Section: Actuator

This section controls the actuator type models. This includes the actuator disk and line models. The prefix is the label set in incflo.physics. For example incflo.physics = FreeStream Actuator Actuator models are meant to simulate aerodynamic objects by using body forces in the momentum equation. There are capabilities to simulate fixed wings as actuator lines and wind turbines as actuator disks and actuator line models.

Actuator.labels

type: String, mandatory

This string is used as an identifier for the current actuator.

Actuator.type

type: String, mandatory

This string identifies the type of actuator to use. The ones currently supported are: UniformCtDisk, JoukowskyDisk, TurbineFastLine, TurbineFastDisk, TurbineKynemaLine, TurbineKynemaFMBLine, TurbineKynemaFMBDisk, FixedWingLine, and ActuatorSector.

The Kynema-FMB coupled actuator turbine types are documented in the dedicated reference page Actuator-Based Kynema-FMB Coupling.

It is recommended to group common parameters across actuators using the Actuator.[type].[param]. For example:

Actuator.Turb1.type            = UniformCtDisk"
Actuator.Turb1.epsilon         = 5.0 5.0 5.0"
Actuator.Turb2.type            = UniformCtDisk"
Actuator.Turb2.epsilon         = 5.0 5.0 5.0"

becomes:

Actuator.UniformCtDisk.epsilon = 5.0 5.0 5.0"
Actuator.Turb1.type            = UniformCtDisk"
Actuator.Turb2.type            = UniformCtDisk"

FixedWingLine

Example for FixedWingLine:

incflo.physics = FreeStream Actuator
Actuator.labels = F1
Actuator.type = FixedWingLine
Actuator.FixedWingLine.num_points = 21
Actuator.FixedWingLine.epsilon = 3.0 3.0 3.0
Actuator.FixedWingLine.epsilon_chord = 0.25 0.25 0.25
Actuator.FixedWingLine.fllc = 0
Actuator.FixedWingLine.pitch = 4.0
Actuator.FixedWingLine.span_locs = 0.0 1.0
Actuator.FixedWingLine.chord = 2.0 2.0
Actuator.FixedWingLine.airfoil_table = DU21_A17.txt
Actuator.FixedWingLine.airfoil_type = openfast
Actuator.F1.start = 0.0 -4.0 0.0
Actuator.F1.end = 0.0 4.0 0.0
Actuator.F1.output_frequency = 10
ICNS.source_terms = ActuatorForcing

Actuator.FixedWingLine.num_points

type: int, mandatory

This is the number of actuator points along the wing to be used in the simulation.

Actuator.FixedWingLine.epsilon

type: List of 3 real numbers, mandatory

This is the value of epsilon in the chord, thickness and spanwise directions.

Actuator.FixedWingLine.epsilon_chord

type: List of 3 real numbers, optional

This is the value of epsilon/chord. This value will be used to compute epsilon as a function of the chord at every actuator point. A value of epsilon / chord ~ 0.25 is recommended for an optimal representation of the blade aerodynamics. When this variable is specified, the code will choose the maximum value between epsilon_chord * chord and epsilon for every actuator point.

Actuator.FixedWingLine.fllc

type: Bool, optional

This option will activate the filtered lifting line correction (fllc). The correction follows the implementation of Martinez-Tossas and Meneveau (2019) and Blaylock et al (2022). The use of the fllc requires epsilon and an optimal epsilon_chord as an input. The recommended value is 0.25 in all directions for epsilon_chord and a value of epsilon in all directions that would be greater than at least 2.5 times the grid size dx. The default is 0.

Actuator.FixedWingLine.fllc_type

type: String, optional, default = variable_chord

This option tells whether to use the original fllc formulation outlined in Martinez-Tossas and Meneveau (2019), which assumes a constant chord length across blade (specified as constant_chord), or to use a new formulation outlined in Martinez-Tossas et al. (2023), which accounts for chord variations (specified as variable_chord).

Actuator.FixedWingLine.fllc_relaxation_factor

type: Double, optional

The relaxation factor to be applied to the updated velocity see: Martinez-Tossas and Meneveau (2019) The default value is 0.1.

