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COMSOL Continuous Casting Example
Posted Oct 12, 2021, 6:31 a.m. EDT Computational Fluid Dynamics (CFD), Heat Transfer, Results & Visualization Version 5.6 1 Reply
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Hello,
I have a question regarding the Volume force density equations (F_r & F_z) used in this example model:
f = (1-alpha)^2/(alpha^3+epsilon)
F_r = -f.A_mush.u
F_z = -f.A_mush.(w-v_cast)
1) Why do (w-v_cast)? I am not able to understand the physical meaning behind this 2) At a z distance of 0.6 m, alpha (liquid volume fraction) is zero and the z-velocity is 0.0016 m/s which is the same as the casting velocity. But when I plot F_z I don't see it go to zero to further along the z-direction. According to the above equation shouldn't it be zero?
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Hi,
The casting is continuous hence the solidified part is having a constant velocity downstream while it is not moving in the transverse direction. Hence in the solid part we expect u = v = 0 and w=v_cast.
A fluid flow equation is solved for the liquid and solid parts. In order to mimic the translation of a rigid body in the solid part, a volumetric force is added. The term F_z=-fA.mush.(w-vcast) penalizes any solution where w is different from vcast in the solid part. The larger fA is, the smaller the difference between w and vcast can be in the solid part for a converged solution.
With best regards,
Nicolas, COMSOL