Design and Calibration of a Wind Tunnel Facility for the Study of Active Flow Control on Wind Turbine Blades

Our group at Syracuse University has been working under Professor Mark Glauser as part of a wind consortium with the University of Minnesota and United Technologies Research Group. Our component of this project will be to develop a system which can be imbedded in an airfoil which can increase the efficiency of the airfoil. Along with developing this “intelligent blade,” we will also be characterizing the affect our control system will have on aerodynamic noise. To accomplish these goals, Syracuse University’s anechoic jet facility was remodeled to incorporate a wind tunnel within which we could run our experiments. Upon the completion of the facility, calibration experiments were performed on the measurement devices which we are using in during our testing of the airfoil. Calibration data was collected from the force balance, upon which the airfoil is mounted, the pressure transducers which are embedded inside the airfoil. Still to be collected are the sound characteristics of our chamber when the facility is running. For the control system which we will be using to improve the airfoils efficiency, we are referencing past work done by Syracuse University Ph. D. students who have developed control systems and algorithms in the past

STRUCTURAL CONTROL OF OFFSHORE WIND TURBINES USING PASSIVE AND SEMI-ACTIVE CONTROL

Offshore wind energy has the potential to generate substantial electricity production compared to onshore locations, due to the high-quality wind resource. Offshore wind turbines must endure severe offshore environmental conditions and be cost effective, in order to be sustainable. As a result, load mitigation becomes crucial in successfully enabling deployment of offshore wind turbines. A direct approach to reduce loads in offshore wind turbines is the application of structural control techniques. So far, the application of structural control techniques to offshore wind turbines has shown to be effective in reducing fatigue and extreme loads of turbine structures. However, the majority of previous research regarding the application of structural control to offshore wind turbine noted the needs for the high-fidelity analysis for structural control using a computer aided engineering (CAE) tool, such as FASTv8. In this dissertation, a structural control module coupled with FASTv8 is developed to meet the needs for high-fidelity analysis of structural control techniques for various OWTs. In addition, the developed control module is updated to analyze various structural control devices operating both passively and semi-actively. The dynamics of an omni-directional pendulum-type tuned mass damper and orthogonal tuned liquid column dampers (TLCDs) are mathematically modeled and incorporated into the structural control module. With the developed control module, several structural control devices are optimized through a variety of techniques (parametric study, exhaustive search and multi-objective optimization). Solving optimization problems not only provides the parameters for each control device that can be applicable to other multi-megawatts offshore wind turbines, but also provides insight into the effects of design variables on the control performance. Site-specific meteorological and oceanographic data that consists of a combination of wind and wave data are processed and compiled in order to establish key design load cases. With the optimal designs of structural control devices, non-linear fully-coupled time marching simulations are conducted by running a series of design load cases in order to investigate the impacts of passive and semi-active structural control on improving fatigue and extreme behaviors of fixed-bottom and floating offshore wind turbines. The simulation results demonstrate the effectiveness of various structural control techniques on reducing fatigue and extreme loadings

Trailing-edge flow control for wind turbine performance and load control

This paper reports an investigation into the performance of trailing-edge flow control devices on horizontal axis wind turbines by solving the three dimensional Reynolds averaged Navier-Stokes equations in the rotational framework. The validation case selected for this work is the NREL Phase VI blade with wind tunnel experimental data. The trailing-edge flow control devices studied include microtabs and microjets installed near the trailing-edge of the rotating blade. The divergent trailing-edge is also included in the study as a passive flow control device due to its practical interest. These trailing-edge devices are implemented on the fixed-pitch NREL Phase VI blade, using the original performance and flow characteristics as a benchmark. Both 2D and 3D simulations are carried out in order to investigate the suitability of the 2D blade sectional design analysis and control for the actual 3D rotating blades

