Material interfaces

Material interfaces represent and track the position of various interfaces on fixed grids — a free surface, or an evolving interface between two materials, for example. The representation is selected by the miflag parameter of the analysis record; see Transient incompressible flow — SUPG/PSPG algorithm.

Table 8 Available material interface representations.

MI	miflag	Compatibility
LEPlic	0	2D triangular
LevelSet	1	2D triangular

LEPlic

A representation based on the Volume-Of-Fluid approach. The initial distribution of VOF fractions should be specified for each element; see the Element Library Manual.

Syntax

[refvol (rn)]

Parameters

[refvol (rn)]

Initial volume of the reference fluid. When it is given, the reference volume is computed and printed in every step, so that accuracy and mass conservation can be monitored.

LevelSet

A level-set based representation.

Syntax

(levelset (ra) | (refmatpolyx (ra) refmatpolyy (ra))) [lsra (in)] [rdt (rn)] [rerr (rn)]

Parameters

levelset (ra)

Initial level set values for all nodes, given directly. Its size should equal the total number of nodes in the domain.

refmatpolyx (ra), refmatpolyy (ra)

Alternatively, initialize the level set from the interface geometry given as a 2D polygon: the polygon describes the initial zero level set, and the level set values are then the signed distance from it, positive on the left side when walking along the polygon. refmatpolyx holds the x coordinates of the polygon vertices and refmatpolyy the y coordinates.

Important

The level set must be initialized, either with levelset or with refmatpolyx and refmatpolyy.

[lsra (in)]

Level set reinitialization algorithm: 0 no reinitialization; 1 (default) reinitializes the level set representation by solving \(d_{\tau} = S(\phi)(1-\vert\boldsymbol{\nabla}d\vert)\) to steady state; 2 uses the fast marching method to build a signed-distance level set representation.

[rdt (rn)]

Time step of the reinitialization integration algorithm used by lsra 1. Default 0.0, for which the algorithm chooses the step itself; any positive value overrides that choice.

[rerr (rn)]

Error limit used to detect the steady state of the lsra 1 reinitialization algorithm. Default 1.e-6.

[nsd (in)]

Number of spatial dimensions of the level set.

[ci1 (rn)], [ci2 (rn)]

Coefficients of the interface reconstruction.