Actuator line/sector model

The actuator line model (ALM) is implemented by applying body forces to the flow field. These forces are calculated by sampling the velocity field along the blades. At each blade point, the lift and drag forces are read from precomputed tables and applied to the flow field using a Gaussian filter kernel at a scale \(\epsilon \).

Settings

The ALM in LESGO is implemented in a similar form as the SOWFA package from NREL, including the input files. Input files for the NREL 5MW reference turbine are located in “inputATM.” The turbine array is specified in “inputATM/turbineArrayProperties.” For example:

! Global Properties
numberOfTurbines        1
outputInterval          1
updateInterval          1

! First turbine
TURBINE_1 {
turbineType             "NREL5MWRef"
baseLocation            190.0, 315.0, 225.0
numBladePoints          60
epsilon                 12.5
sampling                "atPoint"
rotationDir             "cw"
Azimuth                 232.0105
RotSpeed                9.155
Pitch                   0
NacYaw                  0
fluidDensity            1.23
numAnnulusSections      1
annulusSectionAngle     0.
nacelleFlag             false
nacelleCd               1.
TSR                     6.
tipALMCorrection        .true.
optimalEpsilon          0.25
}

Each turbine type is defined in a file that specifies basic details about the gemoetry of the turbine, the turbine controller, and definitions of the blades. The lift and drag lookup tables are located in the folder “inputATM/AeroData.”

Output

All output files relating to the turbines can be found in the “turbineOutput” folder. The following The following quantities are written for each turbine in the files “turbineOutput/TURBINE_#/…”.

Drag coefficient
Drag force
Lift coefficient
Lift force
Thrust force
Tangential force
Axial force
Axial velocity
Relative velocity
Tangential velocity
Yaw angle
Pitch angle
Rotational speed
Power

References

Martínez-Tossas LA, Churchfield M, Meneveau C. “Large Eddy Simulation of wind turbine wakes: detailed comparisons of two codes focusing on effects of numerics and subgrid modeling.” Journal of Physics: Conference Series 625 (2015). 012024.

Martínez-Tossas LA, Stevens RJAM, Meneveau C. “Wind farm large-eddy simulations on very coarse grid resolutions using an actuator line model.” 34th Wind Energy Symposium (2016). San Diego, California. AIAA Paper No. 2016-1261.