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: TurbineFastLine, TurbineFastDisk, and FixedWingLine.

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, thicness 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

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

Actuator.FixedWingLine.fllc_relaxation_factor

type: Double

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

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

Actuator.FixedWingLine.pitch

type: Real number, optional

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.

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 avery 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.FixedWindLine.velocity

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

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

Actuator.FixedWindLine.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.FixedWindLine.sine_period

type: Real number, mandatory when motion_type = linear

This value specifies the temporal period of the sine signal.

TurbineFastLine

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.