*TOWER INFLUENCE |
 
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*TOWER INFLUENCE |
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To specify the tower influence and drag properties, and the tower mesh settings for the aerodynamic model.
Refer to AeroDyn Overview for further information.
Multiple lines of data, defining the tower properties from the base to the top as follows:
Tower Elevation, Tower Diameter, Tower Drag Force Coefficient, Tower Turbulence Intensity, Tower Buoyancy Coefficient (MHK turbines only)
Tower Elevation, Tower Diameter, Tower Drag Force Coefficient, Tower Turbulence Intensity, Tower Buoyancy Coefficient (MHK turbines only)
:: , :: , :: , :: , ::
Tower Elevation, Tower Diameter, Tower Drag Force Coefficient, Tower Turbulence Intensity, Tower Buoyancy Coefficient (MHK turbines only)
Tower Elevation is measured from the mean water line to the tower node. The Tower Elevation must be entered in monotonically increasing order - from the lowest (tower-base) to the highest (tower-top) elevation. Refer to the Tower Geometry schematic for an illustration.
Tower Turbulence Intensity is only used with the Eames tower shadow model (Tower Shadow Influence=2). It is specified as a fraction (rather than a percentage) of the wind fluctuation.
The tower buoyancy entry is used by OpenFAST to simulate tower buoyancy for MHK turbines. As Flexcom is currently designed to work with wind turbines only, Tower Buoyancy Coefficient should always be set to 0.0.
Input: |
Description |
Tower Elevation: |
The local elevation of the tower node above the mean water line. The Tower Elevation must be entered in monotonically increasing order - from the lowest (tower-base) to the highest (tower-top) elevation. Refer to the Tower Geometry schematic for an illustration. |
Tower Diameter: |
The local tower diameter at the current elevation. |
Tower Drag Force Coefficient: |
The local tower drag force coefficient at the current elevation. |
Tower Turbulence Intensity: |
The turbulence intensity used in the Eames tower shadow model (Tower Shadow Influence set to Eames model) as a fraction (rather than a percentage) of the wind fluctuation. |
Tower Buoyancy Coefficient (MHK turbines only): |
This coefficient is used by OpenFAST to simulate tower buoyancy for MHK turbines. As Flexcom is currently designed to work with wind turbines only, it should always be set to 0.0. |
(a)As the tower is normally tapered from a wide base to a more slender top, it is normally constructed in Flexcom using several Line Sections of different diameter. The mesh density for the structural model is governed by the Line Mesh Generation settings for the line and its sub-sections, while the mesh density for the aerodynamic model is controlled via this *TOWER INFLUENCE keyword. It is not necessary to use the same mesh density for both models, but as a minimum, structural nodes should be placed at elevations which correspond exactly to equivalent nodes in the aerodynamic model. In practice, the structural tower is typically modelled using a certain number of sub-sections of equal length, and the intersection points between these sections serve as the aerodynamic nodes also.
(b)The number of tower nodes in the aerodynamic model, which is governed by the number of tower elevations specified above, must be greater than one. The higher the number, the finer the resolution and longer the computational time. NREL recommend that between 10 and 20 tower nodes be used, to provide a balance between accuracy and computational expense.