SetNumberOfVariables_LinearEuler3D_t Subroutine

  subroutine SetNumberOfVariables_LinearEuler3D_t(this)
    implicit none
    class(LinearEuler3D_t),intent(inout) :: this

    this%nvar = 7
    ! Only the first four variables (u, v, w, P) are advanced in time. The
    ! fifth, sixth and seventh variables - the sound speed c, the background
    ! density rho0, and the relaxation rate sigma - are spatially-varying but
    ! time-constant background fields: their flux and source are identically
    ! zero, so they are excluded from time integration rather than stepped to
    ! a no-op.
    this%nstepped = 4

  endsubroutine SetNumberOfVariables_LinearEuler3D_t