Actuator.FixedWingLine.fllc_start_time

type: Double, optional

The time in the simulation from when to start using the correction. The default value is 0.

Actuator.FixedWingLine.fllc_nonuniform

type: Bool

The flag to specify if the actuator points used to compute the correction should be non-uniformly distributed. This helps in using less points for the fllc while still maintaining the accuracy of the fllc. The default value is true.

Actuator.FixedWingLine.fllc_epsilon_dr_ratio

type: Double, optional

The ratio of epsilon to actuator point spacing used to create a non-uniform distribution. A value of 1 or greater is recommended. The default value is 1.

Actuator.FixedWingLine.pitch

type: Real number, mandatory

This is the pitch angle of the blade in degrees. All coordinates will be pitched by this angle. In the case of a fixed wing, this would be the angle of attack of the wing with respect to the inflow velocity. This argument is mandatory unless a pitch timetable is specified.

Actuator.FixedWingLine.span_locs

type: List of real numbers, mandatory

These are non-dimensional span locations from 0 to 1. These locations are used to specify the chord values at every span location of the blade.

Actuator.FixedWingLine.chord

type: List of real numbers, mandatory

These are the chord values at every span location. The length of this array needs to be the same length as span_locs.

Actuator.FixedWingLine.airfoil_table

type: String, mandatory

This is the name of the file that contains the lookup table for lift and drag coefficients.

Actuator.FixedWingLine.airfoil_type

type: String, mandatory

This is the type of airfoil table lookup. The currently supported options are openfast and text.

Actuator.F1.start

type: List of 3 real numbers, mandatory

This is the starting point of the wing where the first actuator point will be.

Actuator.F1.end

type: List of 3 real numbers, mandatory

This is the end point of the wing where the last actuator point will be.

Actuator.F1.output_frequency

type: int, optional

This is how often to write actuator output. The default is 10.

Actuator.FixedWingLine.motion_type

type: String, optional

The FixedWingLine actuator allows for motion, though other aspects of the actuator remain fixed (such as the orientation and the dimensions). The currently supported options are none (default), linear, and sine. Linear motion moves the actuator at a constant velocity in a straight line whereas sine motion oscillates the actuator according to a temporal sine signal.

Actuator.FixedWingLine.velocity

type: List of 3 real numbers, mandatory when motion_type = linear

This vector provides the prescribed constant velocity of the actuator motion.

Actuator.FixedWingLine.sine_vector

type: List of 3 real numbers, mandatory when motion_type = sine

This vector provides the actuator displacement from its initial, specified location as it moves according to the oscillatory sine signal. The range of motion of the actuator will be between (initial location + sine vector) and (initial location - sine vector).

Actuator.FixedWingLine.sine_period

type: Real number, mandatory when motion_type = linear

This value specifies the temporal period of the sine signal.

Actuator.FixedWingLine.pitch_timetable

type: String, optional

File name of pitch timetable. This file must specify pitch angles at different times below a one-line header. When this argument is present, the pitch argument is no longer mandatory, and it will not be used.

Actuator.FixedWingLine.disable_spanwise_gaussian

type: Boolean, optional, default = false

When this option is turned on, the actuator Gaussian is disabled in the spanwise Gaussian, making the force distribution uniform in that direction. This option enables quasi-2D simulations with a fixed wing. The code will print warning statements if the detected spanwise direction is not periodic.

Actuator.FixedWingLine.normalize_spanwise

type: Boolean, optional, default = true

When the disable_spanwise_gaussian is true, the default behavior is to normalize the Gaussian and force quantities in the spanwise direction, preventing the number of actuator points or the actuator point spacing from affecting the results. When this option is false, the ordinary treatment of the Gaussian and force quantities in the spanwise direction is used instead. Setting this option to false can be useful for verification studies.

Actuator.FixedWingLine.prescribed_uinf

type: Real, optional, default = -1.0

This input allows the freestream velocity sampled by the actuator routines to be overwritten with a user-prescribed value. This feature becomes active when the prescribed value is non-negative.

Actuator.FixedWingLine.active_force_dirs

type: List of 3 real numbers, optional, default = 1.0 1.0 1.0

By default, the actuator force is computed and applied in every coordinate direction. This input allows actuator force coordinate directions to be deactivated by specifying a 0.0 in for the x, y, or z component of this vector.

