The Experts below are selected from a list of 33741 Experts worldwide ranked by ideXlab platform
W.a.a.m. Bierbooms - One of the best experts on this subject based on the ideXlab platform.
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investigation of spatial Gusts with extreme rise time on the extreme loads of pitch regulated wind turbines
Wind Energy, 2005Co-Authors: W.a.a.m. BierboomsAbstract:It is assumed that the extreme loading of pitch-regulated turbines is caused by Gusts with an extreme rise time rather than an extreme gust amplitude. A special kind of wind field simulation, so-called constrained stochastic simulation, is dealt with in order to generate the desired Gusts. Just as in wind field simulation for fatigue purposes, it is assumed that turbulence is Gaussian; a possibility is mentioned of how to deal with non-Gaussian behaviour.On the basis of the presented theory it can be stated that the stochastic Gusts produced in this way are, in a statistical sense, not distinguishable from Gusts selected from a (very long) time series. An example of a spatial gust as well as the mean spatial gust shape is shown. For a reference turbine the maximum blade root flapping moment has been determined as a function of the gust centre in the rotor plane; the maximum response is obtained in the case where the gust hits one of the rotor blades at 75% of the radius. When the gust duration is large compared with the integral time constant of the controller, the controller can handle the gust as expected. However, even for small rise times it turns out that the maximum flap moment due to the gust is not significantly higher than that due to the background turbulence and 1P excitations. This may indicate that perhaps extreme rise time Gusts do not lead to extreme loading of pitch-regulated wind turbines. For a final judgement a proper probabilistic approach is necessary; an outline of such an approach has been sketched. Furthermore, it is recommended to do research on other gust types in order to find out the type which leads to the extreme wind turbine loading.Copyright © 2004 John Wiley & Sons, Ltd. WIND ENERGY Wind Energ. 2005; 8:17–34 (DOI: 10.1002/we.139)
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A Gust Model for Wind Turbine Design
Jsme International Journal Series B-fluids and Thermal Engineering, 2004Co-Authors: W.a.a.m. BierboomsAbstract:A new method, so called constrained stochastic simulation, has been developed in order to generate extreme gust time series, to be used to calculate the extreme loading of wind turbines. A constrained simulation corresponds to the addition, in a special manner, of turbulence and a deterministic part (which resembles the auto correlation function of turbulence). The stochastic Gusts produced in this way has been denoted NewGust and it is proved that they are, in a statistical sense, not distinguishable from Gusts selected from a (very long) stochastic time series, with the same amplitude. The NewGust method forms a part of on overall probabilistic method to determine the distribution of the wind turbine response on Gusts. This new probabilistic method enables wind turbine manufacturers to build more reliable and optimised wind turbines. The theoretical mean gust shape, as well as the probability of occurrence of Gusts, has been verified by measurements. In addition preliminary comparisons between numerical load simulations and wind turbine load measurements have been carried out.
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Extreme Gust Loading for Wind Turbines during Operation
Journal of Solar Energy Engineering-transactions of The Asme, 2001Co-Authors: Po Wen Cheng, W.a.a.m. BierboomsAbstract:One of the extreme load cases treated in the wind turbine certification is the extreme gust loading during operation. In the certification codes, it is treated in a deterministic way. A stochastic way of generating extreme Gusts that includes the turbulence properties of the wind is described in this paper. The stochastic Gusts are used to determine the extreme gust responses. The gust responses are processed together with the probability density of the gust amplitude and mean wind speed to obtain the gust response distribution. The distribution of the extreme gust response is determined. Different distribution types, namely Rayleigh, Weibull and Gumbel distributions, are applied to fit the distribution of the extreme gust responses. The reliability of the simulation results are analysed with statistical methods to determine the required number of simulations to obtain a reliable estimate of the statistical parameters of the distribution. The stochastic Gusts are applied to two example turbine models with different control concepts, a stall and a pitch-controll ed wind turbine. The results are compared to the gust response of the extreme operating gust specified in the EEC design standard. The results show that the extreme gust response can differ significantly depending on the control concept. The response of the deterministic gust proposed in the IEC is more conservative compared to the response of the stochastic gust.
