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If at least one reference wind turbine is available, which provides sufficient information about the wind turbine loads, the loads acting on the neighbouring wind turbines can be predicted via an artificial neural network (ANN). This research explores the possibilities to apply such a network not only within a wind park but on turbines located at different sites. Following the idea to develop a tool to forecast the particular loads of any wind turbine in the field without the need to install additional measuring systems, a model has been developed needing only signals contained in the Supervisory Control and Data Acquisition (SCADA) data as input signals.

The installation of floating wind farms in deeper water is encouraged by the stronger and steadier wind, the lower visibility and noise impact, the absence of road restrictions, but also the absence or shortage of shallow water. In the summer of 2009, the first large-scale floating wind turbine ”Hywind” was installed. Hywind is a spar-buoy concept with three catenary mooring lines. The experience with modeling floating turbines is still limited. Furthermore, existing models for the design of offshore wind turbines are highly complex as they focus - by definition - mostly on the forces of the wind on the turbine. The correctness and applicability of existing simulation models for the design of floating wind turbines can therefore not be assumed a-priori and need to be researched. This requires that the driving physical processes governing the behaviour of floating wind turbines are investigated first. For this purpose, a new basic model A.T.FLOW has been developed. The requirement of A.T.FLOW is that it incorporates the most significant physical processes so as to be able to provide insight into the dominant physical behaviour of spar-type floating wind turbines. Assumptions have been made that illustrate the limitations of A.T.FLOW. Various verification methods show that the model simulates load cases as expected and is a useful tool for assessing the physical behaviour of spar-type floating wind turbines. The coming two years the body forces and behaviour of the operating full-scale Hywind demo project is monitored. This data should be used to further test and validate A.T.FLOW and to guide further development of the model.

The scope of this work was to investigate radial flow component for a Horizontal Axis Wind Turbine in axial flow conditions and to assess its impact on the turbine operation. This was done by means of Particle Image Velocimetry and numerical simulation with a 3D unsteady potential-flow panel model. A direct comparison between the numerical and experimental radial velocity results show differences in the tip and root regions. These differences have important implications on the wake development just at the moment of release of the tip vortex. Moreover, the impact of the radial velocities on the blade loading has been studied using the numerical results. The contribution of the radial velocity to the normal load on the blade is only slightly appreciable in the tip and root regions of the blade. However, as the numerical model does not account for viscous effects, further analysis of impact on boundary layer development is necessary.

This paper sets out to describe the measurements and computations to construct three components of velocity field around the blade. The primary aim of the measurements was to gain insight into the physics of the flow field produced by a horizontal axis wind turbine-HAWT blade. Stereo Particle Image Velocimetry experiments were performed on a two-bladed HAWT rotor in the open jet facility. Three components of velocity on 2D planar measurement planes were obtained from the defined field of views. The three components of velocity at the different radial positions are analysed in the present paper by comparing the experimental results with the panel code results. Besides having an insight about the flow field around the blade section, this comparison enables to improve and validate the panel code. The measurements show very well agreement with the computations except at the tip trailing edge region which is expected. The key observation of this work is inboard motion of the tip vortex. Also, clear outward motion of the radial flow on the suction side of the inboard sections of the blade is observed in the measurements and computations.

The linear scaling laws for upscaling wind turbine blades show a linear increase of stresses due to the weight. However, the stresses should remain the same for a suitable design. Application of linear scaling laws may lead to an upscaled blade that may not be any more a feasible design. In this paper a non-linear upscaling approach is presented with the aim of keeping the stresses in the upscaled blade the same as the reference blade. The stresses due to the weight, aerodynamics and centrifugal forces are taken into account and the blade is modeled as a beam with equivalent structural properties. This new methodology is used to upscale the 5 MW NREL wind turbine blade to a 20 MW wind turbine blade. As a result, a 20 MW wind turbine blade is obtained in which the stresses are the same as the 5 MW blade. This provides initial blade design solution for optimization studies that is feasible and enables the designer to explore other interesting aspects of larger scale wind turbines.

