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*GENERAL

Purpose

To specify general analysis options.

Theory

Refer to AeroDyn Overview for further information.

Keyword Format

Seven lines of data, defining general analysis options as follows:

ECHO=Input Echo

DTAERO=Aerodynamic Time Step

WAKEMOD=Rotor Wake/Induction Effects

AFAEROMOD=Aerofoil Aerodynamics 

TWRPOTENT=Tower Potential-Flow Influence

TWRSHADOW=Tower Shadow Influence

TWRAERO=Tower Drag Loads

FROZENWAKE=Frozen Wake

CAVITCHECK=Cavitation Check (MHK turbines only)

BUOYANCY=Buoyancy Effects (MHK turbines only)

COMPAA=Aero-acoustics

AA FILE=AA File Name

INPUT FILE=AeroDyn Primary Input File Name

 

 

Set Input Echo to 1 to instruct AeroDyn to echo the contents of the primary, aerofoil, and blade input files (useful for debugging errors in the input files). Set Input Echo to 0 if no input echo is required.

Aerodynamic Time Step is not currently an input, as it is automatically determined by Flexcom's structural analysis timestep, so it assumes a value of DEFAULT always. In standard offshore applications, appropriate time variables are typically dependent on the ambient seastate. For wind turbine modelling, NREL recommend that the solution time step for aerodynamic calculations be set such that there are at least 200 time steps per rotor revolution.

Set Rotor Wake/Induction Effects to 0 if you want to disable rotor wake/induction effects, or 1 to include these effects using the (quasi-steady) blade element momentum theory model. You can also set Rotor Wake/Induction Effects to 2, to use a dynamic blade element momentum theory model (DBEMT), also referred to as dynamic inflow or dynamic wake model. Or set it to 3 to use the free vortex wake model, also referred to as OLAF.

Set Aerofoil Aerodynamics to 1 to include steady blade aerofoil aerodynamics, or 2 to enable unsteady blade aerofoil aerodynamics.

Set Tower Potential-Flow Influence to 0 to disable the potential-flow influence of the tower on the wind local to the blade, 1 to enable the standard potential-flow model, or 2 to include the Bak correction in the potential-flow model.

Set Tower Shadow Influence to 0 to disable to the tower shadow model, 1 to enable the Powles tower shadow model, or 2 to use the Eames tower shadow model. These models calculate the influence of the tower on the flow local to the blade based on the downstream tower shadow model. If the tower influence from potential flow and tower shadow are both enabled, the two influences will be superimposed.

Set Tower Drag Loads to 1 to calculate wind drag loads on the tower, or 0 to disable these effects.

During linearisation analyses with AeroDyn coupled OpenFAST and BEM enabled (Rotor Wake/Induction Effects = 1), set the Frozen Wake flag to 1 to employ frozen-wake assumptions during linearisation (i.e. to fix the axial and tangential induces velocities, and, at their operating-point values during linearisation) or 0 to recalculate the induction during linearisation using BEM theory.

Set Cavitation Check to 1 to perform a cavitation check for MHK turbines (disabled by default). If Cavitation Check is 1, Aerofoil Aerodynamics must be set to 1 because the cavitation check does not function with unsteady airfoil aerodynamics. As Flexcom is currently designed to work with wind turbines only, Cavitation Check should always be set to 0.

Set Buoyancy Effects to TRUE to calculate buoyant loads on the blades, tower, nacelle, and hub of an MHK turbine (disabled by default). If Buoyancy Effects is TRUE, the MHK flag in the AeroDyn or OpenFAST driver input file must be set to 1 or 2 to indicate an MHK turbine is being modeled. As Flexcom is currently designed to work with wind turbines only, Buoyancy Effects should always be set to FALSE.

Set Aero-acoustics to 1 to run aero-acoustic calculations. This option is only available for Rotor Wake/Induction Effects = 1 or 2. Refer to NREL AeroDyn documentation for information on how to use this feature.

The AA File Name input is used to specify the input file for the aeroacoustics sub-module. Refer to NREL AeroDyn documentation for information on how to use this feature.

The AeroDyn Primary Input File Name input is used to specify the name of the AeroDyn primary input file that is generated. The file name should have a .dat file extension. This entry is optional and, if omitted, defaults to the name of the keyword file with the .dat extension.

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