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Distribution of extreme gust loads of wind turbines
Journal of Wind Engineering and Industrial Aerodynamics, 2001Co-Authors: Po Wen Cheng, W.a.a.m. BierboomsAbstract:Extreme gust loading of wind turbines has been treated deterministically as prescribed in the design codes, without taking into account the stochastic property of the wind turbulence. In this paper a rational approach to quantify the variability of the gust loading of a wind turbine is presented and a new approach on the simulation of the extreme Gusts with constrained simulations is proposed. The results from simulations with deterministic Gusts and stochastic Gusts are compared. The distribution of the extreme response due to extreme gust is derived using the constrained gust approach. The influence on response of a spatial gust and a point gust is studied. The effect of the gust centre on the turbine response has also been taken into account. The response distribution at a certain mean wind speed is determined with full-scale time domain simulation and compared to the distribution derived with constrained Gusts. The method is demonstrated using the turbine model of a prototype wind turbine; for this reason the result is preliminary and generalization should be made with care.
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Verification of the mean shape of extreme Gusts
Wind Energy, 1999Co-Authors: W.a.a.m. Bierbooms, Jan B. Dragt, Hans CleijneAbstract:For design load calculations for wind turbines it is necessary to determine the fatigue loads as well as the extreme loads. An advanced method has been presented previously to incorporate extreme turbulence Gusts in wind field simulation, the so-called ‘NewGust’ method. The gust generator works by constraining the random parameters of a stochastic wind field simulator. The present article deals with the verification of the mean shape of extreme Gusts. On the basis of a statistical analysis an expression of the mean gust shape is obtained. This theoretical gust shape is compared with the mean gust shape determined from both simulated and measured turbulence. The resemblance is remarkably good, which demonstrates the viability of the NewGust method. Copyright © 1999 John Wiley & Sons, Ltd.
Walt Musial - One of the best experts on this subject based on the ideXlab platform.
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Gusts and shear within hurricane eyewalls can exceed offshore wind turbine design standards
Geophysical Research Letters, 2017Co-Authors: Rochelle Worsnop, Julie K Lundquist, George H Bryan, Rick Damiani, Walt MusialAbstract:Offshore wind-energy development is underway in the U.S.A., with proposed sites located in hurricane-prone regions. Turbine-design criteria outlined by the International Electrotechnical Commission do not encompass the extreme wind speeds and directional shifts of hurricanes stronger than Category 2. We examine a hurricane's turbulent eyewall using large-eddy simulations with Cloud Model 1 (CM1). Gusts and mean wind speeds near the eyewall of a Category 5 hurricane exceed the current Class I turbine design threshold of 50 m s-1 mean wind and 70 m s-1 Gusts. Largest gust factors occur at the eye-eyewall interface. Further, shifts in wind direction suggest turbines must rotate or yaw faster than current practice. Although current design standards omit mention of wind direction change across the rotor layer, large values (15–50 deg) suggest that veer should be considered.
Julie K Lundquist - One of the best experts on this subject based on the ideXlab platform.
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Gusts and shear within hurricane eyewalls can exceed offshore wind turbine design standards
Geophysical Research Letters, 2017Co-Authors: Rochelle Worsnop, Julie K Lundquist, George H Bryan, Rick Damiani, Walt MusialAbstract:Offshore wind-energy development is underway in the U.S.A., with proposed sites located in hurricane-prone regions. Turbine-design criteria outlined by the International Electrotechnical Commission do not encompass the extreme wind speeds and directional shifts of hurricanes stronger than Category 2. We examine a hurricane's turbulent eyewall using large-eddy simulations with Cloud Model 1 (CM1). Gusts and mean wind speeds near the eyewall of a Category 5 hurricane exceed the current Class I turbine design threshold of 50 m s-1 mean wind and 70 m s-1 Gusts. Largest gust factors occur at the eye-eyewall interface. Further, shifts in wind direction suggest turbines must rotate or yaw faster than current practice. Although current design standards omit mention of wind direction change across the rotor layer, large values (15–50 deg) suggest that veer should be considered.
Sridhar Ravi - One of the best experts on this subject based on the ideXlab platform.
