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Modelling Melting/Solidification

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Old   April 16, 2012, 07:25
Default Modelling Melting/Solidification
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Yang Yue
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Dear FLOW-3D users,

I know FLOW-3D can model heat transfer and solidification problem, so I was trying to run a simple model on this.

I put a simple cylinder bar (Al alloy) inside a Pyrex glass tube. The surface of the bar contacted with the interior surface of the glass tube and the top face of the bar was free surface. Then I applied a heat source on the external surface of the glass tube. The mesh contained the all objects. The objects were set to continuously heated from room temperature to the 1000 K. I set the cylinder bar as the fluid region in "Model Setup"-->"Initial".

Initially the bar was solid and the temperature gradient around the bar looked OK during heating. Once the temperature of the bar reached about 20 K above the solidus temperature of the alloy, there was convection inside some region of the bar, which was also good since part of the bar started to melt. However, when the whole body of the bar reached that temperature (not the liquidus temperature), the velocity vector inside the bar pointed to the same direction as the gravity force and in the next time step, the free surface broke up, which should be stable or showed curvature due to the surface tension.

Has anybody experienced similar problem when they run solidification module in FLOW-3D?

Thanks!

Yang
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Old   April 16, 2012, 13:25
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michael barkhudarov
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Quote:
Originally Posted by therockyy View Post
Dear FLOW-3D users,

I know FLOW-3D can model heat transfer and solidification problem, so I was trying to run a simple model on this.

I put a simple cylinder bar (Al alloy) inside a Pyrex glass tube. The surface of the bar contacted with the interior surface of the glass tube and the top face of the bar was free surface. Then I applied a heat source on the external surface of the glass tube. The mesh contained the all objects. The objects were set to continuously heated from room temperature to the 1000 K. I set the cylinder bar as the fluid region in "Model Setup"-->"Initial".

Initially the bar was solid and the temperature gradient around the bar looked OK during heating. Once the temperature of the bar reached about 20 K above the solidus temperature of the alloy, there was convection inside some region of the bar, which was also good since part of the bar started to melt. However, when the whole body of the bar reached that temperature (not the liquidus temperature), the velocity vector inside the bar pointed to the same direction as the gravity force and in the next time step, the free surface broke up, which should be stable or showed curvature due to the surface tension.

Has anybody experienced similar problem when they run solidification module in FLOW-3D?

Thanks!

Yang
Looks like you are doing all right with the heat transfer part. Sounds like pressure is initially uniform. If that's true, try initializing a hydrostatic pressure. Also, it may help to limit the time step size to smooth out the transition from pure h/t to flow in the metal.

Finally, try increasing the drag coefficient, TSDRG, from the default of 1.0, which may be too small, to something like a 1000. This will also smooth out the start of the flow in the part.
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