ActuatorSector

The ActuatorSector model represents rotating blades by computing blade loads at the midpoint blade locations and sweeping those loads through the time step during Gaussian projection. If the time step is small enough, the adaptive swept quadrature uses one point per radial station and the model naturally reduces to an actuator-line-like projection.

Example for ActuatorSector:

incflo.physics = FreeStream Actuator
ICNS.source_terms = ActuatorForcing
Actuator.labels = R1
Actuator.type = ActuatorSector
Actuator.ActuatorSector.rotor_diameter = 0.10
Actuator.ActuatorSector.root_radius_fraction = 0.18
Actuator.ActuatorSector.num_blades = 2
Actuator.ActuatorSector.omega = 2500.0
Actuator.ActuatorSector.center = 0.0 0.0 0.0
Actuator.ActuatorSector.translation_velocity = 0.0 0.0 0.0
Actuator.ActuatorSector.rotor_normal = 1.0 0.0 0.0
Actuator.ActuatorSector.rotor_rotation_degrees_per_revolution = 0.0 2.0 0.0
Actuator.ActuatorSector.epsilon_chord = 0.5
Actuator.ActuatorSector.epsilon_dr = 1.5
Actuator.ActuatorSector.epsilon_dl = 1.5
Actuator.ActuatorSector.min_chord_dr = 2.0
Actuator.ActuatorSector.span_locs = 0.0 1.0
Actuator.ActuatorSector.chord = 0.01 0.006
Actuator.ActuatorSector.twist = 12.0 4.0
Actuator.ActuatorSector.airfoil_table = airfoil.txt
Actuator.ActuatorSector.airfoil_type = openfast
Actuator.ActuatorSector.gaussian_type = table
Actuator.ActuatorSector.gaussian_table_error = 1.0e-4
Actuator.ActuatorSector.output_frequency = 1

Actuator.ActuatorSector.rotor_diameter

type: Real number, mandatory

Rotor diameter in meters.

Actuator.ActuatorSector.root_radius_fraction

type: Real number, optional, default = 0.18

Inboard cutoff radius divided by rotor radius. The generated radial grid covers root_radius_fraction * rotor_radius <= r <= rotor_radius.

Actuator.ActuatorSector.num_blades

type: int, optional, default = 2

Number of rotor blades.

Actuator.ActuatorSector.omega

type: Real number, mandatory

Rotor angular speed in rad/s. Positive values follow the clockwise-positive blade convention used by the actuator-sector theory.

Actuator.ActuatorSector.center

type: List of 3 real numbers, optional, default = 0.0 0.0 0.0

Initial rotor hub center in meters in the CFD frame.

Actuator.ActuatorSector.translation_velocity

type: List of 3 real numbers, optional, default = 0.0 0.0 0.0

Prescribed drone/body translational velocity in m/s in the CFD frame.

Actuator.ActuatorSector.rotor_normal

type: List of 3 real numbers, optional, default = 1.0 0.0 0.0

Initial rotor-axis normal direction in the fixed frame. The vector is normalized internally and must be nonzero. The default places the rotor disk in the fixed-frame y-z plane, with the rotor normal pointing along +x.

Actuator.ActuatorSector.rotor_rotation_degrees_per_revolution

type: List of 3 real numbers, optional, default = 0.0 0.0 0.0

Prescribed rotor-frame/body rotation rate in fixed-frame XYZ degrees per blade revolution. This is converted to rotor_angular_velocity internally using omega. For example, the vector 0.0 2.0 0.0 rotates the rotor normal about fixed-frame y by two degrees per blade revolution.

Actuator.ActuatorSector.rotor_angular_velocity

type: List of 3 real numbers, optional

Rotor-frame/body angular velocity in rad/s in the CFD frame. If specified, this overrides rotor_rotation_degrees_per_revolution.

Actuator.ActuatorSector.epsilon

type: Real number, optional

Fixed Gaussian width in meters. At least one of epsilon or epsilon_chord must be specified. When epsilon is specified, the same constant width is used at every radial station. If both epsilon and epsilon_chord are specified, epsilon takes precedence and a warning is printed.

