surface tension problem when using VOF+Solidification&melting models

AlvinF · August 18, 2017, 04:16

Hi everyone,
I'm modeling the process of selective laser melting using FLUENT. I built a simple model to domenstrate my code and setting. The VOF and Solidification&Melting models are implented in my model.
Firstly, I built a model without the surface tension. I used the DEFFINE_INIT to set a cuboid space into the center of the computational domain.

The laser will irradiate the surface of the cuboid for 0.0015s and then stop irradiatting. The molten pool at 0.0015s like this:

The thermal field like this:

After solidificating, a surface will appear

But the problem is, when I add surface tension coefficients into the phase interaction dialog box of VOF, the result was ridiculous that the solid area begin to move like the picture below.

As the description in the Fluent Theory Guide, the addition of surface tension to the VOF calculation results in a source term in the momentum equation. But when we use the solidification&melting model, there is a momentum sink adding to the momentum equation. So theoretically the solid area can't move.

I really don't know how to fix it. Maybe there are other methods to model the effect of surface tension, can u tell me where the mistake is.

I am really confused for a long time, and this simulation is very important to my thesis. I really need your help. Thank you!

mohammad razzaghian · August 18, 2017, 17:26

Hi Yiqi Feng,

I am also modeling the process of selective laser melting using Ansys fluent. Make sure to use the energy model during your simulation. What boundary conditions are you using?

AlvinF · August 19, 2017, 02:06

Quote:

Originally Posted by mohammad razzaghian

Hi Yiqi Feng,

I am also modeling the process of selective laser melting using Ansys fluent. Make sure to use the energy model during your simulation. What boundary conditions are you using?

Dear friend,

Thank you for your reply. I have uesd the energy model.
The boundary condition is discribed like the picture below:

There is also a "top" wall, whose boundary condition is outflow, but it isn't showed in the picture.

mohammad razzaghian · August 21, 2017, 20:44

Hi Yiki,

What are the material phases in your VOF model? I mean what type of material are you considered for layers and substrate?

You should consider temperature dependent properties in your model.

Tharushan · April 22, 2024, 11:31

Hi Alvin, I am currently conducting a project similar to yours in which I have to perform laser cutting on a solid. However, when I conduct the simulation the heated zone bulges and does not melt. Is there any settings that has to be enabled or altered for me to be able to observe the molten pool?

August 18, 2017, 04:16	surface tension problem when using VOF+Solidification&melting models	#1
AlvinF New Member Yiqi Feng Join Date: Jul 2017 Location: China Posts: 5 Rep Power: 9	Hi everyone, I'm modeling the process of selective laser melting using FLUENT. I built a simple model to domenstrate my code and setting. The VOF and Solidification&Melting models are implented in my model. Firstly, I built a model without the surface tension. I used the DEFFINE_INIT to set a cuboid space into the center of the computational domain. The laser will irradiate the surface of the cuboid for 0.0015s and then stop irradiatting. The molten pool at 0.0015s like this: The thermal field like this: After solidificating, a surface will appear But the problem is, when I add surface tension coefficients into the phase interaction dialog box of VOF, the result was ridiculous that the solid area begin to move like the picture below. As the description in the Fluent Theory Guide, the addition of surface tension to the VOF calculation results in a source term in the momentum equation. But when we use the solidification&melting model, there is a momentum sink adding to the momentum equation. So theoretically the solid area can't move. I really don't know how to fix it. Maybe there are other methods to model the effect of surface tension, can u tell me where the mistake is. I am really confused for a long time, and this simulation is very important to my thesis. I really need your help. Thank you! mohammad razzaghian likes this.

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August 18, 2017, 17:26		#2
mohammad razzaghian New Member Join Date: Jul 2014 Location: USA Posts: 5 Rep Power: 12	Hi Yiqi Feng, I am also modeling the process of selective laser melting using Ansys fluent. Make sure to use the energy model during your simulation. What boundary conditions are you using?

August 21, 2017, 20:44		#4
mohammad razzaghian New Member Join Date: Jul 2014 Location: USA Posts: 5 Rep Power: 12	Hi Yiki, What are the material phases in your VOF model? I mean what type of material are you considered for layers and substrate? You should consider temperature dependent properties in your model.

April 22, 2024, 11:31		#5
Tharushan New Member Join Date: Dec 2023 Posts: 5 Rep Power: 2	Hi Alvin, I am currently conducting a project similar to yours in which I have to perform laser cutting on a solid. However, when I conduct the simulation the heated zone bulges and does not melt. Is there any settings that has to be enabled or altered for me to be able to observe the molten pool?