Learning Forum

[axt5488]

[axt5488]

Hello
Does anybody know or has an idea why melting does not occur even temperature exceeds melting point/

[DrAmine]

Moving Heat Source: You can create an Expression to mimic a moving heat source which will change where it applies on time. If you know how the source will move then it should be simple. (Alternative is to use UDF).
Can you just show the VOF field without showing the grid. How many cell zones do you have?

[axt5488]

Thank you Dr Amine
VOF model is not on in this simulation. This is the image that I have when I plot the contour for liquid fraction after running only Solidification & Melting with Energy 'on'. Also the heat source is not moving just defined the heat flux in Cell Zone and Wall to see and understand the solidification and melting basics. I start with very basic to understand the melting simulation since there is only one case in ansys fluent tutorial and the parameters in that case are not fully explained. I do not know why the image is look like this (grid). Interior air always liquid fraction 1.0 in every case but there is no liquid fraction in Aluminum side.

[DrAmine]

Do you have air and "fluid" aluminum in the same cell zone? Add screenshots of all important panels of your case, please.

[axt5488]

Hello Dr Amine Here you can see
When I try to plot liquid fraction:
The result is like
When I check the temperature distribution if it exceeds melting (1150K) then the thermal gradient looks like this
When I run the simulation with VOF model on:
Properties of Liquid Aluminum


Cell Zone Condition Energy source defined as constant heat flux for pb_left and pb_right these regions can be distinguished in the temperature contour with color gradient

Boundary condition for pb_left and pb_right the other boundaries constant at 300K


Time step size defined as 0.1 which is smaller then the courant number (0.25)
Liquid volume fraction is like
when I change the surface tension coefficient from -0.0036 (this value given in the ansys tutorial for marangoni stress) to 0 result does not change
If you need further info please let me know. I guess I need to clarify the definitions for fluid and solid region. For melting metal I defined as liquid aluminum. Do I need to define melting region in two groups as fluid and solid or how can I do that

[Rob]

Is it supposed to be one fluid zone? If so there are a lot of walls. How many fluid zones are there, and what are the boundaries between them?

[axt5488]

Hello Rob there are two fluid regions: air at the top surface and the melting metal you can see the image below

[DrAmine]

You said you do not have multiphase and now I see VOF.
The mass transfer between phases is wrong: u do not require that.

[axt5488]

Dr Amine as mentioned in the first post VOF is not "on" I just want to show you what is changed when I turned it on.
Here again you can see without VOF

When I check the density of the region it seems there is no phase change and has the density of liquid metal.

[Rob]

And you have walls between the air and melting fluid? If so the liquid/solid fraction in the air space may return an odd value so check any liquidus/solidus temperatures in that zone: it may return as all liquid due to the model definitions.

[axt5488]

Hello Rob
I have walls between air and melting fluid to define convection and radiation at the boundary condition.
Do you mean to check the defined liquidus / solidus temperature?

[Rob]

What did you do to those walls? Ie please confirm they're still coupled.

[axt5488]

Walls used to define heat transfer conditions between the regions.
I think the problem is the definition of the cell zone condition when it is defined as fluid the volume fraction of the interior resulted as 1.0 if it is defined as solid then result was 0.0. Is there a way to define the cell zone condition as mixture?

[Rob]

If the cell zone is fluid it'll need to be assigned as the correct material. If the metal and air are separate you don't need a multiphase model, and then set the two fluid zones as air & molten metal.