Actuator.ActuatorSector.epsilon_chord

type: Real number, optional

Gaussian width divided by local chord. At least one of epsilon or epsilon_chord must be specified. When epsilon_chord is used, the local Gaussian width is max(epsilon_min, epsilon_chord * chord).

Actuator.ActuatorSector.epsilon_min

type: Real number, optional, default = 0.0

Minimum Gaussian width in meters when using epsilon_chord. This value is ignored when constant epsilon is specified.

Actuator.ActuatorSector.epsilon_dr

type: Real number, optional, default = 1.5

Radial grid requirement. The radial grid is built automatically so that epsilon / dr >= epsilon_dr. Users do not specify the number of radial stations directly; it is derived from the local smoothing width, chord, and rotor radius.

Actuator.ActuatorSector.epsilon_dl

type: Real number, optional, default = 1.5

Swept arc length requirement. Swept quadrature is selected automatically so that epsilon / dl >= epsilon_dl over the rotor sweep in the current timestep. When the timestep is sufficiently small, each radial station uses one swept point and the projection reduces to an actuator-line-like limit.

Note

The actuator-sector model is intended to permit larger timesteps than a conventional actuator-line representation of a rotating blade. The swept forcing sector is set by the CFD timestep, delta_theta = omega * dt, so increasing dt increases the azimuthal sector covered during each force update.

In practice, the timestep is still limited by the CFD stability constraint. Users may often run sector-model cases with a larger CFL number than an actuator-line case, but the final timestep will depend on the mesh spacing, resolved and induced velocities, solver settings, and boundary conditions. If the CFD timestep becomes small, for example after grid refinement, the swept sector narrows and the model naturally approaches the actuator-line limit.

Actuator.ActuatorSector.min_chord_dr

type: Real number, optional, default = 2.0

Additional radial grid requirement. The radial grid also satisfies chord / dr >= min_chord_dr.

Actuator.ActuatorSector.span_locs

type: List of real numbers, optional, default = 0.0 1.0

Non-dimensional radial locations for chord and twist interpolation.

Actuator.ActuatorSector.chord

type: List of real numbers, optional, default = 1.0 1.0

Chord distribution in meters at span_locs.

Actuator.ActuatorSector.twist

type: List of real numbers, optional, default = 0.0 0.0

Twist distribution in degrees at span_locs.

Actuator.ActuatorSector.airfoil_table

type: String, mandatory

Airfoil lookup table. The same loader as FixedWingLine is used.

Actuator.ActuatorSector.airfoil_type

type: String, optional, default = openfast

Airfoil lookup table format. The currently supported options are the same as for FixedWingLine.

Actuator.ActuatorSector.support_radius_over_epsilon

type: Real number, optional, default = 3.0

Compact Gaussian support radius divided by the local Gaussian width. Force contributions are ignored outside this radius.

Actuator.ActuatorSector.radial_quadrature

type: String, optional, default = midpoint

Radial quadrature rule used to place blade-section force points. The current implementation supports midpoint.

Actuator.ActuatorSector.swept_quadrature

type: String, optional, default = midpoint

Swept-sector quadrature rule used to distribute the blade-section force through the timestep. The current implementation supports midpoint.

Actuator.ActuatorSector.gaussian_type

type: String, optional, default = direct

Gaussian evaluation mode. Valid options are direct and table. The table mode interpolates the normalized exp(-r^2) kernel.

Actuator.ActuatorSector.gaussian_table_error

type: Real number, optional, default = 1.0e-4

Maximum absolute interpolation error for the tabulated exp(-x) Gaussian kernel, where x = (r / epsilon)^2. The code derives the number of table intervals from the linear interpolation error bound over 0 <= x <= support_radius_over_epsilon^2.

Actuator.ActuatorSector.output_frequency

type: int, optional, default = 1

Blade-load NetCDF output interval in timesteps. The output is written under post_processing/actuatorXXXXX/<label>.nc and includes the blade radial grid, section loads, integrated thrust and torque, local relative velocity components vel_rel_theta and vel_rel_normal, angle of attack, and airfoil coefficients.

