CentralDifferenceScheme.f90

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module centraldifferenceschememodule
  use kindmodule, only: dp, i4b
  use constantsmodule, only: dhalf, done
  use interpolationschemeinterfacemodule, only: interpolationschemeinterface, &
                                                coefficientstype
  use basedismodule, only: disbasetype
  use tspfmimodule, only: tspfmitype
 
  implicit none
  private
 
  public :: centraldifferenceschemetype
 
  type, extends(interpolationschemeinterface) :: centraldifferenceschemetype
    private
    class(disbasetype), pointer :: dis
    type(tspfmitype), pointer :: fmi
    real(dp), dimension(:), pointer :: phi
  contains
    procedure :: compute
    procedure :: set_field
  end type centraldifferenceschemetype
 
  interface centraldifferenceschemetype
    module procedure constructor
  end interface centraldifferenceschemetype
 
contains
  function constructor(dis, fmi) result(interpolation_scheme)
    ! -- return
    type(centraldifferenceschemetype) :: interpolation_scheme
    ! --dummy
    class(disbasetype), pointer, intent(in) :: dis
    type(tspfmitype), pointer, intent(in) :: fmi
 
    interpolation_scheme%dis => dis
    interpolation_scheme%fmi => fmi
 
  end function constructor
 
  !> @brief Set the scalar field for which interpolation will be computed
  !!
  !! This method establishes a pointer to the scalar field data for
  !! subsequent central difference interpolation computations.
  !<
  subroutine set_field(this, phi)
    ! -- dummy
    class(centraldifferenceschemetype), target :: this
    real(DP), intent(in), dimension(:), pointer :: phi
 
    this%phi => phi
  end subroutine set_field
 
  function compute(this, n, m, iposnm) result(phi_face)
    !-- return
    type(coefficientstype) :: phi_face
    ! -- dummy
    class(centraldifferenceschemetype), target :: this
    integer(I4B), intent(in) :: n
    integer(I4B), intent(in) :: m
    integer(I4B), intent(in) :: iposnm
    ! -- local
    real(dp) :: lnm, lmn, omega
 
    ! -- calculate weight based on distances between nodes and the shared
    !    face of the connection
    if (this%dis%con%ihc(this%dis%con%jas(iposnm)) == 0) then
      ! -- vertical connection; assume cell is fully saturated
      lnm = dhalf * (this%dis%top(n) - this%dis%bot(n))
      lmn = dhalf * (this%dis%top(m) - this%dis%bot(m))
    else
      ! -- horizontal connection
      lnm = this%dis%con%cl1(this%dis%con%jas(iposnm))
      lmn = this%dis%con%cl2(this%dis%con%jas(iposnm))
    end if
 
    omega = lmn / (lnm + lmn)
 
    phi_face%c_n = omega
    phi_face%c_m = done - omega
 
  end function compute
 
end module centraldifferenceschememodule