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Velocity on Free Surface Boundary

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Old   July 29, 2001, 11:44
Default Velocity on Free Surface Boundary
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Lin F.F
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Who can give me some give directions about boundary condition for free surface.

I has writen a 3-D free surface code with VOF methods. There are some similarity between my code and NASA-VOF3D.

But in NASA-VOF3D, boundary condition for free surface is very coarse for velocity. There are spurious velocity components that we occasionally observed in NASA-VOF3D code.

Also, I think that the cell's velocity divergence may not actually be driven to zero, for there are not satisfy for free surface cell. But it's base for NASA-VOF3D and other codes.

What's your opinion?

Thanks!
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Old   August 2, 2001, 14:06
Default Re: Velocity on Free Surface Boundary
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Patrick Godon
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Hi,

By free surface, do you mean open boundary conditions? Or by free surface, do you mean the surface of a liquid?

In the case of an open boundary conditions, you should use the method of characteristics to impose the conditions, and you should not overspecify any variables.

For the treatment of the surface of fluid, I know only the shallow water approximation for the study of surface waves.

Patrick
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Old   August 3, 2001, 03:27
Default Re: Velocity on Free Surface Boundary
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Herve
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I think there might be a 1998 paper by Tachmen and Kahawita on this sort of issue with related mesh adaption solutions for channel flows. But it is quite difficult to determine since at such interface, at the wall boundary, the velocity can be found to be very high, and if they are directly applied to the free surface the simulation quickly become unstable.
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Old   August 4, 2001, 11:30
Default Re: Velocity on Free Surface Boundary
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Lin F.F
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Thanks,

My code is for one fluid as liquid. Free surface on liquid, such as mold filling.
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