Material interfaces

The material interfaces are used to represent and track the position of various interfaces on fixed grids. Typical examples include free surface, evolving interface between two materials, etc. Available representations include:

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

• LEPlic- representation based on Volume-Of-Fluid approach; the initial distribution of VOF fractions should be specified for each element (see element manual)
  

  [refvol #(rn)]

  
  
  • parameter refvol allows to set initial volume of reference fluid, then the reference volume is computed in each step and printed, so the accuracy and mass conservation can be monitored.
• LevelSet- level set based representation
  

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

  
  
  • levelset allows to specify the initial level set values for all nodes directly. The size should be equal to total number of nodes within the domain.
  • Parameters refmatpolyx and refmatpolyy allow to initialize level set by specifying interface geometry as 2d polygon. Then polygon describes the initial zero level set, and level set values are then defined as signed distance from this polygon. Positive values are on the left side when walking along polygon. The parameter refmatpolyx specifies the x-coordinates of polygon vertices, parameter refmatpolyy y-corrdinates. Please note, that level set must be initialized, either using levelset parameter or using refmatpolyx and refmatpolyy.
  • Parameter lsra allows to select level set reinitialization algorithm. Currently supported values are 0 (no re-initialization), 1 (re-initializes the level set representation by solving $d_{\tau} = S(\phi)(1-\vert\boldsymbol{\nabla}d\vert)$ to steady state, default), 2 (uses fast marching method to build signed distance level set representation).
  • Parameters rdt rerr are used to control reinitialization algorithm for lsra = 0. rdt allows to change time step of integration algorithm and parameter rerr allows to change default error limit used to detect steady state.