Inboard Stall Delay due to Rotation

Dumitrescu, Horia; Cardoş, Vladimir

doi:10.2514/1.c031329

Cited by 17 publications

(15 citation statements)

References 21 publications

(15 reference statements)

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“…In the post-stall regime -at least up to 15 m/s, the turbine torque is good evaluated, whereas the blade bending moment closes into the experimental data. For wind speed V w > 15 m/s, vortex horn stretching structure conducts to increase of turbine torque and root flap bending moment in excellent agreement with experimental data and Dumitrescu-Cardos's prediction method [1,3].…”

Section: Numerical Simulation Of the Nrel Phase VI Rotorsupporting

confidence: 73%

“…This behaviour is visible from the streamlines over the blade surface during operation in deep stall [1].…”

Section: Introductionmentioning

confidence: 91%

“…The transfer of angular (kinetic) moment to first half of blade (conservation of angular kinetic moment) implies appearance of vortex horn at V w = 11 m/s (figure 1.b) [1]. With increasing the wind speed, the vortex horn stretches and for V w > 17 m/s vortex horn has a stable spatial topology.…”

Section: Numerical Simulation Of the Nrel Phase VI Rotormentioning

confidence: 98%

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An Investigation of the Separate Flow and Stall‐delay for Horizontal‐Axis Wind Turbine

Frunzulică

Mahu

Dumitrescu

2012

Proc Appl Math and Mech

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The flow characteristics and stall delay phenomenon of a stall regulated wind turbine rotor due to blade rotation in steady state non-yawed conditions are investigated. An incompressible Reynolds-averaged Navier-Stokes solver is applied to carry out the separate flow cases at high wind speeds from 11 m/s to 25 m/s with an interval of 2 m/s. The objective of the present research effort is to validate a first-principles based approach for modeling horizontal axis wind turbines (HAWT) under stalled flow conditions using NREL/ Phase VI rotor data. The computational results are compared with the predicted values derived by a new stall-delay model and blade element momentum (BEM) method.

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Section: Numerical Simulation Of the Nrel Phase VI Rotorsupporting

confidence: 73%

“…This behaviour is visible from the streamlines over the blade surface during operation in deep stall [1].…”

Section: Introductionmentioning

confidence: 91%

See 1 more Smart Citation

An Investigation of the Separate Flow and Stall‐delay for Horizontal‐Axis Wind Turbine

Frunzulică

Mahu

Dumitrescu

2012

Proc Appl Math and Mech

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“…Stage 1 represents the delay in the onset of separation in response to reduction in adverse pressure gradients produced by the influence of the strong vortex wake at the root. The phenomenon is initiated at TSR = 3.0, where the suction pressure equalizes to the kinetic energy of wake ( Fig.1.a) resulting mainly in boundary layer reattaching and the rise of a leading-edge separation bubble, a stable focus as topological entity [1].…”

Section: Delayed Stall Events On a Wind Turbine Bladementioning

confidence: 99%

“…The phenomenon of stall-delay can be described as a three step process [1]: rise of strong wake by clustering of vortices shed from the inboard mid-span sections at TSR = 3.0 (TSR = tip-speed ratio), inviscid load (pressure) redistribution along the airfoil chord, at the constant circulation (C L,IN V ) of the start regime (TSR = 3) for increased suction pressure when TSR < 3.0, followed by spanwise circulation (or lift) decay involving the stretching of separation bubble surface all the way to the trailing edge for increasing radius; beyond that blade section (r/R = (T SR) −1 ) the flow is separated over the whole airfoil and the leading-edge stall occurs.…”

Section: Introductionmentioning

confidence: 99%

An insight into the rotational stall delay

Dumitrescu¹,

Cardoş²,

Frunzulică³

2012

Proc Appl Math and Mech

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Blade element momentum (BEM) theory which is based on the two-dimensional (2D) aerodynamic properties of airfoil blade element is the most common computational engineering method for the prediction of loads and power curves of wind turbines. Although most BEM models yield acceptable results for high tip-speed ratios where the local angles of attack are small, no generally accepted model exists up to date that consistently predicts the loads and power in stall regime for stallcontrolled turbines. Understanding of the stall delay phenomenon on wind turbines remains, to this day, incomplete. The lack of a conceptual model for the complex three-dimensional (3D) flow field on the rotor blade, where stall is begins, how it progresses and where stall is practically terminated, has hindered the finding of a unanimously accepted solution. The paper aims at giving a better understanding of the delayed stall events and a reasonably simple correction model that complements the 2D airfoil characteristics used to a BEM method.

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Robustness of the Leading Edge Vortex on Rotating Wings to Unsteady Perturbations

Jardin

2022

Flow Turbulence Combust

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The vast majority of research works on low aspect ratio rotating wings report that, at high angle of attack, the leading edge vortex that forms on the upper surface of the wing is stable. This 'trick' is used by insects and auto-rotating seeds, for example, to achieve the desirable amount of lift. Yet, a few experimental studies suggest that leading edge vortices might be unstable under similar, low Rossby number, conditions. While it is unclear what causes vortex shedding in these studies, the present communication explores the sensitivity of leading edge vortex attachment to perturbations of the rotating speed and demonstrates that shedding can be triggered even for very small perturbations, corresponding to wing tip displacements lower than 1% of the wing chord.

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Inboard Stall Delay due to Rotation

Cited by 17 publications

References 21 publications

An Investigation of the Separate Flow and Stall‐delay for Horizontal‐Axis Wind Turbine

An Investigation of the Separate Flow and Stall‐delay for Horizontal‐Axis Wind Turbine

An insight into the rotational stall delay

Robustness of the Leading Edge Vortex on Rotating Wings to Unsteady Perturbations

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