4 research outputs found
Inertial and aerodynamic tuning of passive devices for load alleviation on wind turbines
This paper describes tuning concepts for passive devices aimed at load alleviation in wind turbines. Two types of tuning are considered: inertial and aerodynamic. The first concept is illustrated with reference to a passive flap, while the second with reference to a passive tip. In both cases, the goal is to reduce loads with devices that are as simple as possible, and do not require sensors nor actuators. The main features and critical issues of each concept are highlighted and illustrated with reference to a large conceptual 10 MW wind turbine
Cheating, inequality aversion, and appealing to social norms
We conduct a field experiment involving 143, 9-years old children in their classrooms. Children are requested to flip a coin in private and receive a big or a small prize depending on the outcome they report. Comparing the actual and theoretical distribution of reported wins, we find evidence of cheating at the aggregate level. By using behavioral data gathered on previous and subsequent meetings with the same children, we are able to explore the relationship between cheating behavior, other regarding preferences, and the tendency to appeal to social norms in judging unfair behaviors. Children who are classified as concerned about inequality are less likely to cheat. Similarly, children who are more likely to appeal to social norms in judging unfair behaviors are also less likely to cheat. We find no significant relationship between inequality concern and social norms sensitivity, suggesting that these mechanisms work differently interacting with children moral behavior
Ultimate and fatigue load mitigation by an inertial-driven passive flap, using a geometrically exact multibody formulation
The paper characterizes the performance of a passive flap concept when applied to a modern very large conceptual wind turbine. The passive flap responds automatically to blade and/or tower vibrations, inducing a change of camber that opposes dynamic loads on the wind turbine. This is obtained in a purely passive manner, without the need for actuators or sensors. The present study is based on a detailed, geometrically exact multibody formulation of the device, which is able to capture all kinematic and structural dynamic effects of this inertia-driven device. The present modeling of the passive device improves on previous studies conducted with simplified models. Results show a significant ability in the reduction of both fatigue and ultimate loads, including the case of flap-specific fault scenarios. Solutions for limiting losses in energy yield caused by non-null average flap rotations in the partial load region are also investigated. The present analysis motivates further studies aimed at reaping the benefits of load alleviation enabled by the passive flap, for example by designing a new enlarged rotor at similar key loads on the rest of the machine