TurbineFastLine

This actuator type requires an Kynema-SGF build with OpenFAST coupling enabled. Kynema-SGF provides flow quantities at the actuator point locations to OpenFAST and OpenFAST provides the actuator point locations and forces at those points. This tight coupling happens at every time step.

Example for TurbineFastLine:

incflo.physics = FreeStream Actuator
Actuator.labels = WTG01
Actuator.type = TurbineFastLine
Actuator.TurbineFastLine.rotor_diameter = 126.0
Actuator.TurbineFastLine.hub_height = 90.0
Actuator.TurbineFastLine.num_points_blade = 64
Actuator.TurbineFastLine.num_points_tower = 12
Actuator.TurbineFastLine.epsilon = 10.0 10.0 10.0
Actuator.TurbineFastLine.epsilon_chord = 0.25 0.25 0.25
Actuator.TurbineFastLine.fllc = 0
Actuator.TurbineFastLine.epsilon_tower = 5.0 5.0 5.0
Actuator.TurbineFastLine.openfast_start_time = 0.0
Actuator.TurbineFastLine.openfast_stop_time = 1.0
Actuator.TurbineFastLine.nacelle_drag_coeff = 0.0
Actuator.TurbineFastLine.nacelle_area = 0.0
Actuator.TurbineFastLine.output_frequency = 10
Actuator.TurbineFastLine.density = 1.225
Actuator.WTG01.base_position = 5.0191 0. -89.56256
Actuator.WTG01.openfast_input_file = "fast_inp/nrel5mw.fst"
ICNS.source_terms = ActuatorForcing

Actuator.TurbineFastLine.rotor_diameter

type: Real number, required

This is the rotor diameter of the turbine to be simulated.

Actuator.TurbineFastLine.hub_height

type: Real number, required

This is the hub height of the turbine.

Actuator.TurbineFastLine.num_points_blade

type: int, required

This the number of actuator points along the blades.

Actuator.TurbineFastLine.num_points_tower

type: int, required

This is the number of actuator points along the tower.

Actuator.TurbineFastLine.epsilon: Same as Actuator.FixedWingLine.epsilon.

Actuator.TurbineFastLine.epsilon_chord: Same as Actuator.FixedWingLine.epsilon_chord.

Actuator.TurbineFastLine.fllc: Same as Actuator.FixedWingLine.fllc.

Actuator.TurbineFastLine.fllc_relaxation_factor: Same as Actuator.FixedWingLine.fllc_relaxation_factor.

Actuator.TurbineFastLine.fllc_type: Same as Actuator.FixedWingLine.fllc_type.

Actuator.TurbineFastLine.openfast_start_time

type: Real, required

This is the time at which to start the openfast simulation.

Actuator.TurbineFastLine.openfast_stop_time

type: Real, required

This is the time at which to stop the openfast run.

Actuator.TurbineFastLine.nacelle_drag_coeff

type: Real, optional

This is the drag coefficient of the nacelle. If this and the area of the nacelle are specified, a value of epsilon for the nacelle is computed that would provide an optimal momentum thickness of the wake. This is also used to correct the sampled velocity at the location of the nacelle actuator point.

Actuator.TurbineFastLine.nacelle_area

type: Real, optional, default=0

This is the frontal area of the nacelle which is used to compute the force.

Actuator.TurbineFastLine.output_frequency

type: int, optional, default=10

This is how often to write actuator output.

Actuator.TurbineFastLine.density

type: Real, optional

This is the density of the fluid specified in openfast. This is used to non-dimensionalize the forces from openfast.

Actuator.WTG01.openfast_input_file

type: String, required

This is the name of the openfast input file with all the turbine information.

TurbineKynemaLine

This actuator type requires an Kynema-SGF build with Kynema coupling enabled. This is a similar coupling to OpenFAST, but Kynema acts as the turbine solver in this instance. Some turbine quantities that the OpenFAST interface needs from the Kynema-SGF input file are instead found directly by the code within the Kynema input file, whereas other quantities that OpenFAST has stored within its inputs need to be directly supplied through the Kynema-SGF input file for Kynema, especially for initialization.

