The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Fotis Sotiropoulos - One of the best experts on this subject based on the ideXlab platform.
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Wake Statistics of Different-Scale Wind Turbines under Turbulent Boundary Layer Inflow
Energies, 2020Co-Authors: Xiaolei Yang, Daniel Foti, Christopher Lee Kelley, David Charles Maniaci, Fotis SotiropoulosAbstract:Subscale wind turbines can be installed in the field for the development of wind technologies, for which the blade aerodynamics can be designed in a way similar to that of a full-scale wind turbine. However, it is not clear whether the wake of a subscale turbine, which is located closer to the ground and faces different incoming turbulence, is also similar to that of a full-scale wind turbine. In this work we investigate the wakes from a full-scale wind turbine of Rotor Diameter 80 m and a subscale wind turbine of Rotor Diameter of 27 m using large-eddy simulation with the turbine blades and nacelle modeled using actuator surface models. The blade aerodynamics of the two turbines are the same. In the simulations, the two turbines also face the same turbulent boundary inflows. The computed results show differences between the two turbines for both velocity deficits and turbine-added turbulence kinetic energy. Such differences are further analyzed by examining the mean kinetic energy equation.
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Three-dimensional flow visualization in the wake of a miniature axial-flow hydrokinetic turbine
Experiments in Fluids, 2013Co-Authors: Leonardo P. Chamorro, Daniel R. Troolin, Seung-jae Lee, R. E. A. Arndt, Fotis SotiropoulosAbstract:Three-dimensional 3-component velocity measurements were made in the near wake region of a miniature 3-blade axial-flow turbine within a turbulent boundary layer. The model turbine was placed in an open channel flow and operated under subcritical conditions (Fr = 0.13). The spatial distribution of the basic flow statistics was obtained at various locations to render insights into the spatial features of the wake. Instantaneous and phase-averaged vortical structures were analyzed to get insights about their dynamics. The results showed a wake expansion proportional to the one-third power of the streamwise distance, within the first Rotor Diameter. Wake rotation was clearly identified up to a distance of roughly three Rotor Diameters. In particular, relatively high tangential velocity was observed near the wake core, but it was found to be nearly negligible at the turbine tip radius. In contrast, the radial velocity showed the opposite distribution, with higher radial velocity near the turbine tip and, due to symmetry, negligible at the Rotor axis. Larger turbulence intensity was found above the hub height and near the turbine tip. Strong coherent tip vortices, visualized in terms of the instantaneous vorticity and the λ _2 criterion, were observed within the first Rotor Diameter downstream of the turbine. These structures, influenced by the velocity gradient in the boundary layer, appeared to loose their stability at distances greater than two Rotor Diameters. Hub vortices were also identified. Measurements did not exhibit significant tip–hub vortex interaction within the first Rotor Diameter.
Wenlong Wu - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic effects of the ratio of Rotor Diameter to water depth: An experimental study
Renewable Energy, 2019Co-Authors: Yaling Chen, Wenlong WuAbstract:Abstract A series of flume experiments were carried out to investigate the influence of tidal turbine Rotor Diameter to depth ratio on the hydrodynamic process of wake flow using two different Diameter Rotor discs of the same porosity. Time-varying velocities were measured by an Acoustic Doppler Velocimeter at 8 cross-sections over the distance of 10 Diameters downstream, and the three-dimensional structures of wake flow and turbulence fields were obtained. Immediately downstream, the peak of velocity deficit occurred at the wake core and the value was greater for the large Diameter-depth ratio. Strong wake turbulence was mainly located in the shear stress layer around wake core. However, the attenuation processes of wake hydrodynamics were different under two Diameter-depth ratios. The momentum transfer was caused by Reynolds shear stress in both transverse and vertical directions. The vertical momentum transfer process was much more significant above the wake core than the lateral transfer process, but it decayed rapidly in near wake as the Diameter-depth ratio enlarged. The experimental results provide detailed data to better understand the wake propagation processes behind Rotor discs.
Hyung-joon Bang - One of the best experts on this subject based on the ideXlab platform.
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Active load control of wind turbine blade section with trailing edge flap: Wind tunnel testing:
Journal of Intelligent Material Systems and Structures, 2014Co-Authors: Jong-won Lee, Jae-hung Han, Hyung-ki Shin, Hyung-joon BangAbstract:In order to reduce the cost of energy, the Rotor Diameter of wind turbine has been continuously increased. Fatigue load becomes more important as wind turbines increase in size. The reduction of fa...
Mimi Hughes - One of the best experts on this subject based on the ideXlab platform.
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Sensitivity of southern California wind energy to turbine characteristics
Wind Energy, 2012Co-Authors: Scott B. Capps, Alex Hall, Mimi HughesAbstract:Using output from a high-resolution meteorological simulation, we evaluate the sensitivity of southern California wind energy generation to variations in key characteristics of current wind turbines. These characteristics include hub height, Rotor Diameter and rated power, and depend on turbine make and model. They shape the turbine's power curve and thus have large implications for the energy generation capacity of wind farms. For each characteristic, we find complex and substantial geographical variations in the sensitivity of energy generation. However, the sensitivity associated with each characteristic can be predicted by a single corresponding climate statistic, greatly simplifying understanding of the relationship between climate and turbine optimization for energy production. In the case of the sensitivity to Rotor Diameter, the change in energy output per unit change in Rotor Diameter at any location is directly proportional to the weighted average wind speed between the cut-in speed and the rated speed. The sensitivity to rated power variations is likewise captured by the percent of the wind speed distribution between the turbines rated and cut-out speeds. Finally, the sensitivity to hub height is proportional to lower atmospheric wind shear. Using a wind turbine component cost model, we also evaluate energy output increase per dollar investment in each turbine characteristic. We find that Rotor Diameter increases typically provide a much larger wind energy boost per dollar invested, although there are some zones where investment in the other two characteristics is competitive. Our study underscores the need for joint analysis of regional climate, turbine engineering and economic modeling to optimize wind energy production. Copyright © 2012 John Wiley & Sons, Ltd.
Yaling Chen - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic effects of the ratio of Rotor Diameter to water depth: An experimental study
Renewable Energy, 2019Co-Authors: Yaling Chen, Wenlong WuAbstract:Abstract A series of flume experiments were carried out to investigate the influence of tidal turbine Rotor Diameter to depth ratio on the hydrodynamic process of wake flow using two different Diameter Rotor discs of the same porosity. Time-varying velocities were measured by an Acoustic Doppler Velocimeter at 8 cross-sections over the distance of 10 Diameters downstream, and the three-dimensional structures of wake flow and turbulence fields were obtained. Immediately downstream, the peak of velocity deficit occurred at the wake core and the value was greater for the large Diameter-depth ratio. Strong wake turbulence was mainly located in the shear stress layer around wake core. However, the attenuation processes of wake hydrodynamics were different under two Diameter-depth ratios. The momentum transfer was caused by Reynolds shear stress in both transverse and vertical directions. The vertical momentum transfer process was much more significant above the wake core than the lateral transfer process, but it decayed rapidly in near wake as the Diameter-depth ratio enlarged. The experimental results provide detailed data to better understand the wake propagation processes behind Rotor discs.