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bees with attitude the effects of directed Gusts on flight trajectories
Biology Open, 2018Co-Authors: Timothy Jakobi, Dmitry Kolomenskiy, Teruaki Ikeda, S Watkins, Alex Fisher, Hao Liu, Sridhar RaviAbstract:Flight is a complicated task at small scales in part due to the ubiquitous unsteady air which contains it. Flying organisms deal with these difficulties using active and passive control mechanisms to steer their body motion. Body attitudes of flapping organisms are linked with their resultant flight trajectories and performance, yet little is understood about how discrete unsteady aerodynamic phenomena affect the interlaced dynamics of such systems. In this study, we examined freely flying bumblebees subject to a single discrete gust to emulate aerodynamic disturbances encountered in nature. Bumblebees are expert commanders of the aerial domain as they persistently forage within complex terrain elements. By tracking the three-dimensional dynamics of bees flying through Gusts, we determined the sequences of motion that permit flight in three disturbance conditions: sideward, upward and downward Gusts. Bees executed a series of passive impulsive maneuvers followed by active recovery maneuvers. Impulsive motion was unique in each gust direction, maintaining control by passive manipulation of the body. Bees pitched up and slowed-down at the beginning of recovery in every disturbance, followed by corrective maneuvers which brought attitudes back to their original state. Bees were displaced the most by the sideward gust, displaying large lateral translations and roll deviations. Upward Gusts were easier for bees to fly through, causing only minor flight changes and minimal recovery times. Downward Gusts severely impaired the control response of bees, inflicting strong adverse forces which sharply upset trajectories. Bees used a variety of control strategies when flying in each disturbance, offering new insights into insect-scale flapping flight and bio-inspired robotic systems.
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bees with attitude the effect of Gusts on flight dynamics
arXiv: Fluid Dynamics, 2018Co-Authors: Timothy Jakobi, Dmitry Kolomenskiy, Teruaki Ikeda, Alex Fisher, Hao Liu, Simon C Watkins, Sridhar RaviAbstract:Flight is a complicated task at small scales in part due to the ubiquitous unsteady air which contains it. Flying organisms deal with these difficulties using active and passive control mechanisms to steer their body motion. Body attitudes of flapping organisms are linked with their resultant flight trajectories and performance, yet little is understood about how discrete unsteady aerodynamic phenomena affect the interlaced dynamics of such systems. In this study, we examined freely flying bumblebees subject to a single discrete gust to emulate aerodynamic disturbances encountered in nature. Bumblebees are expert commanders of the aerial domain as they persistently forage within complex terrain elements. Physical obstacles such as flowers produce local effects representative of a typified gust which threatens the precise control of intricate maneuvers. By tracking the 3D dynamics of bees flying through Gusts, we determined the sequences of motion that permit flight in three disturbance conditions. Bees repetitively executed a series of passive impulsive maneuvers followed by active recovery maneuvers. Impulsive motion was unique in each gust direction, maintaining control purely by passive manipulation of the body. Bees pitched up and slowed-down at the beginning of recovery in every disturbance, followed by corrective maneuvers which brought attitudes back to their original state. Bees were displaced the most by the sideward gust, displaying large lateral translations and roll deviations. Upward Gusts were easier for bees to fly through, causing only minor flight changes and minimal recovery times. Downward Gusts severely impaired the control response of bees, inflicting strong adverse forces which sharply upset trajectories. Bees used interesting control strategies when flying in each disturbance, offering new insights into insect-scale flapping flight and bio-inspired robotic systems.
Rochelle Worsnop - One of the best experts on this subject based on the ideXlab platform.
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Gusts and shear within hurricane eyewalls can exceed offshore wind turbine design standards
Geophysical Research Letters, 2017Co-Authors: Rochelle Worsnop, Julie K Lundquist, George H Bryan, Rick Damiani, Walt MusialAbstract:Offshore wind-energy development is underway in the U.S.A., with proposed sites located in hurricane-prone regions. Turbine-design criteria outlined by the International Electrotechnical Commission do not encompass the extreme wind speeds and directional shifts of hurricanes stronger than Category 2. We examine a hurricane's turbulent eyewall using large-eddy simulations with Cloud Model 1 (CM1). Gusts and mean wind speeds near the eyewall of a Category 5 hurricane exceed the current Class I turbine design threshold of 50 m s-1 mean wind and 70 m s-1 Gusts. Largest gust factors occur at the eye-eyewall interface. Further, shifts in wind direction suggest turbines must rotate or yaw faster than current practice. Although current design standards omit mention of wind direction change across the rotor layer, large values (15–50 deg) suggest that veer should be considered.