mom_set_visc mom_set_visc::set_visc_cs subroutine, public subroutine, public mom_set_visc::set_viscous_bbl (u, v, h, tv, visc, G, GV, US, CS, symmetrize) set_viscous_bbl u u v v h h tv tv visc visc G G GV GV US US CS CS symmetrize symmetrize Calculates the thickness of the bottom boundary layer and the viscosity within that layer. A drag law is used, either linearized about an assumed bottom velocity or using the actual near-bottom velocities combined with an assumed unresolved velocity. The bottom boundary layer thickness is limited by a combination of stratification and rotation, as in the paper of Killworth and Edwards, JPO 1999. It is not necessary to calculate the thickness and viscosity every time step; instead previous values may be used. If set_visc_cs.bottomdraglaw is True then a bottom boundary layer viscosity and thickness are calculated so that the bottom stress is \[ \mathbf{\tau}_b = C_d | U_{bbl} | \mathbf{u}_{bbl} \] If set_visc_cs.bottomdraglaw is True then the term $|U_{bbl}|$ is set equal to the value in set_visc_cs.drag_bg_vel so that $C_d |U_{bbl}|$ becomes a Rayleigh bottom drag. Otherwise $|U_{bbl}|$ is found by averaging the flow over the bottom set_visc_cs.hbbl of the model, adding the amplitude of tides set_visc_cs.tideamp and a constant set_visc_cs.drag_bg_vel. For these calculations the vertical grid at the velocity component locations is found by \[ \begin{array}{ll} \frac{2 h^- h^+}{h^- + h^+} & u \left( h^+ - h^-\right) >= 0 \\ \frac{1}{2} \left( h^- + h^+ \right) & u \left( h^+ - h^-\right) < 0 \end{array} \] which biases towards the thin cell if the thin cell is upwind. Biasing the grid toward thin upwind cells helps increase the effect of viscosity and inhibits flow out of these thin cells.After diagnosing $|U_{bbl}|$ over a fixed depth an active viscous boundary layer thickness is found using the ideas of Killworth and Edwards, 1999 (hereafter KW99). KW99 solve the equation \[ \left( \frac{h_{bbl}}{h_f} \right)^2 + \frac{h_{bbl}}{h_N} = 1 \] for the boundary layer depth $h_{bbl}$. Here \[ h_f = \frac{C_n u_*}{f} \] is the rotation controlled boundary layer depth in the absence of stratification. $u_*$ is the surface friction speed given by \[ u_*^2 = C_d |U_{bbl}|^2 \] and is a function of near bottom model flow. \[ h_N = \frac{C_i u_*}{N} = \frac{ (C_i u_* )^2 }{g^\prime} \] is the stratification controlled boundary layer depth. The non-dimensional parameters $C_n=0.5$ and $C_i=20$ are suggested by Zilitinkevich and Mironov, 1996.If a Richardson number dependent mixing scheme is being used, as indicated by set_visc_cs.rino_mix, then the boundary layer thickness is bounded to be no larger than a half of set_visc_cs.hbbl .TodoChannel drag needs to be explainedA BBL viscosity is calculated so that the no-slip boundary condition in the vertical viscosity solver implies the stress $\mathbf{\tau}_b$. Killworth, P. D., and N. R. Edwards, 1999: A Turbulent Bottom Boundary Layer Code for Use in Numerical Ocean Models. J. Phys. Oceanogr., 29, 1221-1238, doi:10.1175/1520-0485(1999)029<1221:ATBBLC>2.0.CO;2 Zilitinkevich, S., Mironov, D.V., 1996: A multi-limit formulation for the equilibrium depth of a stably stratified boundary layer. Boundary-Layer Meteorology 81, 325-351. doi:10.1007/BF02430334 g The ocean's grid structure. gv The ocean's vertical grid structure. us A dimensional unit scaling type u The zonal velocity [L T-1 ~> m s-1]. v The meridional velocity [L T-1 ~> m s-1]. h Layer thicknesses [H ~> m or kg m-2]. tv A structure containing pointers to any available thermodynamic fields. Absent fields have NULL ptrs.. visc A structure containing vertical viscosities and related fields. cs The control structure returned by a previous call to set_visc_init. symmetrize If present and true, do extra calculations of those values in visc that would be calculated with symmetric memory. mom_error_handler::mom_error set_u_at_v set_v_at_u real function real function mom_set_visc::set_v_at_u (v, h, G, i, j, k, mask2dCv, OBC) set_v_at_u v v h h G G i i j j k k mask2dCv mask2dCv OBC OBC This subroutine finds a thickness-weighted value of v at the u-points. g The ocean's grid structure v The meridional velocity [L T-1 ~> m s-1] h Layer thicknesses [H ~> m or kg m-2] i The i-index of the u-location to work on. j The j-index of the u-location to work on. k The k-index of the u-location to work on. mask2dcv A multiplicative mask of the v-points obc A pointer to an open boundary condition structure The return value of v at u points points in the same units as u, i.e. [L T-1 ~> m s-1] or other units. set_viscous_bbl set_viscous_ml