Wind turbine noise has become an important issue when developing onshore wind farms as turbines have scale up rapidly in the latest decades. The interest of this project is focused on the characterization and modelling of noise as a source based on the specific physics from wind turbines. A dedicated evaluation of wind turbine noise measurements is carried out in order to know more about the behaviour of it in front different operational conditions. Such study assists to understand trends that can be introduced to improve existing semi-analytical or empirical aeroacoustic models, typically used, in wind turbine noise predictions. The result, enhanced aeroacoustic models with an overall uncertainty reduced when compared to measurements. Therefore, these reliable models can be used for future predictions when scoping new rotors or for performance analysis, i.e. development of low-noise strategies.

The Blade Element Momentum (BEM) method is a widely used model for rotor performance and aeroelastic calculations but it has assumptions in its formulation which limit its accuracy. The theoretical background of these limitations has been studied and an improvement in the form of the Near Wake Model (NWM) has been identified. The model adds near wake vorticity effects to the BEM along with modeling the interdependence of the different annular elements. A coupled model based on the NWM has been developed for steady state analysis of turbine rotors. The model performance has been analyzed for the DTU 10MW Reference Wind Turbine (RWT) and compared to Computational Fluid Dynamics (CFD) simulations. The comparison has been carried out for even and uneven loading distribution. The uneven loading has been modeled by modifying the chord distribution of the blade. Though the aim was to improve the induction distribution, due to the known difficulties of calculating induction from CFD, the aerodynamic loads were investigated rather than focusing on the induction distribution. For an evenly loaded blade, the loads from the coupled model are improved because of the added flow physics. For uneven loading, the coupled model improves upon the standard BEM, but if modified locally over a large section of the blade to represent the uneven loading, it is seen that the coupled model has a large difference compared to CFD. Finally, for slender blades with uneven loading, the model performs reasonably well showing a significant improvement to the BEM in the in-plane forces and an overall improvement in the out-of-plane forces as well when compared to CFD.

The aim of this thesis is to evaluate the influence between the two counter-rotating VAWT rotors with the Double Actuator Cylinder (DAC) model which will be validated against the panel code. The DAC model is developed from the original Actuator Cylinder (AC) model which includes the Modified-Linear (Mod-Lin) correction. The original AC model for modelling single rotor is investigated, modified and validated against the panel code to be sufficient which is the premise for a sufficient DAC model. The original AC model is modified to become a dynamic AC model including Cheng’s modification, flow curvature effect and unsteady aerodynamics. The unsteady aerodynamics is included by coupling the modified Risø dynamic stall model with the AC model. An investigation with Migliore’s conformal mapping method as well as panel code revealed that the modified Risø dynamic stall model implicitly included the flow curvature effects. The derived dynamic AC model is validated to show good agreements with the panel code. It is also revealed that further improvements could be made to the Mod-Lin correction method. The DAC model is finally derived, and the performance on predicting the influence between the two rotors is then investigated.

Currently, the price per kW of offshore wind energy is 55% larger than onshore [38, 52]. Of this price, the rotor corresponds to 22%. To reduce the price of wind energy, it is necessary to investigate wind turbine concepts with scales above 10 MW. The commonly known Horizontal Axis Wind Turbine (HAWT) requires offshore a large support structure. If the turbine is designed to be floating, a deep floater is needed to limit the tilt angle. A possible concept to meet this challenges is the lift-driven Vertical Axis Wind Turbine (VAWT). This thesis aims to optimize the structural design of a VAWT rotor blade and to decrease the mass to area ratio by varying blade shape and structural layout. The choice of mass to rotor area ratio as an optimization function follows from the fact that this area is directly proportional to the energy output while mass drives production and installation costs. The VAWT is defined by an axis perpendicular to the unperturbed flow direction. The rotor geometry is described through a Troposkein shape. It is assumed that the blades carry their own weight leading to a reinforced root region. During operation the blades experience aerodynamic and inertia forces, which are deflecting the blades outwards, leading to an alternation of the aerodynamic loads.The interplay of load alternation and blade deflection could lead to a diverging flutter motion. After a fitting design is obtained, the blade motion has to be inspected for a safe use during operation. The rotor is designed with an adjusted optimizer, originally written by M. Schelbergen [62]. The optimizer uses the Matlab optimization toolbox in combination with Nastran. The modification allows a smooth transition of the thickness of skin, shear web and girder. The airfoil section is varied along the blade. The optimization is based on load cases such as a parked rotor and the maximum up- and downwind forces. These loads are simplified and assumed to vary neither by the motion nor the deflections of the blade. In addition, an aeroelastic model is required to observe the blades’ motion. Through out this thesis two aeroelastic codes were used. The VAWT AeroElastic Multibody Panel Solver (VÆMPS) was created by coupling Sandia National Laboratories OWENS and the near wake panel solver UMPM. However, its computational performance was not satisfying and it was decided to use HAWC2 coupled with an actuator cylinder model to determine the induction.