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Offshore modelling

Model turbines that can withstand the challenges of the harsh offshore environment.

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Integrated offshore analysis
Arbitrary space frame structures like jackets can be modelled in Bladed using beam elements and flexible joints. Models can be built in the Bladed user interface or imported from third party offshore design tools, such as SESAM or SACS. Foundations can be modelled as linear springs or through non-linear P-Y curve definition.

Bladed can generate irregular airy waves, regular airy or stream function waves. Loads are applied to the model using Morison’s equation. Linear or non-linear extreme waves can be inserted into an irregular sea as a constrained wave.

Inclusion of the wind loads, turbine and jacket model and marine environment in the Bladed calculation allows for fully coupled aero-hydro-servo-elastic simulation. This integrated approach aids the overall optimization of the wind turbine and support structure design. The cost reduction benefits of this approach were explored in DNV GL’s Project FORCE innovation report[link to DNVGL paper].

Jacket loads can be exported to perform fatigue and extreme code checks in ANSYS, SACS or SESAM.

For further information, please read the Bladed offshore support structure module. [link]

Super-element analysis
Not only is it possible to define the jacket structure in Bladed but it is also possible to import a jacket super-element derived from an offshore support structure code, such as DNV GL’s SESAM tool. In this case, the modal mass and stiffness matrices of the jacket, along with the wave loads are imported into Bladed and included in the simulation.

Although the hydro-elastic coupling is excluded, this approach provides an accurate structural response and avoids the need for jacket details to be shared between the foundation designer and the turbine designer or to redefine the jacket and marine environment in Bladed.

Floating turbines
Bladed can model floating wind turbines using a variety of mooring line and hydrodynamic models.

Bladed’s dynamic mooring line model includes multibody system moorings which are connected by several bar components and together with universal joints, form a chain. This allows the mooring dynamics to be fully coupled with the rest of the turbine structure. The mooring lines also attract hydrodynamic loads through Morison’s equation.

To enable faster simulation, simple lookup moorings can be included through the addition of point masses and applied loads. Lookup tables of applied stiffness and damping forces can be pre-calculated for catenary and tension leg moorings.

Advanced hydrodynamics
Structures with very large members may require wave diffraction and radiation to be considered, using a boundary element method to calculate hydrodynamic loads. Large structures’ hydrodynamic properties can be imported from a third party panel method code, such as WAMIT, AWUA or WADAM and then imported into Bladed for use in the simulation. This functionality is included in the Advanced Hydrodynamics Module. [link to module page]