A detailed quantitative description of the aerodynamics of a horizontal axis wind turbine (HAWT) is difficult due to complexity of the flow field. Several methods from experimental to analytical are used to investigate the aerodynamics of a HAWT. In the present study, a wind tunnel experiment and computational fluid dynamics (CFD) simulations are used to explore the expansion of the wake. 2D actuator disc (AD) simulations are compared with the wind tunnel experiments. To understand the aerodynamic behavior of a model wind turbine blade, a detail flow field measurements in chordwise-spanwise directions and in the wake have been done. The measurements are performed on a 2 bladed rotor by means of Stereo Particle Image Velocimetry (Stereo PIV) in an open jet wind tunnel. In this paper, the velocity measurements performed in the wake region of the blade is presented. Actuator disc simulations are performed by applying a constant pressure jump on a permeable disc of zero thickness. Actuator disc simulations are carried out by using FLUENT 6.3.26 with the incompressible version of the Reynolds Averaged Navier-Stokes (RANS) equations. By validating the simulations with the experimental results, one may conclude that the unsteady CFD modeling works correctly and the wake expansion of the prescribed model is affected by the geometry of the Open Jet Facility (OJF).

The purpose of this paper is to integrate the controller design of wind turbines with structure and aerodynamic analysis and use the final product in the design optimization process (DOP) of wind turbines. To do that, the controller design is automated and integrated with an aeroelastic simulation tool. This integrated tool is linked with an optimization engine. The automated controller has two built-in control algorithms; a generator-torque controller and an above rated pitch-controller. This new tool is used in the DOP of the 5MW NREL research wind turbine. To show how this method works some parameters of both the generatortorque controller and the pitch-controller are introduced as design variables in the DOP. As the result of changing controller related design variables within each optimization iteration, the values of the objective function and the design constraint also change. This shows that by introducing the controller’s parameters as design variables in the DOP a more realistic assessment of the objective function and constraints is possible that helps the optimizer to search for better solutions.

A wind turbine blade has a complex shape and consists of different elements with dissimilar material properties. To do any aeroelastic simulation, the structural properties of the blade such as stiffnesses and mass per unit length should be known in advance, and extracting these properties is a difficult task. This paper presents an analytical model to extract these structural properties in a simple way. It starts with calculating an equivalent material property of the cross section using weighting method. Then the centroid of each section is obtained. Next the second moment of inertia of each element relevant to its local coordinates system is calculated and transferred to the centroid of the section using parallel axis theorem. A coordinate transformation is employed to rotate these second moment of inertias around any arbitrary axis. Finally, flapwise and edgewise stiffnesses are found by multiplying the equivalent modulus of elasticity to the second area moment of inertia in each section. Mass per unit length is calculated by multiplying the equivalent density to the real area of each section. The method is verified with the structural properties of a commercial 660 kW wind turbine blade. Despite the simplicity of the method the results show a good agreement.

Wind energy in the urban environment faces complex and often unfavorable wind conditions. High turbulence, lower average wind velocities and rapid changes in the wind direction are common phenomena in the complex built environments. A possible way to improve the cost-efficiency of urban wind turbines is the application of flowenhancing structures on or near the turbines. For horizontal axis wind turbines (HAWTs), applying a diffuser has shown to have a beneficial impact on the power production, but it is still under development. For a vertical axis wind turbine (VAWT) it is expected that flow augmentation will also strongly increase the performance of the turbine, but very little research has been done in this field. The purpose of this research is to investigate the effects of a diffuser on the airflow through a VAWT. In order to investigate these effects, the turbine (with and without diffuser) is simulated using a 2-D unsteady free-wake potential-flow panel model. The local flow field, local angles of attack, shed vorticity, the shape and strength of the wake, and the rotor torque are investigated for both the case with and without the diffuser. The diffuser used in this research consists of two mirrored airfoil cross-sections. The size of the duct-opening in which the turbine operates is varied. This work shows that unlike for a 1-D actuator disc analysis, the area ratio B of the diffuser exit with respect to the diffuser nozzle area is not the only driving factor in the augmentation of the rotor torque of the VAWT. More important are the effect of the directional change of the rotor inflow and the faster downstream transport of the shed vorticity.