[ZiadElSayed]

Hello everyone,

I am working on a solidification model fro Aluminium alloy, the thing is, I am supposed to have an air gap between the top wall of the mould and the molten aluminium before solidification. The shape of the mould is cylindrical, nothing complex. I have been trying to account for the air gap to see the effect on the final products geometry due to solidification. However, I am not calculate the air gap, I found in the manual that assigning contact resistance is the way to do this but I am not sure how to calculate it, can anyone help me with this?

I attached a simple schematic of the mould, aluminium, and air gap.

Thank you in advance.

[MKuhn]

I think it is different. The air gap is between the aluminum and the mould, and not on the top of the aluminum. Then the contact resistance is: thermal conductivy of air / thickness of the air gap.

[ZiadElSayed]

Originally Posted by MKuhn

I think it is different. The air gap is between the aluminum and the mould, and not on the top of the aluminum. Then the contact resistance is: thermal conductivy of air / thickness of the air gap.

Okay, thank you, I’ll try that and let you know how it went. By the way, to visualize the air gap do I draw a contour of the mass fraction of Aluminium? I am not using multiphase modeling as I am only interested in the solidification.

[MKuhn]

The mass fraction has nothing to do with the air gap. Mass fraction means the proportion between liquid and solid aluminium, and the mass fraction rate means how much aluminium will solidifiacte in time.

[ZiadElSayed]

Originally Posted by MKuhn

The mass fraction has nothing to do with the air gap. Mass fraction means the proportion between liquid and solid aluminium, and the mass fraction rate means how much aluminium will solidifiacte in time.

Okay, so is there any way to visualize the air gap while not using multiphase modeling?

[MKuhn]

Originally Posted by ZiadElSayed

Okay, so is there any way to visualize the air gap while not using multiphase modeling?

No, as they are no cells inside the gap, no flow will be simulated. You see only two different temperatures on the wall between the aluminium and the mould, due to the thermal resistance.