*BLADE GEOMETRY |
 
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*BLADE GEOMETRY |
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To specify the geometry of wind turbine blades.
Refer to Turbine Geometry for further information.
A block of lines starting with the blade name, followed by as many lines as necessary to completely define the blade geometry as a function of length (span) along each blade. The entire block of data may then be repeated for other blades. Note that all blades must have the same number of sections.
Line defining the blade name:
BLADE NAME=Blade Name
Line defining the blade properties at a particular value of blade span (this line may be repeated as often as required):
Blade Span, Aerodynamic Centre Out-of-Plane Offset, Aerodynamic Centre In-Plane Offset, Curvature Angle, Twist Angle, Chord Length, Aerofoil Index, Blade Buoyancy Coefficient (MHK turbines only), Buoyancy Centre Normal Offset (MHK turbines only), Buoyancy Centre Tangential Offset (MHK turbines only)
Refer to the Blade Geometry schematics for an illustration of the various inputs. Each blade definition must have properties defined for at least two values of blade span. The Blade Span entries must be entered in monotonically increasing order, from the most inboard to the most outboard. The first span must be zero and the last span should be located at the blade tip. Valid values of Aerofoil Index are numbers between 1 and the Total Number of Aerofoil Input Files.
The blade buoyancy entries are used by OpenFAST to simulate tower buoyancy for MHK turbines. As Flexcom is currently designed to work with wind turbines only, the three buoyancy entries should always be set to 0.0.
The rotor is assembled according to the blade selections and related information defined in the *TURBINE ROTOR keyword. Flexcom creates a node in the finite element discretisation corresponding to each blade span position defined in the *BLADE GEOMETRY keyword. These nodes are connected sequentially using finite elements whose structural properties are governed by the inputs in the *BLADE STRUCTURE keyword. The structural properties are assumed constant along each element, and determined using linear i between the element centrepoint and the nearest available sectional definitions.
Input: |
Description |
Blade Name: |
The name of the blade. Note that the same blade names should be used in the *BLADE GEOMETRY, *BLADE STRUCTURE and *TURBINE ROTOR keywords. |
Blade Span: |
The distance along the (possibly preconed) blade-pitch axis from the root. This is illustrated by 'BlSpn' in Blade Geometry - Side View. The span entries must be entered in monotonically increasing order, from the most inboard to the most outboard. The first span must be zero and the last span should be located at the blade tip. Each blade definition must have properties defined for at least two values of blade span. |
Aerodynamic Centre Out-of-Plane Offset: |
The local out-of-plane offset (when the blade-pitch angle is zero) of the aerodynamic center (reference point for the aerofoil lift and drag forces), normal to the blade-pitch axis, as a result of blade curvature. This is illustrated by 'BlCrvAC' in Blade Geometry - Side View. The offset is measured positive downwind; upwind turbines have negative offsets for improved tower clearance. |
Aerodynamic Centre In-Plane Offset: |
The local in-plane offset (when the blade-pitch angle is zero) of the aerodynamic center (reference point for the aerofoil lift and drag forces), normal to the blade-pitch axis, as a result of blade sweep. This is illustrated by 'BlSwpAC' in Blade Geometry - Front View. A positive offset is opposite the direction of rotation. |
Curvature Angle: |
The local angle (in degrees) from the blade-pitch axis of a vector normal to the plane of the aerofoil, as a result of blade out-of-plane curvature (when the blade-pitch angle is zero). This is illustrated by 'BlCrvAng' in Blade Geometry - Side View. Curvature angle is measured positive downwind; upwind turbines have negative curvature angles for improved tower clearance. |
Twist Angle: |
The local aerodynamic twist angle (in degrees) of the aerofoil. It is the orientation of the local chord about the vector normal to the plane of the aerofoil, positive to feather, leading edge upwind. The blade-pitch angle will be added to the local twist. |
Chord Length: |
The local chord length. |
Aerofoil Index: |
This entry specifies which aerofoil data input file is to associated with this local blade span position. Valid values are numbers between 1 and the Total Number of Aerofoil Input Files. Multiple blade nodes can use the same aerofoil data. |
Blade Buoyancy Coefficient (MHK turbines only): |
This coefficient is used by OpenFAST to simulate blade buoyancy for MHK turbines. As Flexcom is currently designed to work with wind turbines only, it should always be set to 0.0. |
Buoyancy Centre Normal Offset (MHK turbines only): |
The offset of the blade centre of buoyancy from the aerodynamic centre in the direction normal to the chord (positive pointing toward the suction side of the blade). As Flexcom is currently designed to work with wind turbines only, it should always be set to 0.0. |
Buoyancy Centre Tangential Offset (MHK turbines only) |
The offset of the blade center of buoyancy from the aerodynamic center in the direction tangential to the chord (positive pointing toward the trailing edge of the blade. As Flexcom is currently designed to work with wind turbines only, it should always be set to 0.0. |
(a)You can define as many blades as you wish in the *BLADE GEOMETRY and *BLADE STRUCTURE keywords. Only the blades which you reference in the *TURBINE ROTOR keyword will be used in the model.
(b)Flexcom creates a node in the finite element discretisation corresponding to each blade span position defined in the *BLADE GEOMETRY keyword. These nodes are connected sequentially using finite elements whose structural properties are governed by the inputs in the *BLADE STRUCTURE keyword. The structural properties are assumed constant along each element, and determined using linear interpolation between the element centrepoint and the nearest available sectional definitions.