Demonstration of a coupled floating offshore wind turbine analysis with high-fidelity methods

Abstract

This paper presents results of numerical computations for floating off-shore wind turbines using, as an example, a machine of 10-MW rated power. The aerodynamic loads on the rotor are computed using the Helicopter Multi-Block flow solver developed at the University of Liverpool. The method solves the Navier-Stokes equations in integral form using the arbitrary LagrangianEulerian formulation for time-dependent domains with moving boundaries. Hydrodynamic loads on the support platform are computed using the Smooth-ed Particle Hydrodynamics method, which is mesh-free and represents the water and floating structures by a set of discrete elements, referred to as particles. The motion of the floating offshore wind turbine is computed using a Multi-Body Dynamic Model of rigid bodies and frictionless joints. Mooring cables are modelled as a set of springs and dampers. All solvers were validated separately before coupling, and the results are presented in this paper. The importance of coupling is assessed and the loosely coupled algorithm used is described in detail alongside the obtained results.

Aeroelastic analysis of a floating offshore wind turbine in platform‐induced surge motion using a fully coupled CFD‐MBD method

“…On the other hand, impacts of platform motions induced by waves and current on wind turbine aerodynamics have been investigated extensively using CFD methods either by imposing prescribed periodic motions to wind turbines [19][20][21][22] or via performing fully coupled aero-hydrodynamic analysis. [23][24][25] These CFD studies demonstrated that platform motions greatly affected wind turbine aerodynamics as well as its wake. However, they only focused on wind turbines with rigid blades.…”

“…Currently, these studies are limited to fixed‐bottom wind turbines without considering platform motions in FOWT applications. On the other hand, impacts of platform motions induced by waves and current on wind turbine aerodynamics have been investigated extensively using CFD methods either by imposing prescribed periodic motions to wind turbines or via performing fully coupled aero‐hydrodynamic analysis . These CFD studies demonstrated that platform motions greatly affected wind turbine aerodynamics as well as its wake.…”

CFD Investigation of a Complete Floating Offshore Wind Turbine

“…The MBDM was validated using simple mechanical systems of known solution as presented in Leble and Barakos (2016) like 2D and 3D slider-crank mechanisms. The gyroscopic wheel mechanism was used to validate that the gyroscopic effect is properly accounted for in the multi-body formulation.…”

“…FOWT model consists of three mooring lines and two rigid bodies: the rotor (blue) and combined body representing nacelle, tower and support (red). Adapted from Leble and Barakos (2016) that design, the present support is simplified to be symmetric with respect to the location of the tower and the floats are connected to the base of the tower with a solid frame. The size of the tower is taken from Bak et al (2013), and the dimensions of the support were calculated to provide sufficient buoyancy.…”

“…Waves are generated to represent the specific sea state corresponding to a given wind speed. Based on the measurements of annual sea state occurrences in the North Atlantic and North Pacific (Lee et al 1985), the wind speed of 11 m/s corresponds to a sea state 4 with a mean wave height of 1.88 m and a period of 8.8 s. Adapted from Leble and Barakos (2016) …”