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Melting model in fluent

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Old   May 5, 2014, 08:50
Post Melting model in fluent
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I am simulating melting of paraffin wax in an enclosure with heat supplied from bottom (VOF active), all other walls adiabatic. Temperature, density and liquid fraction contours are as intended but i am getting velocity in solid regions and even in liquid region velocity is messed up. I am using viscosity and density functions as udf and gravity is turned on.

I would be grateful if someone could suggest the possible solution.
Please help.

Thanks
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Old   May 21, 2014, 09:58
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Nils G
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Hi,

so far you described your problem very briefly, therefore I might miss some important details.
What directly comes to my mind is that you might have a density that is temperature dependent in the solid region. IMHO this does not work / cannot work / should not work. The solidification / melting module in FLUENT tries to eliminate all velocities using brute force. But Continuity is more important. If the density changes (maybe decreases during heating), the solid will "spread out" in order to conserve the mass.
In reality the shape would change, so your mesh should change to compensate that error. But as you mesh is not changing I strongly recommend using a constant density in the solid region.

Best regards
Nils
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Old   May 22, 2014, 03:28
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Marcus
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Quote:
Originally Posted by siegertyp View Post
Hi,

so far you described your problem very briefly, therefore I might miss some important details.
What directly comes to my mind is that you might have a density that is temperature dependent in the solid region. IMHO this does not work / cannot work / should not work. The solidification / melting module in FLUENT tries to eliminate all velocities using brute force. But Continuity is more important. If the density changes (maybe decreases during heating), the solid will "spread out" in order to conserve the mass.
In reality the shape would change, so your mesh should change to compensate that error. But as you mesh is not changing I strongly recommend using a constant density in the solid region.

Best regards
Nils

Hi

I agree with Nils. I just have an addition to make. With constant density you will not have any buoyancy, so consider using the bousinesq approximation. I think there could be different approaches, too. For example you could try to integrate the density change in the melting zone and assign an appropriate velocity to the solid zone to change the shape of the solid zone.

Regards
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Old   May 22, 2014, 03:44
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Nils G
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Hi,

I think the bousinesq approximation "beer" suggested might work for you.

If you got inlets that are able to compensate the increasing density, then I think you should be totally fine using a temperature dependent density in the liquid region. But, as I mentioned before, just use a constant density in the solid region.

Regards
Nils

Last edited by siegertyp; May 22, 2014 at 03:44. Reason: forgot regards
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