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Define a different viscosity for thin water columns #126

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1ba6e02
Increase viscosity in thin film region
cbegeman Jan 24, 2024
449e871
Add different config options for viscosity ramp
cbegeman Jan 8, 2025
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16 changes: 16 additions & 0 deletions components/mpas-ocean/src/Registry.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -1258,6 +1258,22 @@
description="If true, just zero out velocity that is contributing to drying for cell that is drying. This option can be used to estimate acceptable minimum thicknesses for a run."
possible_values=".true. or .false."
/>
<nml_option name="config_use_thin_film_viscosity" type="logical" default_value=".false."
description="If true, ramp velocities and tendencies to zero rather than applying a simple on/off switch."
possible_values=".true. or .false."
/>
<nml_option name="config_thin_film_viscosity_constant" type="real" default_value="1e-3"
description="Viscosity used in the thin film."
possible_values="Any positive real"
/>
<nml_option name="config_thin_film_viscosity_hmin" type="real" default_value="1e-3"
description="Minimum layer thickness at which viscosity is ramped toward the full value. Recommended value equal to config_drying_min_cell_height."
possible_values="Any positive real"
/>
<nml_option name="config_thin_film_viscosity_hmax" type="real" default_value="2e-3"
description="Maximum layer thickness at which viscosity is first ramped toward the full value. Recommended value equal to 2 * config_drying_min_cell_height."
possible_values="Any positive real"
/>
<nml_option name="config_zero_drying_velocity_ramp" type="logical" default_value=".false."
description="If true, ramp velocities and tendencies to zero rather than applying a simple on/off switch."
possible_values=".true. or .false."
Expand Down
55 changes: 50 additions & 5 deletions components/mpas-ocean/src/shared/mpas_ocn_vmix_cvmix.F
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Expand Up @@ -64,8 +64,9 @@ module ocn_vmix_cvmix
type(cvmix_shear_params_type) :: cvmix_shear_params
type(cvmix_tidal_params_type) :: cvmix_tidal_params

logical :: lnonzero_surf_nonlocal, cvmixOn, cvmixConvectionOn, cvmixKPPOn
real (kind=RKIND) :: backgroundVisc, backgroundDiff
logical :: cvmixOn, cvmixConvectionOn, cvmixKPPOn, thinFilmViscOn
real (kind=RKIND) :: backgroundVisc, backgroundDiff, thinFilmViscConstant, hMin, hMax, hRampFactor
real (kind=RKIND) :: thinFilmViscConstant, hMin, hMax, hRampFactor

integer :: cvmixBackgroundChoice ! user choice of cvmix background scheme

Expand Down Expand Up @@ -156,14 +157,14 @@ subroutine ocn_vmix_coefs_cvmix_build(meshPool, statePool, forcingPool, err, tim
integer, dimension(:,:), pointer :: edgesOnCell, cellsOnEdge, cellsOnCell, cellMask

integer :: k, i, iCell, iNeighbor, timeLevel, kIndexOBL, kav, iEdge, nCells
integer :: edgeCount, nEdges, topIndex, nsmooth, kpp_stage
integer :: edgeCount, nEdges, topIndex, nsmooth, num_levels, kpp_stage
integer, pointer :: nVertLevels, nVertLevelsP1
integer, dimension(:), pointer :: nCellsArray
integer, dimension(:), allocatable :: surfaceAverageIndex

real (kind=RKIND) :: x, bulkRichardsonNumberStop, sfc_layer_depth
real (kind=RKIND) :: normalVelocityAv, delU2, areaSum, blTemp,tangentialVelocityAv
real (kind=RKIND) :: sigma
real (kind=RKIND) :: sigma, columnThickness
real (kind=RKIND), dimension(:), allocatable :: Nsqr_iface, turbulentScalarVelocityScale, &
deltaVelocitySquared, normalVelocitySum, &
potentialDensitySum, RiTemp, &
Expand All @@ -172,7 +173,7 @@ subroutine ocn_vmix_coefs_cvmix_build(meshPool, statePool, forcingPool, err, tim
real (kind=RKIND), dimension(:), allocatable, target :: RiSmoothed, BVFSmoothed, OBLDepths, interfaceForcings
logical :: bulkRichardsonFlag

real (kind=RKIND) :: langmuirEnhancementFactor, alphaAngle
real (kind=RKIND) :: langmuirEnhancementFactor, alphaAngle, vertViscMin

real(kind=RKIND), dimension(:,:), pointer :: stokesDriftZonalWavenumber
real(kind=RKIND), dimension(:,:), pointer :: stokesDriftMeridionalWavenumber
Expand Down Expand Up @@ -320,6 +321,38 @@ subroutine ocn_vmix_coefs_cvmix_build(meshPool, statePool, forcingPool, err, tim
allocate(layerThicknessSum(nVertLevels))
allocate(layerThicknessEdgeSum(nVertLevels))

if (thinFilmViscOn) then
columnThickness = 0.0_RKIND

!$omp parallel
!$omp do schedule(runtime) private(k, num_levels, columnThickness, vertViscMin)
do iCell = 1, nCells
do k = minLevelCell(iCell), maxLevelCell(iCell)
columnThickness = columnThickness + layerThickness(k, iCell)
end do

num_levels = maxLevelCell(iCell) - minLevelCell(iCell) + 1
if (columnThickness < hMin * num_levels) then
if (thinFilmViscOn) then
if (thinFilmRampOn) then
vertViscMin = thinFilmViscConstant * tanh(hRampFactor * &
(columnThickness - hMin * num_levels)/(hMin * num_levels)))
else
vertViscMin = thinFilmViscConstant
endif
endif
do k = 1, nVertLevelsP1
vertViscTopOfCell(k, iCell) = max(vertViscTopOfCell(k, iCell), &
vertViscMin)
end do
end do
end if
columnThickness = 0.0_RKIND
end do
!$omp end do
!$omp end parallel
endif

do k = 1, nVertLevels
Nsqr_iface(k) = 0.0_RKIND
turbulentScalarVelocityScale(k) = 0.0_RKIND
Expand Down Expand Up @@ -1115,6 +1148,18 @@ subroutine ocn_vmix_cvmix_init(domain,err)!{{{
lenhanced_diff = config_cvmix_kpp_use_enhanced_diff)
endif

thinFilmViscOn = config_use_thin_film_viscosity
thinFilmRampOn = config_zero_drying_velocity_ramp
if (thinFilmViscOn) then
thinFilmViscConstant = config_thin_film_viscosity_constant
if (thinFilmRampOn) then
hMin = config_thin_film_viscosity_hmin
hMax = config_thin_film_viscosity_hmax
hRampFactor = config_zero_drying_velocity_ramp_factor
else
hMin = config_drying_min_cell_height
endif
endif

!--------------------------------------------------------------------

Expand Down