Rotationally Augmented Flow Structures and Time Varying Loads on Turbine Blades

Schreck, S.

doi:10.2514/6.2007-627

Cited by 11 publications

(5 citation statements)

References 29 publications

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“…[50] UAE C n standard deviation behaviors seen in Figure 6 for 0.30R are representative of those at 0.47R, 0.63R, and 0.80R. [51] At all four radial locations for the rotating blade, U ∞ values below 9 or 10 m/s were accompanied by attenuated C n standard deviation levels, which remained well below C n standard deviation levels predicted for 5 percent inflow turbulence intensity. However, modest increases in U ∞ elicited a rapid and substantial rise in UAE C n standard deviation, which peaked in the range 15 ≤ U ∞ ≤ 20 m/s.…”

Section: Axisymmetric C N Unsteadiness Amplificationmentioning

confidence: 61%

“…Recent research has shown that C n standard deviation levels correlate with the chord length enveloped by the shear layer. [51] The image shown in Figure 7 is a two-dimensional section extracted from a strongly three-dimensional flow field. To gain an appreciation for the complex three-dimensional character, Figure 8 shows computed surface limiting streamlines on the suction surface of the UAE blade, for U ∞ = 15 m/s.…”

Section: Courtesy Of N Sørensen Risø National Laboratorymentioning

confidence: 99%

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Wind Turbine Blade Flow Fields and Prospects for Active Aerodynamic Control

Schreck

Robinson

2007

Volume 2: Fora, Parts a and B

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As wind turbines continue to grow larger, problems associated with adverse aerodynamic loads will grow more critical. Thus, the wind energy technical community has begun to seriously consider the potential of aerodynamic control methodologies for mitigating adverse aerodynamic loading. Spatial and temporal attributes of the structures and processes present in these flow fields hold important implications for active aerodynamic control methodologies currently being contemplated for wind turbine applications. The current work uses complementary experimental and computational methodologies, to isolate and characterize key attributes of blade flow fields associated with axisymmetric and yawed turbine operation. During axisymmetric operation, a highly three-dimensional, shear layer dominated flow field yields rotational augmentation of both mean and standard deviation levels of aerodynamic forces. Under yawed operating conditions, pseudo-sinusoidal inflow angle oscillations elicit dynamic stall, which significantly intensifies aerodynamic load production. Both rotationally augmented and dynamically stalled flows possess attributes likely to pose central challenges for turbine flow control. Whether active control of turbine aerodynamics can help alleviate adverse aerodynamic loads will depend on comprehension and command of the issues documented herein.

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Section: Axisymmetric C N Unsteadiness Amplificationmentioning

confidence: 61%

Section: Courtesy Of N Sørensen Risø National Laboratorymentioning

confidence: 99%

Wind Turbine Blade Flow Fields and Prospects for Active Aerodynamic Control

Schreck

Robinson

2007

Volume 2: Fora, Parts a and B

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“…This results in massive aerodynamic loading of the slender and compliant blades, mainly in blade flapwise direction depending on the local wind vector (cf., Wind ). Local aerodynamics in the rotating system are complex and rotational lift enhancement and stall delay can play important roles . Mainly due to unsteady inflow, dynamic stall effects, that is, flow separation and reattachment behavior differing from the quasistatic phenomena, may lead to significantly changing blade loads.…”

Section: System Properties Of Offshore Wind Turbines and Resulting Loadsmentioning

confidence: 99%

Offshore wind turbine environment, loads, simulation, and design

Vorpahl

Schwarze

Fischer

et al. 2012

WIREs Energy & Environment

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In the design, certification, and optimization of offshore wind turbines, extensive loads simulation is inevitable to develop reliable and cost-effective turbines. Description of the marine environment is based on a variety of techniques taking the stochastic nature of both, the wind and the water waves into account. The wind turbine is a highly dynamic system including effects of heavy rotating machinery and other significant nonlinearities leading to static, cyclic, transient, and stochastic loads. Due to the nature of the external loading, the system properties and the turbine design lifetime, offshore wind turbines are prone to fatigue-driven failure. For loads assessment, aero-hydro-servo-elastic tools are used including the coupled effects of the environment and the turbine to simulate the overall lifetime of the turbine in the harsh marine environment. These tools are constantly further developed and adapted to the needs of a fast-growing industry and newly arisi ng turbine concepts. Engineering approaches to allow for certification and reliable design are summarized in extensive guidelines and standards supporting engineers in daily design work

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“…A study conducted by Schreck (2007) showed how blade pressure measurements were performed using blade surface pressure taps and transducers mounted on the inside of a large HAWT. Since, these blades are large (compared to axial fans), enough space in the blade cavity was available to encapsulate the pressure transducers and other measuring equipment.…”

Section: Experimental Analysesmentioning

confidence: 99%

Investigation of the Flow Field in the Vicinity of an Axial Flow Fan During Low Flow Rates

Louw

Backström

Spuy

2014

Volume 1A: Aircraft Engine; Fans and Blowers

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Large axial flow fans are used in forced draft air cooled heat exchangers (ACHEs). Previous studies have shown that adverse operating conditions cause certain sectors of the fan, or the fan as a whole to operate at very low flow rates, thereby reducing the cooling effectiveness of the ACHE. The present study is directed towards the experimental and numerical analyses of the flow in the vicinity of an axial flow fan during low flow rates. This is done to obtain the global flow structure up and downstream of the fan. A near-free-vortex fan, designed for specific application in ACHEs, is used for the investigation. Experimental fan testing was conducted in a British Standard 848, type A fan test facility, to obtain the fan characteristic. Both steady-state and time-dependent numerical simulations were performed, depending on the operating condition of the fan, using the Realizable k-ε turbulence model. Good agreement is found between the numerically and experimentally obtained fan characteristic data. Using data from the numerical simulations, the time and circumferentially averaged flow field is presented. At the design flow rate the downstream fan jet mainly moves in the axial and tangential direction, as expected for a free-vortex design criteria, with a small amount of radial flow that can be observed. As the flow rate through the fan is decreased, it is evident that the down-stream fan jet gradually shifts more diagonally outwards, and the region where reverse flow occur between the fan jet and the fan rotational axis increases. At very low flow rates the flow close to the tip reverses through the fan, producing a small recirculation zone as well as swirl at certain locations upstream of the fan.

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Rotationally Augmented Flow Structures and Time Varying Loads on Turbine Blades

Cited by 11 publications

References 29 publications

Wind Turbine Blade Flow Fields and Prospects for Active Aerodynamic Control

Wind Turbine Blade Flow Fields and Prospects for Active Aerodynamic Control

Offshore wind turbine environment, loads, simulation, and design

Investigation of the Flow Field in the Vicinity of an Axial Flow Fan During Low Flow Rates

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