refactor(swf-zdg): clean up flow calculation

src/Model/SurfaceWaterFlow/swf-zdg.f90

@@ -64,7 +64,7 @@ module SwfZdgModule
  ! -- methods for time series
  procedure, public :: bnd_rp_ts => zdg_rp_ts
  ! -- private
- procedure, private :: get_cond
+ procedure, private :: qcalc
  end type SwfZdgType
 
 contains
@@ -315,7 +315,6 @@ subroutine zdg_cf(this)
  real(DP) :: qeps
  real(DP) :: absdhdxsq
  real(DP) :: depth
- real(DP) :: cond
  real(DP) :: derv
  real(DP) :: eps
  real(DP) :: range = 1.d-6
@@ -344,14 +343,11 @@ subroutine zdg_cf(this)
  depth = depth * smooth_factor
 
  ! -- calculate unperturbed q
- ! TODO: UNITCONV?!
- cond = this%get_cond(i, depth, absdhdxsq, this%unitconv)
- q = -cond * this%slope(i)
+ q = -this%qcalc(i, depth, this%unitconv)
 
  ! -- calculate perturbed q
  eps = get_perturbation(depth)
- cond = this%get_cond(i, depth + eps, absdhdxsq, this%unitconv)
- qeps = -cond * this%slope(i)
+ qeps = -this%qcalc(i, depth + eps, this%unitconv)
 
  ! -- calculate derivative
  derv = (qeps - q) / eps
@@ -365,47 +361,34 @@ subroutine zdg_cf(this)
  return
  end subroutine zdg_cf
 
- !> @brief Calculate conductance-like term
+ ! !> @brief Calculate flow
  !!
- !! Conductance normally has a dx term in the denominator
- !! but that is not included here, as the flow is calculated
- !! using Q = C * slope. The returned c value from this
- !! function has dimensions of L3/T.
- !!
- !<
- function get_cond(this, i, depth, absdhdxsq, unitconv) result(c)
- ! -- modules
- ! -- dummy
+ !! Calculate volumetric flow rate for the zero-depth gradient
+ !! condition. Flow is positive.
+ ! !<
+ function qcalc(this, i, depth, unitconv) result(q)
+ ! dummy
  class(SwfZdgType) :: this
  integer(I4B), intent(in) :: i !< boundary number
  real(DP), intent(in) :: depth !< simulated depth (stage - elevation) in reach n for this iteration
- real(DP), intent(in) :: absdhdxsq !< absolute value of simulated hydraulic gradient
  real(DP), intent(in) :: unitconv !< conversion factor for roughness to length and time units of meters and seconds
- ! -- local
+ ! return
+ real(DP) :: q
+ ! local
  integer(I4B) :: idcxs
- real(DP) :: c
  real(DP) :: width
  real(DP) :: rough
  real(DP) :: slope
- real(DP) :: roughc
- real(DP) :: a
- real(DP) :: r
  real(DP) :: conveyance
- !
+
  idcxs = this%idcxs(i)
  width = this%width(i)
  rough = this%rough(i)
  slope = this%slope(i)
- roughc = this%cxs%get_roughness(idcxs, width, depth, rough, &
- slope)
- a = this%cxs%get_area(idcxs, width, depth)
- r = this%cxs%get_hydraulic_radius(idcxs, width, depth, area=a)
-
- !conveyance = a * r**DTWOTHIRDS / roughc
  conveyance = this%cxs%get_conveyance(idcxs, width, depth, rough)
- c = conveyance / absdhdxsq
+ q = conveyance * slope**DHALF * unitconv
 
- end function get_cond
+ end function qcalc
 
  !> @ brief Copy hcof and rhs terms into solution.
  !!