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Author: Publisher: ISBN: Category : Aerodynamic load Languages : en Pages : 0
Book Description
Dynamic loads must be predicted accurately in order to estimate the fatigue life of wind turbines operating in turbulent environments. Dynamic stall contributes to increased dynamic loads during normal operation of all types of horizontal-axis wind turbines (HAWTs). This reports illustrates how dynamic stall varies throughout the blade span of a 10 m HAWT during yawed and unyawed operatingconditions. Lift, drag, and pitching moment coefficients during dynamic stall are discussed. Resulting dynamic loads are presented, and the effects of dynamic stall on yaw loads are demonstrated using a yaw loads dynamic analysis (YAWDYN).
Author: Publisher: ISBN: Category : Aerodynamic load Languages : en Pages : 0
Book Description
Dynamic loads must be predicted accurately in order to estimate the fatigue life of wind turbines operating in turbulent environments. Dynamic stall contributes to increased dynamic loads during normal operation of all types of horizontal-axis wind turbines (HAWTs). This reports illustrates how dynamic stall varies throughout the blade span of a 10 m HAWT during yawed and unyawed operatingconditions. Lift, drag, and pitching moment coefficients during dynamic stall are discussed. Resulting dynamic loads are presented, and the effects of dynamic stall on yaw loads are demonstrated using a yaw loads dynamic analysis (YAWDYN).
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
It is well known that airfoils under unsteady flow conditions with a periodically varying angle of attack exhibit aerodynamic characteristics different from those under steady flow conditions, a phenomenon commonly known as dynamic stall. It is also well known that the steady aerodynamic characteristics of airfoils in the inboard region of a rotating blade differ from those under steady two-dimensional (2D) flow conditions, a phenomenon commonly known as rotational augmentation. This paper presents an investigation of these two phenomena together in the inboard parts of wind turbine blades. This analysis is carried out using data from three sources: (1) the National Renewable Energy Laboratory's Unsteady Aerodynamics Experiment Phase VI experimental data, including constant as well as continuously pitching blade conditions during axial operation, (2) data from unsteady Delayed Detached Eddy Simulations (DDES) carried out using the Technical University of Denmark's in-house flow solver Ellipsys3D, and (3) data from a simplified model based on the blade element momentum method with a dynamic stall subroutine that uses rotationally augmented steady-state polars obtained from steady Phase VI experimental sequences, instead of the traditional 2D nonrotating data.
Author: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
Surface pressure data from the National Renewable Energy Laboratory's ''Combined Experiment'' were analyzed to provide a statistical representation of dynamic stall occurrence on a downwind horizontal axis wind turbine (HAWT). Over twenty thousand blade rotational cycles were each characterized at four span locations by the maximum leading edge suction pressure and by the azimuth, velocity, and yaw at which it occurred. Peak suction values at least twice that seen in static wind tunnel tests were taken to be indicative of dynamic stall. The occurrence of dynamic stall at all but the inboard station (30% span) shows good quantitative agreement with the theoretical limits on inflow velocity and yaw that should yield dynamic stall. Two hypotheses were developed to explain the discrepancy at 30% span. Estimates are also given for the frequency of dynamic stall occurrence on upwind turbines. Operational regimes were identified which minimize the occurrence of dynamic stall events.
Author: J. G.Holierhoek Publisher: Elsevier Inc. Chapters ISBN: 0128089164 Category : Technology & Engineering Languages : en Pages : 30
Book Description
Aeroelasticity concerns the interaction between aerodynamics, dynamics and elasticity. This interaction can result in negatively or badly damped wind turbine blade modes, which can have a significant effect on the turbine lifetime. The first aeroelastic problem that occurred on commercial wind turbines concerned a negatively damped edgewise mode. It is important to ensure that there is some out-of-plane deformation in this mode shape to prevent the instability. For larger turbine blades with lower torsional stiffness and the possibility of higher tip speeds for the offshore designs, classical flutter could also become relevant. When designing a wind turbine blade, it is therefore crucial that there is enough damping for the different modes and that there is no coincidence of natural frequencies with excitation frequencies (resonance). An effective aeroelastic analysis is also important, and the tools used for such an analysis must include the necessary detail in the structural model.
Author: Martin O. L. Hansen Publisher: Routledge ISBN: 1136572260 Category : Technology & Engineering Languages : en Pages : 192
Book Description
Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its second edition, it has been entirely updated and substantially extended to reflect advances in technology, research into rotor aerodynamics and the structural response of the wind turbine structure. Topics covered include increasing mass flow through the turbine, performance at low and high wind speeds, assessment of the extreme conditions under which the turbine will perform and the theory for calculating the lifetime of the turbine. The classical Blade Element Momentum method is also covered, as are eigenmodes and the dynamic behaviour of a turbine. The new material includes a description of the effects of the dynamics and how this can be modelled in an ?aeroelastic code?, which is widely used in the design and verification of modern wind turbines. Further, the description of how to calculate the vibration of the whole construction, as well as the time varying loads, has been substantially updated.
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Author: Charles P. Butterfield
Author: Charles P. Butterfield
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Author: Derek E. Shipley
Author: Hanns Friedrich Muller-Vahl
Author: Charles P. Butterfield
Author: J. G.Holierhoek
Author: Martin O. L. Hansen