Example for TurbineKynemaLine:

incflo.physics = FreeStream Actuator
Actuator.labels = WTG01
Actuator.type = TurbineKynemaLine
## Turbine discretization parameters
Actuator.TurbineKynemaLine.num_struct_nodes_blade = 6
Actuator.TurbineKynemaLine.num_struct_nodes_tower = 6
Actuator.TurbineKynemaLine.num_points_blade = 64
Actuator.TurbineKynemaLine.num_points_tower = 7
## Turbine setup
Actuator.TurbineKynemaLine.rot_speed_rpm    = 12.1
Actuator.TurbineKynemaLine.yaw_deg = 30
Actuator.WTG01.kynema_input_file = NREL-15MW-aero.yaml
Actuator.WTG01.base_position = 5.0191 0. -89.56256
## Turbine - flow coupling parameters
Actuator.TurbineKynemaLine.epsilon = 10.0 10.0 10.0
Actuator.TurbineKynemaLine.epsilon_chord = 0.25 0.25 0.25
Actuator.TurbineKynemaLine.fllc = 0
Actuator.TurbineKynemaLine.nacelle_drag_coeff = 0.0
Actuator.TurbineKynemaLine.nacelle_area = 0.0
Actuator.TurbineKynemaLine.density = 1.225
## Turbine controller parameters and initial state
Actuator.TurbineKynemaLine.controller_shared_library_path = /path/to/libdiscon.so # or libdiscon.dylib
Actuator.TurbineKynemaLine.generator_power_init = 5e6
Actuator.TurbineKynemaLine.hub_wind_vector_init = 9.8726896031426 5.7 0.0
Actuator.TurbineKynemaLine.generator_efficiency = 0.944
## Turbine solver numerical parameters
Actuator.TurbineKynemaLine.dt = 0.01
Kynema.abs_err_tol = 1e-6

Actuator.TurbineKynemaLine.output_frequency = 10

ICNS.source_terms = ActuatorForcing

Actuator.TurbineKynemaLine.num_struct_nodes_blade

type: Int, required

This is the number of structural nodes for Kynema to use when modeling each turbine blade.

Actuator.TurbineKynemaLine.num_struct_nodes_tower

type: Int, required

This is the number of structural nodes for Kynema to use when modeling the turbine tower.

Actuator.TurbineKynemaLine.num_points_blade

type: Int, required

This is the number of aerodynamic sections for Kynema to use when modeling each turbine blade. This will correspond to the number of force points and velocity points on each blade in Kynema-SGF. This must be the same number as provided in the Kynema input file.

Actuator.TurbineKynemaLine.num_points_tower

type: Int, required

This is the number of aerodynamic sections for Kynema to use when modeling the tower. Setting this value to zero will disable aerodynamic representation of the tower and any forces from the tower. If nonzero, this must be the same number of points as provided in the Kynema input file under the tower outer shape.

Actuator.TurbineKynemaLine.rot_speed_rpm

type: Real, optional, default = 0

This is the initial rotational speed of the turbine in RPM. This parameter can alternatively be set in radians per second using the input parameter Actuator.TurbineKynemaLine.rot_speed_radps.

Actuator.TurbineKynemaLine.rot_speed_radps

type: Real, optional, default = 0

This is the initial rotational speed of the turbine in radians per second. If this argument is present, Actuator.TurbineKynemaLine.rot_speed_rpm will be ignored.

Actuator.TurbineKynemaLine.yaw_deg

type: Real, optional, default = 0

This is the initial yaw angle of the turbine in degrees, counterclockwise from the -x direction. This parameter can alternatively be set in radians using the input parameter Actuator.TurbineKynemaLine.yaw_rad.

Actuator.TurbineKynemaLine.yaw_rad

type: Real, optional, default = 0

This is the initial yaw angle of the turbine in radians. If this argument is present, Actuator.TurbineKynemaLine.yaw_deg will be ignored.

Actuator.TurbineKynemaLine.kynema_input_file

type: String, required

This is the input file used to initialize the Kynema turbine model. It conforms to the WindIO format. A pre-processing tool is provided in the Kynema repository to change the number of aerodynamic sections per blade, if needed, as well as to address some format edge cases.

Actuator.TurbineKynemaLine.controller_shared_library_path

type: String, optional, default = empty

This is the path to the controller shared library (typically ROSCO). If this parameter is not provided, no controller will be created in the turbine model, and the controller-related input parameters will not be used.

