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The main objective is intended to be the experimental investigation in wind tunnel to determine the structure of the real flow in a fixed Savonius wind turbine. A secondary objective of this experimental study will be to obtain the aerodynamic performance of studied wind turbine and also information about velocity field around the rotor. Due to its principle of operation and the continuous variation of flow angle with respect to blades, strong unsteady effects including separation and vortex shedding are observed in a Savonius wind turbine . The flow analysis helps to qualify the design of the wind turbine and to assess the quality of numerical simulations, data concerning the mechanism of torque creation, the vortex structure downstream of the rotor and aerodynamic performance. The experimental investigation in wind tunnel is carried out using flow visualization technique.The main tasks will be:- State of the art of efficient wind turbines- Theoretical study of a Savonius wind turbine- Study of the different available geometries of Savonius to the wind tunnel- Choose the best experimental method for the flow visualization and learn how to use it- Design and construction of the Savonius wind turbine model and the test bench- Experimental running- Results analysis

The flow around the blade of a horizontal axis wind turbine wind tunnel model, operating at its optimal tip speed ratio in axial flow, has been investigated by means of stereoscopic particle image velocimetry (SPIV). The aim was to assess the possibility of measuring the loads impinged on the blade, using the acquired velocity field and its spatial derivatives. Thus, the three-dimensional (3D) velocity field and the pressure distribution surrounding the blade, as well as the aerodynamic loads, responsible for thrust and torque, were obtained with a non-intrusive method. The SPIV equipment was mounted on a traverse system and provided with phase-locked velocity planes perpendicular to the blade axis, scanning the blade from the root to the tip, at a fixed azimuthal position. The obtained velocity fields were used to estimate the pressure distribution and the aerodynamic loads on each plane, using a 3D formulation. Finally, these results were compared and discussed with similar results obtained computationally with a panel method model, showing good consistency. In the future, the proposed methodology could be used to study relevant topics such as active load control techniques, rotational augmentation, dynamic stall phenomena and the aerodynamics of small wind turbines operating at low Re numbers, among others. The processed and averaged flow fields from the experimental SPIV data are made available online to the reader. See appendix for description of the files.

La generación de energía eléctrica a partir de energía cinética procedente del viento ha cobrado importancia, en los últimos años, debido al aumento de la demanda energética global y a la creciente sensibilización medioambiental. En este contexto, el estudio aerodinámico juega un papel fundamental estimando la producción energética anual. El presente trabajo contiene toda la información necesaria para implementar un método de cálculo de fuerzas aerodinámicas. El uso de un modelo no estacionario (Beddoes-Leishman) supone una mejora sustancial en el modelo original, formado por la combinación de la teoría de disco actuador y elemento de pala (BEM). Las limitaciones propias del modelo original motivan a estudiar nuevos modelos complementarios que aparecen para corregir dichas limitaciones. Tras la realización de un código de cálculo en Matlab, los resultados son validados mediante una comparativa de resultados analíticos y experimentales obtenidos sobre el modelo de turbina de TUDelft. Los resultados son positivos, por lo que el programa realizado puede ser utilizado de manera satisfactoria en la estimación de fuerzas aerodinámicas. Energy harvesting from wind’s kinetics energy has emerged as a major theme in recent years due to rising energy demand and growing environmental awareness. In this context, the aerodynamic study plays an important role estimating the annual energy yield. The present work contains all the information necessary to implement a calculation method for the aerodynamic forces. An unsteady model (Beddoes-Leishman) represents a substantial improvement in the original model based on the combined Momentum and Blade Element Theory (BEM). The inherent limitations of the original method motivate us to study new complementary models which make possible to correct such limitations. Following the development of a calculation code in Matlab, the results are validated by a comparison between simulation and experimental results obtained on the TUDelft wind turbine. The results are positive and the code can either be used on its own as a complementary tool in the estimation of forces.

The expected exhaustion of fossil sources of energy requires the improvement of other renewable sources, such as wind turbines. Vertical-axis wind turbines present very attractive performance characteristics but extremely complicated aerodynamics. Therefore, research is still needed on this field. A code is developed in order to apply the blade element momentum theory to these wind turbines. BEMT is shown to give considerably reliable results, compared to its fast convergence. BEMT is improved with dynamic stall and wake interaction modifications, in order to include more physical effects. Modified BEMT models will help obtain fast and qualitatively reliable data on VAWT performance. Comparisons with other authors prove that the generated code provides data that are close to the real results. Outgoing

El objeto de este estudio es adquirir conocimientos sobre los perfiles flatback y con ellos generar y optimizar un nuevo diseño de perfil de este tipo. Estos perfiles, que tienen un potencial uso en las palas de los aerogeneradores, reemplazarían a los perfiles gruesos que son usados en la raíz de cada pala del aerogenerador y presentan deficiencias aerodinámicas debido a su gran espesor Collect available literature on current flat back airfoils.Study conventional airfoils used in current wind turbines blade design and characterise its aerodynamic properties.Obtain flat back airfoils from this conventional sections and optimise them to obtain better aerodynamic characteristics.

This thesis aims to analyze the importance of airfoils geometry in the yield of wind turbines using computational fluid dynamics (CFD) approach. It pretends to interpret the most important aerodynamic design features of the rotor, and aerodynamic parameters associated with blades airfoils geometry, related with the improvement of wind turbines efficiency for vertical and horizontal axis generators. Moreover the project pretends to explain basic concepts of wind energy converters of both generators named before, and the physical principles of wind energy conversion. All this study will be proven using some specific cases of airfoil shapes for aircraft wings standardized by the National Advisory Committee for Aeronautics (NACA)1. These different shapes will be simulated through CFD changing the mainly influent variables. The numerical simulation of the flow field around the blades will be conducted with ANSYS® Fluent Software2. Finally, the conclusions obtained by the simulation will be compared with the physical explanation demonstrated before, thus obtaining information about how to optimize the airfoil shape. Outgoing

In order to accurately model large, advanced and efficient wind turbines, more reliable and realistic aerodynamic simulation tools are needed. In this project a code to compute the aerodynamics of a Horizontal Axis Wind Turbine is developed. The formulation is based on Prandtl's lifting line theory and assuming a helical prescribed wake of the rotor. To develop this code, another code to compute the wing aerodynamics based in Prandtl's lifting line is developed. This wing code is also explained and validated in this project. Furthermore, the formulation of the numerical lifting line and its adaptation to compute the wing and rotor aerodynamics is presented. The HAWT code is expected to predict the tangential and normal forces to the rotor plane and the results coming from numerical and experimental comparisons are presented. Finally, further code improvements are suggested