Lagrange multiplier in axial symmetry

Hey Guys,

i am modelling a moving boundary interface (Stefan Problem), using the Lagrange multiplier T_lm from heat transfer analysis for prescribed normal mesh velocity in the deformed geometry physics.

The model is almost identical to the 2D Tin melting front example from Comsol library:
www.comsol.com/model/tin-melting-front-6234
except that I work in axial symmetry and my interface is perpendicular to the axis of symmetry.

When I solve, the Lagrange multiplier T_lm is always zero at r=0. I guess I am missing something fundamental here ? Does anyone have a hint for me ?

Thank you and Regards

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Flanell

2 Replies Last Post Apr 27, 2017, 5:40 AM EDT
COMSOL Moderator

Hello Flanell

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Posted: 5 months ago Apr 18, 2017, 1:36 AM EDT
Hi Flanell,

In fact, the Lagrange multiplier T_lm should be in W/m2, but for symetric problems is in W/m. you should easily just use: T_lm [W/m^2]/(rho_Si*DelH*r*pi) instead of T_lm [W/m^2]/(rho_Si*DelH). In this case the Lagrange multiplier transfer from "per radius" to "per area (Pi*r*r*)"
Hi Flanell, In fact, the Lagrange multiplier T_lm should be in W/m2, but for symetric problems is in W/m. you should easily just use: T_lm [W/m^2]/(rho_Si*DelH*r*pi) instead of T_lm [W/m^2]/(rho_Si*DelH). In this case the Lagrange multiplier transfer from "per radius" to "per area (Pi*r*r*)"

Posted: 5 months ago Apr 27, 2017, 5:40 AM EDT
Hi Amir,

thanks alot!

I figured it out alreday and it works like you said

Best

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Flanell
Hi Amir, thanks alot! I figured it out alreday and it works like you said Best -- ______ Flanell

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