floris.core.wake_turbulence.crespo_hernandez

Classes

CrespoHernandez([initial, constant, ai, ...])

CrespoHernandez is a wake-turbulence model that is used to compute additional variability introduced to the flow field by operation of a wind turbine.

class floris.core.wake_turbulence.crespo_hernandez.CrespoHernandez(initial=0.1, constant=0.9, ai=0.8, downstream=-0.32)

CrespoHernandez is a wake-turbulence model that is used to compute additional variability introduced to the flow field by operation of a wind turbine. Implementation of the model follows the original formulation and limitations outlined in [1].

Note: The values for default parameters provided here differ from those in :cite:`cht-crespo1996turbulence. Following their recommendations, the default parameters would instead be:

• initial: -0.0325*

• constant: 0.73

• ai: 0.8325

• downstream: -0.32

• The "initial" parameter is given as -0.0325 in [1],

but the negative exponent is not clear in the scans of the paper found on the internet, and several subsequent paper cite the exponent as positive (0.0325). This discrepancy is noted in [19]. Moreover, [19] argues that positive values for this exponent are not representative of the physical phenomena occurring. For more details, see NREL/floris#773. Nonetheless, the default value here is set to 0.1 for consistency with previous FLORIS versions. The default value may be updated in a future release.

Args:

parameter_dictionary (dict): Model-specific parameters.

Default values are used when a parameter is not included in parameter_dictionary. Possible key-value pairs include:

• initial (float): The exponent on the initial ambient turbulence intensity.

• constant (float): The constant used to scale the wake-added turbulence intensity.

• ai (float): The axial induction factor exponent used in in the calculation of wake-added turbulence.

• downstream (float): The exponent applied to the distance downstream of an upstream turbine normalized by the rotor diameter used in the calculation of wake-added turbulence.

References:

[1] (1,2,3,4)

A. Crespo and J. Hernández. Turbulence characteristics in wind-turbine wakes. Journal of wind engineering and industrial aerodynamics, 61(1):71–85, 1996.

Parameters:

• initial (float)

• constant (float)

• ai (float)

• downstream (float)

initial: float

constant: float

ai: float

downstream: float

prepare_function()

Return type:

dict

function(ambient_TI, x, x_i, rotor_diameter, axial_induction)

Return type:

None

Parameters:

• ambient_TI (float)

• x (ndarray)

• x_i (ndarray)

• rotor_diameter (float)

• axial_induction (ndarray)