On Control and stabilisation of floating wind platforms with the help of CFD analysis and the Magnus effect

Sammanfattning: With new technologies and possibilities arising both in the renewable energy sector as well as in the field of Computational Fluid Dynamics, this thesis describes the simulation of vortex- induced vibrations for floating wind turbine platforms. The aim is to control and stabilize floating wind platforms with the help of CFD and the Magnus effect. The Magnus effect shall hereby be used to reduce the wakes behind the cylinder and thereby not only move the cylinder, but also reduce vibrations. Therefore this thesis consists of three main sets of experiments. The first set simulates vortex-induced vibrations for low Reynolds number flow and compares the results to existing research results. The second set of experiments examines VIV for high or supercritical Reynolds number flow and the last set of experiments adds rotation to the platform, hence studies the impact the Magnus effect has on stabilisation and position controlling. The simulations are conducted on a fully submerged cylinder floating in a virtual test bassin, moored by a two-dimensional spring damper system. The numerical method for solving the incompressible Navier-Stokes equations is the Eulerian cG(1)cG(1), a finite element method (FEM) based on the weak formulation of the former. The spring damper equations are solved using a trapezoidal rule and the coding was based on the Unicorn framework in FEniCS. Calculations were done on a Cray XC40 system at KTH Stockholm. Results showed that the above method in many cases produced results closer to physical results than previous numerical research. It also showed that the Magnus effect can be used even for supercritical Reynolds number flow to stabilise the platforms by reducing wakes behind them. It further shows that this effect is in close relation to the shift of the platform and mostly depends on the natural frequency, the inflow velocity and the rotation speed.