosity for the material set correctly?

[mosef]

I'll check this tomorrow.
If u want, I can send u the .sim-file?!

[me3840]

I won't have time to look over it, sorry.

[mosef]

Ok, no problem. I try to find the problem tomorrow

[mosef]

Hm. My Volume Fraction was set to [1.0]
I made a function for the viscosity.

[me3840]

Wait, how is there only one volume fraction in your model? You should have two, one for each phase.

[mosef]

Do u mean under EulerianPhase, I need 2 Phases?
One for 'paraffin liquid' and 'paraffin solid'?!

[me3840]

No, sorry, I was just confused, it's been a long day already.

I would still check the flow stop volume fraction though.

[mosef]

My Model is in the XY-plane. If I set the gravity now to [0.0,-9.81,0.0]m/s^2, is that rigth? Because if I set the gravity to [0.0,+9.81,0.0]m/s^2, the paraffin sinks to the bottom!

You can see the Flow-stop function in the appendix

[me3840]

You need to set the gravity vector depending on the orientation of your model in space.

[mosef]

I know, but then, if I set the gravity vector in -y Direction, the paraffin doesn't sink. It's very weird.
I set the vector with the wrong sign and it simulates correctly. With the correct sign it simulates not correctly. :/

[me3840]

You need to look at the relative solid volume fraction, what does that say?

[mosef]

I don't know whats the problem...The physic models are correct, the initial conditions also. The density is higher in the solid phase, I set a gravity vector. The Melting-Solidification flow stop is also correct...I just don't understand this
But now I think I finish this simulation. It make no sense....
Thanks so much for your help. I don't wanna waste your time.



P.S.: Blue line -> Solidification; Red line -> Melting

[khan223]

Hello, good people I am facing difficulty while doing a vof simulation tutorial in freezing water ducts. I cant find the melting solidification flow stop option. However its getting trouble for me not to complete the tutorial.

[cwl]

Tutorial around the page 10073 "VOF: Melting-Solidification" should help.