[Gfs-devel] about VOF (single phase advection without velocity extension)

[Ruhollah T. <ro...@gm...>]

Hi,


Assume our surface is implicitly represented by VOF field, and assume we
have just velocity field on surface (in gerris, in center of area of
reconstructed planar interface), so, to use classic VOF method we need
velocity extension to whole domain, or specifically, in my application near
interface, as my interface evolves just from it boundaries (there is no
nucleation of void within domain)


But, it seems that it is possible to use semi-lagrangian split VOF method
which is available in gerris (Zaleski JCP99 paper) without velocity
extension.


Assume advection in x-direction and assume advection of an interfacial cell
(internal cells are not important for me). Based on Zaleski paper (JCP 99),
we use linear interpolation of x-component of velocity in the cell (equation
16 of paper), I think that to avoid extension of velocity, we can use
available velocity (at center of area of surface cell) as fixed velocity
(u=u0, u0 is available velocity in center of area of surface cell), I mean
that method as constant extrapolation of velocity. Then we do the same for
other directions (of course after each split advection we may have new
surface cells and for them we use advected velocity, weighted average on
input fluxes)


What is your idea about this method, can it works? Do you recommend
extension of velocity (note that in my case we do not have physical
constraint for extension, except feasibility of extension along interface
normal).


Best regards

RT