Wind Turbine Blades Made of Functional Materials

Blades are designed to have good rigidity to be able to minimise the destruction that could be caused by rapid wind load and gust. The increase in length of the wind turbine contributes to the susceptibility of the wind turbine blade to the unpredictable destruction caused by random gusts. One of the ways to effectively increase the blade flexibility as well as increase its unloading effect led to the focus of this research on adaptive wind turbine blades. The project aims to investigate the potential benefits of flapping blades in the extraction of wind energy and proposing an analytical model for the prediction of the normalised induced twist with the sole purpose of having a robust tool for optimal design of adaptive wind turbine blades. In order to achieve these goals, the project is carried out in two aspects. Firstly, a proof of concept of a flapping blade; this report presents the preliminary results of the numerical simulation of a flapping-pitching rectangular flat plate in a uniform air flow. Various combinations of flapping amplitude, flapping frequency and pitching amplitude are analysed and their effect on the instantaneous and maximum lift coefficient is presented. The change in the flapping frequency and amplitude were shown to have considerable effect on the lift coefficient. It can be deduced from the results that the lift coefficient is influenced by the flapping frequency and flapping amplitude combination. The lift coefficient is most affected by the flapping amplitude when compared to the flapping frequency. The results indicate that the pitching amplitude initially enhances the lift coefficient. However, excessive pitching amplitude results in low lift coefficient. The second aspect is to develop a robust analytical model for the prediction of the normalised induced twist of an adaptive blade. Wind turbine adaptive blade design is a coupled aero-structure (CAS) design process, in which, the aerodynamic performance evaluation requires structural deformation analysis of the adaptive blade. However, employing finite element analysis (FEA) based commercial packages for the structural deformation analysis as part of the aerodynamic objective evaluation process has been proven to be time consuming. In order to develop the robust tool for the prediction of the normalised induced twist, the effect of shell thickness distributions, fibre angle distributions and materials are investigated using arbitrary lay-ups configurations. The structural/material configurations and the analyses of the adaptive blades are performed using an auxiliary software tool developed via MATLAB codes for implementing structural deformation analysis. The results are generated in ANSYS Parametric Design Language (APDL), which are read using ANSYS for the extraction of the results. Static and dynamic analyses are carried out for several cases, and the results are used to develop the analytical model for the prediction of the normalised induced twist. The proposed analytical model performance is validated by comparing the normalised induced twist predicted using the proposed model with those obtained using the ANSYS and the results suggest that the proposed model is efficient in predicting the normalised induced twist of an adaptive blade

