https://www.nic.funet.fi/pub/sci/physic ... Manual.pdf
see chapter 58, variables are U and DNU
Solver 2
Exec Solver = Afrer timestep
Equation = SaveScalars
Procedure = "SaveData" "SaveScalars"
Filename = "displacement.dat"
Variable 1 = U 3
Operator 1 = max
Variable 2 = DNU 1
Operator 1 = max
End
Equation 1
Name = "Equation 1"
Active Solvers(2) = 1 2
End