The Comparison of Form Drag and Profile Drag of a Wind Turbine Blade Section in Pitching
Extensive wind tunnel tests have been conducted to investigate the unsteady flow field over and behind a 2D model of a 660 kW wind turbine blade section in pitching motion. The surface pressure and wake dynamic pressure variation at a distance of 1.5 chord length from trailing edge were measured by pressure transducers during several oscillating cycles at 3 reduced frequencies and oscillating amplitudes. Moreover, form drag and linear momentum deficit are extracted and compared at various conditions. The results show that the wake velocity field and surface pressure of the model have similar behavior before and after the airfoil beyond the static stall angle of attack. In addition, the effects of reduced frequency and oscillation amplitudes are discussed. Keywords—Pitching motion, form drag, Profile drag, wind turbine.
Challenges in Modeling the Unsteady Aerodynamics of Wind Turbines
Many of the aerodynamic phenomena contributing to the observed effects on wind turbines are now known, but the details of the flow are still poorly understood and are challenging to predict accurately, issues discussed herein include the modeling of the induced velocity field produced by the vortical wake behind the turbine, the various unsteady aerodynamic issues associated with the blade sections, and the intricacies of dynamic stall. Fundamental limits exist in the capabilities of all models, and misunderstandings or ambiguities can also arise in how these models should be properly applied. A challenge for analysts is to use complementary experimental measurements and modeling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application.Copyright © 2002 by J. G. Leishman and ASME
Introduction to Dutch Law for Foreign Lawyers
Part 1 Dutch legal system: history sources judicial organization legal education and the legal profession classification. Part 2 Private law: family law property law law of obligations representation and procuration legal persons law of succession commercial law air law civil procedure private international law. Part 3 Public law: constitutional law administrative law criminal justice system tax law economic law. Part 4 Labour law. Part 5 Legal philosophy.