.. _inputs_momentum_sources: Section: Momentum Sources ~~~~~~~~~~~~~~~~~~~~~~~~~~ .. input_param:: ICNS.source_terms **type:** String(s), optional Activates source terms for the incompressible Navier-Stokes momentum equations. These strings can be entered in any order with a space between each. Please consult the :doc:`../doxygen/html/index` for a comprehensive list of all momentum source terms available. Note that the following input arguments specific to each source term will only be active if the corresponding source term (the root name) is listed in :input_param:`ICNS.source_terms`. .. input_param:: CoriolisForcing.latitude **type:** Real, mandatory Latitude in degrees where the Coriolis forcing is computed. Positive values indicate northern hemisphere. .. input_param:: CoriolisForcing.rotational_time_period **type:** Real, optional, default = 86400.0 Rotational time period of a day in seconds. .. input_param:: CoriolisForcing.east_vector **type:** List of 3 reals, optional, default = 1.0 0.0 0.0 East vector that gives the orientation of the grid w.r.t. to planetary coordinate system. This vector is automatically normalized within Kynema-SGF. .. input_param:: CoriolisForcing.north_vector **type:** List of 3 reals, optional, default = 0.0 1.0 0.0 North vector that gives the orientation of the grid w.r.t. to planetary coordinate system. This vector is automatically normalized within Kynema-SGF. .. input_param:: GeostrophicForcing.geostrophic_wind **type:** List of 3 reals, optional The user has to choose between GeostrophicForcing and ABLForcing. CoriolisForcing input must be present when using GeostrophicForcing. These checks are not enforced for now. .. input_param:: GeostrophicForcing.geostrophic_wind_timetable **type:** String, optional Input file name for table that lists time in seconds, wind speed in meters per second, and horizontal wind direction in degrees of the Geostrophic forcing velocity. Each line in the file should be a sequence of three floats specifying the inputs in that order (e.g., 0.0 8.0 -5.0). If this argument is present, the :input_param:`GeostrophicForcing.geostrophic_wind` will be ignored. Note that the code expects there to be a single-line header at the beginning of the geostrophic wind timetable file; if no header exists, the first line of data will be ignored. .. input_param:: ABLForcing.abl_forcing_height **type:** Real, mandatory Height in meters at which the flow is forced to maintain the freestream inflow velocities specified through :input_param:`incflo.velocity`. .. input_param:: ABLForcing.velocity_timetable **type:** String, optional Input file name for table that lists time in seconds, wind speed in meters per second, and horizontal wind direction in degrees of the ABL forcing velocity. Each line in the file should be a sequence of three floats specifying the inputs in that order (e.g., 0.0 8.0 -5.0). If this argument is present, the :input_param:`incflo.velocity` argument will be ignored. Note that the code expects there to be a single-line header at the beginning of the velocity timetable file; if no header exists, the first line of data will be ignored. .. input_param:: ABLForcing.forcing_timetable_output_file **type:** String, optional Output file name for writing the ABL forcing vector to a text file over the course of a simulation. This output is primarily intended for replicating the ABL forcing from a precursor simulation in a subsequent inflow-outflow simulation by providing an input file for Body Forcing. The output file will contain the time and three vector components of the force. .. input_param:: ABLForcing.forcing_timetable_frequency **type:** Int, optional The interval of timesteps for writing to the forcing timetable output file. The default is 1, i.e., writing every step, which is also the default of the boundary plane output feature. .. input_param:: ABLForcing.forcing_timetable_start_time **type:** Real, optional The start time for writing to the forcing timetable output file. The default is 0. .. input_param:: ABLForcing.abl_forcing_off_height **type:** Real, required for multiphase simulations with ABL This parameter indicates the vertical distance above the water level that the ABL forcing term should be turned off. This tuning parameter is used to avoid applying the ABL forcing to ocean waves. This is not used when the volume fraction field (vof) is not present in the simulation. .. input_param:: ABLForcing.abl_forcing_ramp_height **type:** Real, required for multiphase simulations with ABL This parameter indicates the vertical distance above the water level and the "off height" that the ABL forcing term should ramp up from zero to full strength. This is not used when the volume fraction field (vof) is not present in the simulation. .. input_param:: ABLForcing.abl_forcing_band **type:** Real, optional for multiphase simulations with ABL This parameter is an additional safeguard against applying ABL forcing within the waves. This specifies the number of computational cells in a band around the air-water interface that the ABL forcing should be deactivated. While the other arguments relate to the height coordinate within the domain, this argument is relative to the actual position of water in the simulation. The default value is 2. .. input_param:: BodyForce.type **type:** String, optional The type of body force being used. The default is uniform_constant, which applies a single constant force vector over the entire domain. Other available types are height_varying, oscillatory, and uniform_constant. .. input_param:: BodyForce.magnitude **type:** List of 3 reals, conditionally mandatory The force vector to be applied as a body force. This argument is mandatory for uniform_constant (default) and oscillatory body force types. .. input_param:: BodyForce.angular_frequency **type:** Real, conditionally mandatory The angular frequency to be used for applying sinusoidal time variation to the body