# GfsVariableTracerVOF

### From Gerris

*Note that this implementation of VOF tracers has been replaced by GfsVariableTracerVOFHeight and will become obsolete. In particular, GfsVariableTracerVOFHeight combined with GfsVariableCurvature should give consistent interface curvature estimates for parallel simulations. This is not the case for GfsVariableTracerVOF.*

A GfsVariableTracerVOF defines a volume-fraction field advected using the geometrical Volume-Of-Fluid technique.

The syntax in parameter files is:

[ GfsVariableTracer ]

Whenever a new GfsVariableTracerVOF is created called `T`

for example, four additional variables (three in 2D) are automatically created:

`T_x`

- the x-component of the normal to the interface,
`T_y`

- the y-component of the normal to the interface,
`T_z`

- the z-component of the normal to the interface (3D only),
`T_alpha`

- the value such that the normalised equation of the interface in a given cell is given by
`T_x*x + T_y*y + T_z*z = T_alpha`

.

The interfacial area (length in 2D) per unit volume (area in 2D) can be computed within a GfsFunction using the predefined `area()`

function. For example

GfsOutputScalarSum { istep = 1 } area { v = area("T") }

with `"T"`

the name of a **GfsVariableTracerVOF** will compute the time evolution of the total interface area (length in 2D).

### Examples

VariableTracerVOF {} T

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VariableTracerVOF T

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VariableTracerVOF Ti

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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VariableTracerVOF T

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