Actuator.TurbineKynemaLine.generator_power_init

type: Real, optional, default = 0

Power of the generator at the start of the simulation.

Actuator.TurbineKynemaLine.hub_wind_vector_init

type: Vector<Real>, optional, default = 0 0 0

This is the initial wind vector that the turbine hub is exposed to. It does not have to be the actual wind there at initialization; this number is converted to a wind speed that is used as the controller’s initial guess.

Actuator.TurbineKynemaLine.generator_efficiency

type: Real, optional, default = 1

This is the efficiency of the generator. If not populated, the efficiency is assumed to be 1, i.e., 100%.

Actuator.TurbineKynemaLine.dt

type: Real, optional, default = same as Kynema-SGF dt

This is the time step size chosen for the Kynema turbine model. It must be a factor of the Kynema-SGF time step so that Kynema can take an integer number of sub-steps for each Kynema-SGF time step. If not populated, the Kynema time step size will be the same as the flow solver time step, and, due to the robustness of Kynema, this is typically fine.

Actuator.TurbineKynemaLine.output_frequency

type: Int, optional, default = 10

This is how often, in time steps, to output actuator data from Kynema-SGF. Note, this does not govern how often Kynema outputs turbine data. Kynema automatically outputs data every Kynema-SGF time step.

Kynema.abs_err_tol

type: Real, optional, default = 1e-5

This turbine solver parameter is not turbine-specific; rather, it informs the solution parameters of Kynema overall. This, in particular, sets the absolute tolerance of the Kynema solver.

Kynema.rel_err_tol

type: Real, optional, default = 1e-4

This parameter sets the relative tolerance of the Kynema solver.

Kynema.max_nonlinear_iterations

type: Int, optional, default = 12

This parameter sets the maximum number of nonlinear iterations for the Kynema solver.

Kynema.damping_factor

type: Real, optional, default = 0

This parameter sets the numerical damping (time-based) of the Kynema solver. Counterintuitively, full damping corresponds to 0 and no damping corresponds to 1.

Active Wake Control with Joukowsky Disk

There is preliminary support for exploring Active Wake Control (AWC) strategies with the Joukowsky disk model. The current implementation follows Cheung et. al (2024). The following input options allow for enabling AWC:

Actuator.WTG01.awc_angular_frequency

type: Real, optional, default=0

Sets the temporal angular frequency for AWC (in radians)

Actuator.WTG01.awc_amplitude

type: Real, optional, default=0

Sets the amplitude of the forcing term in AWC relative to the axial force

Actuator.WTG01.awc_azimuthal_mode

type: Int, optional, default=0

Sets the azimuthal mode for the AWC (e.g. 0 denotes a pulse mode, 1 denotes a helical mode)

Actuator.WTG01.awc_clocking_angle

type: Real, optional, default=0

Sets the clocking angle to adjust the orientation of the modes in the azimuthal direction (in radians)

ActuatorSourceTagging

It is possible to seed a passive scalar in the flow field at locations where the actuator source term value is above a certain threshold. This is useful for wake visualization and for dynamic adaptation of the mesh to the wake location. This is activated by adding ActuatorSourceTagging to incflo.physics. It has the following input options:

ActuatorSourceTagging.actuator_source_threshold

type: Real, optional, default=0.1

Threshold value for the actuator source term above which the passive scalar will be set to 1.0.

Additional input parameters are transport.passive_scalar_laminar_schmidt and transport.passive_scalar_turbulent_schmidt to set the diffusion of the passive scalar. This can be combined with the FieldRefinement criteria for mesh adaptation:

tagging.labels = tracer
tagging.tracer.type = FieldRefinement
tagging.tracer.field_name = passive_scalar
tagging.tracer.field_error = 0.3 0.3 0.3 0.3

where the field_error is the value above which the cells should be tagged for refinement. Here is an example using the uniform_ct_disk_dynamic_adaptation regression test:

../_images/uniform_ct_disk_dynamic_adaptation.gif

Warning

This is an experimental feature and there is no guidance yet on the values that should be used for the passive scalar and tagging criteria.