Input:

Description

BEM Algorithm:

The options are No Sweep Pitch Twist (legacy) for the old AeroDyn BEM implementation using the NoSweepPitchTwist coordinate system, and Polar (recommended) for the new AeroDyn BEM implementation using the local staggered polar grid coordinate system, which is more suitable for large coning. This implementation also includes an optional momentum correction that is important for large skew.

Skew Model:

The options are Glauert's Skew Model (recommended), which has includes a momentum correction and a velocity redistribution model, No Skew Model (not recommended), or Remove Non-Normal Component to discard the non-normal component (for linearization).

Skew Moment Correction:

Set Skew Moment Correction to True to enable skew moment correction or False to disable this calculation.

Skew Velocity Redistribution:

The options are Glauert/Pitt/Peters (recommended) to enable the induced velocity redistribution model or No Redistribution to disable this calculation.

Skewed-Wake Correction Factor:

Enter a scaling factor to use in the Glauert/Pitt/Peters velocity redistribution model, or enter Default to use the default value of 15 π / 32.

Prandtl Tip-Loss:

This option allows you to include the Prandtl tip-loss model, or to disable it.

Prandtl Hub-Loss:

This option allows you to include the Prandtl hub-loss model, or to disable it.

Tangential Induction:

This option allows you to include tangential induction (from the angular momentum balance) in the BEM solution, or to neglect it.

Axial-Induction Drag:

This option allows you to include drag in the axial-induction calculation, or to neglect it.

Tangential-Induction Drag:

This option allows you to include drag in the tangential-induction calculation, assuming tangential induction itself is being included, or to neglect it.

Convergence Threshold:

The convergence threshold for the iterative nonlinear solve of the BEM solution. The nonlinear solve is in terms of the inflow angle, but the convergence threshold represents the tolerance of the nondimensional residual equation, with no physical association possible. ‘DEFAULT’ may be specified rather than a numerical value, allowing AeroDyn to select an appropriate default value as recommended by NREL.

Maximum Iterations:

The maximum number of iterations steps in the BEM solver. If the residual value of the BEM solver is not less than or equal to Convergence Threshold in Maximum Iterations, AeroDyn will exit the BEM solver and return an error message.

Sector Averaging:

This option allows you to enable shear corrections to the BEM algorithm by limiting fluctuations associated with variations of wind speed as the blade rotates, or to disable these corrections. The method uses sectors expanding forward and backward relative to the current azimuth of the blade. The velocity is averaged within this sector by attributing different weighting at different points in the sector.

Sector Average Weighting Function:

Specify a value of 1 to use a uniform weighting function for sector averaging within a sector centered on the blade.

Number of Points:

This input control the number of points per sector (default=5).

Backward Azimuth

This input determines the backward azimuth angle relative to blade where the sector starts (defaults is -60 degrees).

Forward Azimuth

This input determines the forward azimuth angle relative to blade where the sector starts (defaults is +60 degrees).