real function real function mom_set_visc::set_u_at_v (u, h, G, i, j, k, mask2dCu, OBC) set_u_at_v u u h h G G i i j j k k mask2dCu mask2dCu OBC OBC This subroutine finds a thickness-weighted value of u at the v-points. g The ocean's grid structure u The zonal velocity [L T-1 ~> m s-1] or other units. h Layer thicknesses [H ~> m or kg m-2] i The i-index of the u-location to work on. j The j-index of the u-location to work on. k The k-index of the u-location to work on. mask2dcu A multiplicative mask of the u-points obc A pointer to an open boundary condition structure The return value of u at v points in the same units as u, i.e. [L T-1 ~> m s-1] or other units. set_viscous_bbl set_viscous_ml subroutine, public subroutine, public mom_set_visc::set_viscous_ml (u, v, h, tv, forces, visc, dt, G, GV, US, CS, symmetrize) set_viscous_ml u u v v h h tv tv forces forces visc visc dt dt G G GV GV US US CS CS symmetrize symmetrize Calculates the thickness of the surface boundary layer for applying an elevated viscosity. A bulk Richardson criterion or the thickness of the topmost NKML layers (with a bulk mixed layer) are currently used. The thicknesses are given in terms of fractional layers, so that this thickness will move as the thickness of the topmost layers change. g The ocean's grid structure. gv The ocean's vertical grid structure. us A dimensional unit scaling type u The zonal velocity [L T-1 ~> m s-1]. v The meridional velocity [L T-1 ~> m s-1]. h Layer thicknesses [H ~> m or kg m-2]. tv A structure containing pointers to any available thermodynamic fields. Absent fields have NULL ptrs. forces A structure with the driving mechanical forces visc A structure containing vertical viscosities and related fields. dt Time increment [T ~> s]. cs The control structure returned by a previous call to set_visc_init. symmetrize If present and true, do extra calculations of those values in visc that would be calculated with symmetric memory. mom_error_handler::mom_error set_u_at_v set_v_at_u mom_dynamics_split_rk2::step_mom_dyn_split_rk2 mom_dynamics_unsplit::step_mom_dyn_unsplit mom_dynamics_unsplit_rk2::step_mom_dyn_unsplit_rk2 subroutine, public subroutine, public mom_set_visc::set_visc_register_restarts (HI, GV, param_file, visc, restart_CS) set_visc_register_restarts HI HI GV GV param_file param_file visc visc restart_CS restart_CS Register any fields associated with the vertvisc_type. hi A horizontal index type structure. gv The ocean's vertical grid structure. param_file A structure to parse for run-time parameters. visc A structure containing vertical viscosities and related fields. Allocated here. restart_cs A pointer to the restart control structure. mom_cvmix_conv::cvmix_conv_is_used mom_cvmix_shear::cvmix_shear_is_used mom_kappa_shear::kappa_shear_at_vertex mom_kappa_shear::kappa_shear_is_used subroutine, public subroutine, public mom_set_visc::set_visc_init (Time, G, GV, US, param_file, diag, visc, CS, restart_CS, OBC) set_visc_init Time Time G G GV GV US US param_file param_file diag diag visc visc CS CS restart_CS restart_CS OBC OBC Initializes the MOM_set_visc control structure. time The current model time. g The ocean's grid structure. gv The ocean's vertical grid structure. us A dimensional unit scaling type param_file A structure to parse for run-time parameters. diag A structure that is used to regulate diagnostic output. visc A structure containing vertical viscosities and related fields. Allocated here. cs A pointer that is set to point to the control structure for this module restart_cs A pointer to the restart control structure. obc A pointer to an open boundary condition structure mom_kappa_shear::kappa_shear_at_vertex mom_kappa_shear::kappa_shear_is_used mom_error_handler::mom_error mom_restart::register_restart_field_as_obsolete subroutine, public subroutine, public mom_set_visc::set_visc_end (visc, CS) set_visc_end visc visc CS CS This subroutine dellocates any memory in the set_visc control structure. visc A structure containing vertical viscosities and related fields. Elements are deallocated here. cs The control structure returned by a previous call to set_visc_init. Calculates various values related to the bottom boundary layer, such as the viscosity and thickness of the BBL (set_viscous_BBL). This would also be the module in which other viscous quantities that are flow-independent might be set. This information is transmitted to other modules via a vertvisc type structure.The same code is used for the two velocity components, by indirectly referencing the velocities and defining a handful of direction-specific defined variables.