Plasma Actuation for Active Control of Wind Turbine Power

Résumé Cette recherche évalue, optimise et démontre expérimentalement une nouvelle méthode pour réduire la portance et augmenter la traînée d’une pale de turbine éolienne pour contrôler la puissance éolienne à des vitesses de vent élevées. La méthode consiste à appliquer l’actionnement électro-fluidique du plasma pour accélérer la séparation de la couche limite sur les pales d’éolienne. L’effet de l’actionnement plasma sur un profil à deux dimensions d’éoliennes est d’abord évalué numériquement à de faibles nombres de Reynolds en utilisant un code commercial CFD auquel un modèle de l’actionneur plasma est intégré. Les résultats de ces simulations indiquent l’existence de conditions d’exploitation préférable pour l’actionneur plasma en termes de paramètres tel que sa force, la vitesse non-perturbée et sa position sens de la corde sur la pale. En ce qui concerne la force l’actionnement, il est constaté qu’il existe un seuil de la force au-delà duquel il y a un saut soudain dans la réduction de portance obtenue. Un bond semblable à l’effet d’actionnement est observé lorsque le nombre de Reynolds non-perturbé est réduit en deçà d’une certaine limite. L’existence de positions optimales pour l’actionneur plasma sur l’extrados de la pale est également observée. L’optimum est situé près du bord de fuite de l’aile pour les angles d’attaque avant le décrochage et il est déplacé en amont aux angles d’attaque près du décrochage et dépassés le décrochage. Toutes les simulations indiquent que la position de l’actionneur plasma par rapport au point de séparation de la couche limite est le facteur décisif à l’effet de l’actionneur sur la portance et la traînée. Ces simulations sont validées par des en soufflerie tests pour les mêmes conditions d’écoulement en soufflerie. Les mesures en soufflerie de la portance et la traînée se trouvent principalement à être cohérents avec les résultats de simulations. Le logiciel CFX validé expérimentalement est ensuite utilisé pour simuler l’écoulement à un Re réaliste pour les applications éoliennes. Cette étude montre que le niveau actuel de la force d’actionnement plasma est incapable d’exercer une influence perceptible sur les performances d’une éolienne. La théorie de l’élément de pale couplée à un bilan de quantité de mouvement est utilisée pour déterminer la quantité de la chute de portance qui serait nécessaire pour le fonctionnement à puissance nominale et cette exigence est comparée à l’impact de l’actuelle génération d’actionneurs plasma. Une tentative est faite pour estimer la force d’actionnement qui serait nécessaire pour réaliser la réduction de la puissance requise pour le fonctionnement nominal. Cette analyse montre qu’une force d’actionnement de deux ordres de grandeur serait nécessaire pour que le concept fonctionne sans l’aide d’un autre moyen de contrôle pour limiter la puissance des éoliennes.----------Abstract This research evaluates, optimizes and experimentally demonstrates a new method to reduce the lift and increase the drag of a wind turbine blade for controlling the turbine power at high wind speeds. The method consists of applying electro-fluidic plasma actuation to accelerate the separation of boundary layer on the wind turbine blade. The effect of plasma actuation on a two-dimensional wind turbine profile is first assessed numerically at low Reynolds numbers Re using a commercial CFD code to which a plasma actuator model is integrated. The results from these simulations indicate the existence of preferred operating conditions for the plasma actuator in terms of parameters such as its strength, the free-stream velocity and its chordwise position on the blade. With respect to the actuation strength, it is found that there exists a threshold strength beyond which there is a sudden jump in the lift reduction obtained. A similar jump in the actuation effect is observed when the free-stream Reynolds number is reduced past a certain limit. The existence of optimal positions for the actuator on the suction side of the blade is also observed. The optimum is situated near the airfoil’s trailing edge for a pre-stall angle of attack and it is displaced upstream at stall and post-stall angles of attack. All the simulations indicate that the position of the actuator relative to the point of separation of the boundary layer is the key element in the actuator’s effect on lift and drag. These simulations are validated by testing for the same flow conditions in wind tunnel. The wind tunnel measurements of lift and drag replicate the trends seen in the simulations. The experimentally validated CFD tool is then used to simulate wind turbine flows at a realistic Reynolds number. This study shows that the current level of plasma actuation strength is incapable of exerting any discernable influence on the performance of a wind turbine blade. The blade element momentum theory is used to determine the amount of lift drop that would be required for rated power operation and this requirement is compared with the impact of the current generation of plasma actuators. An attempt is made at estimating the actuation strength that would be necessary to bring about the power reduction required for rated operation. This analysis shows that actuator strength of two orders of magnitude higher would be required for the concept to work on its own to limit wind turbine power. This implies that it must be coupled with another method such as rotor speed control to have a realistic chance of application in the near future

Review of rotating wing dynamic stall: Experiments and flow control

Dynamic stall has been a technical challenge and a fluid dynamical subject of interest for more than fifty years; but in the last decade significant advances have been made in the understanding, prediction, modeling, and control of dynamic stall on rotors. This paper provides a summary of the state of the art of dynamic stall experiments and future directions in the understanding of dynamic stall on rotors. Experimental data sets are discussed, as well the direction of future research for control of dynamic stall. Coordinated testing between airfoils and rotating blades, as well as close integration between computational and experimental studies were found to be productive approaches. Advanced analysis methods, including statistical methods, modal representations, and artificial intelligence methods have led to significant advances in the understanding of dynamic stall. Investigations of dynamic stall control devices have allowed many useful targeted investigations of the transition to separated flow, but have not yet resulted in a commercially implemented device

Applied Aerodynamics

Aerodynamics, from a modern point of view, is a branch of physics that study physical laws and their applications, regarding the displacement of a body into a fluid, such concept could be applied to any body moving in a fluid at rest or any fluid moving around a body at rest. This Book covers a small part of the numerous cases of stationary and non stationary aerodynamics; wave generation and propagation; wind energy; flow control techniques and, also, sports aerodynamics. It's not an undergraduate text but is thought to be useful for those teachers and/or researchers which work in the several branches of applied aerodynamics and/or applied fluid dynamics, from experiments procedures to computational methods