GfsInitFraction

From Gerris

GfsInitFraction is used to initialise a volume-fraction field from a given surface (typically the shape of an interface to be represented using a Volume-Of-Fluid formulation).

The syntax in parameter files is:

[ GfsGenericInit ] V [ GfsSurface ]

where V is a GfsVariable.

If GfsSurface is defined implicitly, by convention the volume fraction of cells not cut by the interface is set to one if the implicit function is positive and zero otherwise.

Examples

• Rayleigh-Taylor instability

  InitFraction {} T (0.05*cos (2.*M_PI*x) + y) { ty = 0.5 }

• Air-water flow around a Series 60 cargo ship

    InitFraction T (1e-4 - z)

• Time-reversed VOF advection in a shear flow

    InitFraction T (ellipse (0, -.236338, 0.2, 0.2))

    InitFraction { start = end } Tref (ellipse (0, -.236338, 0.2, 0.2))

• Time-reversed advection with curvature-based refinement

    InitFraction T (ellipse (0, -.236338, 0.2, 0.2))

    InitFraction { start = end } Tref (ellipse (0, -.236338, 0.2, 0.2))

• Mass conservation

    InitFraction T (- ellipse (0, 0.3, 0.1, 0.1))

    InitFraction T1 (- ellipse (0, 0.3, 0.1, 0.1))

• Mass conservation with solid boundary

    InitFraction T (- ellipse (-0.2, 0., 0.05, 0.05))

    InitFraction T1 (- ellipse (-0.2, 0., 0.05, 0.05))

• Momentum conservation for large density ratios

    InitFraction T (- ellipse(-0.3,0,radius,radius))

• Circular droplet in equilibrium

  InitFraction T CIRCLE

• Axisymmetric spherical droplet in equilibrium

  InitFraction T CIRCLE

• Planar capillary waves

  InitFraction T (y - 0.01*cos (2.*M_PI*x))

• Air-Water capillary wave

  InitFraction T (y - 0.01*cos (2.*M_PI*x))

• Fluids of different densities

  InitFraction T (y - 0.01*cos (2.*M_PI*x))

• Pure gravity wave

  InitFraction {} T (y - 0.01*cos (2.*M_PI*x))

• Shape oscillation of an inviscid droplet

    InitFraction T ({ x += 0.5; y += 0.5; return x*x + y*y - RADIUS(x,y)*RADIUS(x,y); })