force. This argument is mandatory for the oscillatory body force type and is only active for the oscillatory type. .. input_param:: BodyForce.bodyforce_file **type:** String, conditionally mandatory The text file for specifying the body force vector as a function of height. This text file must contain heights (z coordinate values), force components in x, and force components in y. This argument is mandatory for the height_varying body force type and is only active for the height_varying type. .. input_param:: BodyForce.uniform_timetable_file **type:** String, conditionally mandatory The text file for specifying the body force vector as a function of time. This text file must contain times, force components in x, force components in y, and force components in z. This argument is mandatory for the uniform_timetable body force type and is only active for the uniform_timetable type. Note that the code expects there to be a single-line header at the beginning of the uniform timetable file; if no header exists, the first line of data will be ignored. .. input_param:: DragForcing.drag_coefficient **type:** Real, optional This value specifies the coefficient for the forcing term in the immersed boundary forcing method. It is currently recommended to use the default value to avoid initial numerical stability. .. input_param:: DragForcing.sponge_strength **type:** Real, optional The value of the sponge layer coefficient. It is recommended to use the default value of 1.0. .. input_param:: DragForcing.sponge_density **type:** Real, optional The value of the sponge layer density. It is recommended to use the default value of 1.0. .. input_param:: DragForcing.bc_forcing_time_factor **type:** Real, optional, default = 5.0 This value modifies the time scale of the BC forcing component of DragForcing relative to the time step size. .. input_param:: DragForcing.sponge_west **type:** Boolean, optional, default = false This term turns on the sponge layer in the west (-x) boundary. .. input_param:: DragForcing.sponge_east **type:** Boolean, optional, default = false This term turns on the sponge layer in the east (+x) boundary. .. input_param:: DragForcing.sponge_south **type:** Boolean, optional, default = false This term turns on the sponge layer in the south (-y) boundary. .. input_param:: DragForcing.sponge_north **type:** Boolean, optional, default = false This term turns on the sponge layer in the north (+y) boundary. .. input_param:: DragForcing.sponge_distance_west **type:** Real, mandatory if west sponge is active This value is specified as a negative value when the inflow x-velocity is <=0. .. input_param:: DragForcing.sponge_distance_east **type:** Real, mandatory if east sponge is active This value is specified as a positive value when the inflow x-velocity is >=0. .. input_param:: DragForcing.sponge_distance_south **type:** Real, mandatory if south sponge is active This value is specified as a negative value when the inflow y-velocity is <=0. .. input_param:: DragForcing.sponge_distance_north **type:** Real, mandatory if north sponge is active This value is specified as a positive value when the inflow y-velocity is >=0. .. input_param:: DragForcing.is_laminar **type:** int, optional This term turns off the sponge layer. This term is required for terrain simulations with periodic boundary conditions. The default value is 0. .. input_param:: DragForcing.wave_model_inviscid_form_drag **type:** Boolean, optional, default = false This input file option turns on or off an inviscid model for the form drag of waves in the domain. The formulation of this model is adapted from the Moving Surface Drag (MOSD) model developed by `Ayala et al (2024) `_. When the OceanWaves physics module is active, and the volume fraction variable ("vof") is not in the simulation, DragForcing will represent ocean waves as moving terrain. This is automatic and independent of DragForcing input arguments. When waves are represented as moving terrain and there is sufficient mesh resolution to resolve the shape of the wave, the blanking of cells performed by the DragForcing routine will naturally introduce the form drag of the waves into the flow. However, when the waves are not sufficiently resolved, such as when the wave amplitude is less than the cell height, the analytical model for the form drag, activated by setting this option to true, can be used to compensate for the lack of resolution. Therefore, this option should remain set to false except in scenarios when the form drag is known to be under-resolved. The following arguments are influential when ``GravityForcing`` is included in :input_param:`ICNS.source_terms`. .. input_param:: ICNS.use_perturb_pressure **type:** Boolean, optional, default = false When this option is off, the GravityForcing term is simply :math:`g`, which becomes :math:`\rho g` when included in the momentum equation. By activating this option, the momentum term applied by GravityForcing will become :math:`(\rho - \rho_0) g`, where :math:`rho_0` is some constant reference density profile. The reference density field can be created by either MultiPhase physics or anelastic ABL physics. By using the reference density, the pressure field seen by the solver is represented as a perturbation from a reference pressure field, enabling pressure_outflow boundary conditions to better handle certain flows, e.g., those with equilibrium pressure gradients parallel to the outflow plane. .. input_param:: ICNS.reconstruct_true_pressure **type:** Boolean, optional, default = false This option is only valid when the perturbational pressure form is being used, i.e., :input_param:`ICNS.use_perturb_pressure` = true. Reconstructing the true pressure adds back the reference pressure profile to obtain the full pressure after the pressure solve has been performed. This makes no difference to the flow evolution, but it changes the field available for post-processing or coupling to overset solvers.