• Solver Fortran File: ComputeEigenValues.f90
• Solver Name: ComputeEigenValues
• Required Output Variable(s): default is EigenStress (else in EigenValue Variable Name)
• Required Input Variable(s): A tensor in Tensor Variable Name
• Optional Output Variable(s): EigenVector1, EigenVector2 and EigenVector3
• Optional Input Variable(s): None

The aim of this solver is to compute the eigenvalues of a tensor variable (e.g., strain-rate or stress tensors). Optionnaly, the 3 eigenvectors corresponding to each of the three eigenvalues can be computed.

The required keywords in the SIF file for this solver are:

Solver 3
  Equation = "EigenSR"
  Variable = -nooutput dumy
  Variable DOFs = 1

  Procedure = "ElmerIceSolvers" "ComputeEigenValues"

! 3 Eigenvalues    
  Exported Variable 1 = "EigenSR"
  EigenValue Variable Name = String "EigenSR"
  Tensor Variable Name = String "StrainRate"
  Exported Variable 1 DOFS = 3

! Principal vectors (optional) 
  Exported Variable 2 = EigenVector1
  Exported Variable 2 DOFS = 3
  Exported Variable 3 = EigenVector2
  Exported Variable 3 DOFS =  3
  Exported Variable 4 = EigenVector3
  Exported Variable 4 DOFS = 3
End

An example in which the eigenvalues and eigenvectors of the strain-rate tensor are computed can be found here [ELMER_TRUNK]/elmerice/examples/Test_StrainRate.