High-lift systems have a major influence on the sizing, economics, and safety of most transport airplane configurations. The combination of complexity in flow physics, geometry, and system support and actuation has historically led to a lengthy and experiment intensive development process. However, during the recent past engineering design has changed significantly as a result of rapid developments in computational hardware and software. In aerodynamic design, computational methods are slowly superseding empirical methods and design engineers are spending more and more time applying computational tools instead of conducting physical experiments to design and analyze aircraft including their high-lift systems. The purpose of this paper is to review recent developments in aerodynamic design and analysis methods for multi-element high-lift systems on transport airplanes. Attention is also paid to the associated mechanical and cost problems since a multi-element high-lift system must be as simple and economical as possible while meeting the required aerodynamic performance levels. r

This paper outlines the benefi ts and challenges of utilizing active fl ow control (AFC) for wind turbines. The goal of AFC is to mitigate damaging loads and control the aeroelastic response of wind turbine blades. This can be accomplished by sensing changes in turbine operation and activating devices to adjust the sectional lift coeffi cient and/or local angle of attack. Fifteen AFC devices are introduced, and four are described in more detail. Non-traditional trailing-edge fl aps, plasma actuators, vortex generator jets and microtabs are examples of devices that hold promise for wind turbine control. The microtab system is discussed in further detail including recent experimental results demonstrating its effectiveness in a three-dimensional environment. Wind tunnel tests indicated that a nearly constant change in C L over a wide range of angles of attack is possible with microtab control. Using an angle of attack of 5 degrees as a reference, microtabs with a height of 1.5%c were capable of increasing CL by +0.21 (37%) and decreasing CL by −0.23 (−40%). The results are consistent with fi ndings from past two-dimensional experiments and numerical efforts. Through comparisons to other load control studies, the controllable range of this micro-tab system is determined to be suitable for smart blade applications.Equation (1) illustrates that there are several distinct approaches that can be taken to lower the COE. One way is to make more reliable turbines, thereby reducing the downtime and O&M costs. Another is to reduce the amount of materials or improve manufacturing techniques to decrease capital cost. COE can also be reduced by increasing the rotor diameter and turbine size; this has been occurring since the beginning of the commercial wind industry. A larger turbine can capture more energy throughout its lifetime, and although the cost of the turbine will increase and O&M may increase as well, the COE has been declining.Signifi cant growth of wind turbine size and weight over the past few decades has made it impossible to control turbines passively as they were controlled in the past. Modern turbines rely on sophisticated control systems that assure safe and optimal operation under a variety of atmospheric conditions. As turbines grow in size, the structural and fatigue loads become more pronounced. Implementing new and innovative load control techniques could decrease RESEARCH ARTICLE Wind Energ. 2010; 13:239-253

The adoption of blunt trailing edge airfoils for the inboard region of large wind turbine blades has been proposed. Blunt trailing edge airfoils would not only provide a number of structural benefits, such as increased structural volume and ease of fabrication and handling, but they have also been found to improve the lift characteristics of airfoils. Therefore, the incorporation of blunt trailing edge airfoils would allow blade designers to more freely address the structural demands without having to sacrifice aerodynamic performance. Limited experimental data make it difficult for wind turbine designers to consider and conduct tradeoff studies using these section shapes and has provided the impetus for the present analysis of blunt trailing edge airfoils using computational fluid dynamics. Several computational techniques are applied, including a viscous/inviscid interaction method and three Reynolds-averaged Navier-Stokes methods.

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A preliminary design study of an advanced 50 m blade for utility wind turbines is presented and discussed. The effort was part of the Department of Energy WindPACT Blade System Design Study with the goal to investigate and evaluate design and manufacturing issues for wind turbine blades in the 1–10 MW size range. Two different blade designs are considered and compared in this article. The first is a fibreglass design, while the second design selectively incorporates carbon fibre in the main structural elements. The addition of carbon results in modest cost increases and provides significant benefits, particularly with respect to blade deflection. The structural efficiency of both designs was maximized by tailoring the thickness of the blade cross‐sections to simplify the construction of the internal members. Inboard the blades incorporate thick blunt trailing edge aerofoils (flatback aerofoils), while outboard more conventional sharp trailing edge high‐lift aerofoils are used. The outboard section chord lengths were adjusted to yield the least complex and costly internal blade structure. A significant portion of blade weight is related to the root buildup and metal hardware for typical root attachment designs. The results show that increasing the number of studs has a positive effect on total weight, because it reduces the required root laminate thickness. The aerodynamic performance of the blade aerofoils was predicted using computational techniques that properly simulate blunt trailing edge flows. The performance of the rotor was predicted assuming both clean and soiled blade surface conditions. The rotor is shown to provide excellent performance at a weight significantly lower than that of current rotors of this size. Copyright © 2004 John Wiley & Sons, Ltd.