Bladed’s wind models include various steady and dynamic models necessary to cover all the required load cases.
The deterministic wind components in Bladed include:
- Wind shear following a power law, exponential or user-defined profile.
- Wind direction veer with user-defined profile.
- Wind speed and direction transients following the standard IEC profiles.
- Wake deficit distribution from upstream turbines.
- Tower shadow models for upwind and downwind configurations.
Turbulent wind files can be generated in Bladed as per the following spectral formulations:
- von Karman.
The wind speed at hub height can be matched to measured anemometer values in validation studies. When conducting LiDAR simulations, two wind files can be used together to allow the wind field to evolve in a realistic manner.
As an alternative to the inbuilt wind models users can substitute the wind field created by Bladed with their own dynamic link library (DLL). The DLL should return a wind velocity vector at any requested time and location in three-dimensional global space.
Bladed includes models for regular and irregular wave states and sea currents.
Regular waves follow linear airy or stream function models with the stream function order automatically determined.
Irregular wave states comprise of linear airy waves according to JONSWAP, Pierson Moskowitz or a user-defined spectrum. Constrained linear of stream function waves can be included within the irregular sea state.
By applying Bladed’s external SEA file definition, users can utilizing their own tools to create any sea states comprised of linear wave components and can include directional spreading.
Wave loads are typically applied to the structure through Morison’s equation. A MacCamy-Fuchs correction is used to approximate diffraction effects for large members.
Morison’s equation may not be appropriate for structures with very large members. Wave diffraction and radiation become important and the boundary element method can be used to calculate hydrodynamic loads. A mesh of the structure is used to determine hydrodynamic properties using an external code, such as WAMIT, AQWA or WADAM. This can then be imported to Bladed for use in the simulation. This functionality is included in the Advanced Hydrodynamics Module [link to module page]
Turbines in seismic areas require coupled aero-elastic analysis during earthquakes and this is needed by design standards to accurately determine the effects on turbine loads.
DNV GL’s Bladed tool can generate earthquake acceleration time histories based on a target spectrum. The acceleration time history is shaped according to an appropriate shape function. Alternatively, recorded ground acceleration time histories can be used.
Bladed supports a full 6 degree of freedom time history (3 translational and 3 rotational DoFs) allowing maximum fidelity to investigate realistic earthquake conditions.
This functionality is available through the Bladed seismic module. [link to module page]