Rotational Effects on the Boundary-Layer Flow in Wind Turbines

Dumitrescu, Horia; Cardoş, Vladimir

doi:10.2514/1.9103

Cited by 59 publications

(36 citation statements)

References 5 publications

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“…Having those results in mind, the choice of the k-ω SST turbulence model for the three-dimensional (3D) simulations becomes obvious. This choice is also supported by the recommendations of many authors [17,25].…”

Section: D Simulationsupporting

confidence: 50%

“…This state is characterized by maintaining significant lift coefficient that is comparable with the 2D airfoil data measured in the wind tunnel with the occurrence of flow separation for the airfoil at a higher angle of attack beyond the stalled angle [17]. Even though this phenomenon was first observed in propeller blades [18], it has been applied to helicopters and we have even used our knowledge of this phenomenon (stall delay model) in wind turbine fields [2,6].…”

Section: Improved Bem Methodsmentioning

confidence: 93%

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The Performance Test of Three Different Horizontal Axis Wind Turbine (HAWT) Blade Shapes Using Experimental and Numerical Methods

2013

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Three different horizontal axis wind turbine (HAWT) blade geometries with the same diameter of 0.72 m using the same NACA4418 airfoil profile have been investigated both experimentally and numerically. The first is an optimum (OPT) blade shape, obtained using improved blade element momentum (BEM) theory. A detailed description of the blade geometry is also given. The second is an untapered and optimum twist (UOT) blade with the same twist distributions as the OPT blade. The third blade is untapered and untwisted (UUT). Wind tunnel experiments were used to measure the power coefficients of these blades, and the results indicate that both the OPT and UOT blades perform with the same maximum power coefficient, C p = 0.428, but it is located at different tip speed ratio, λ = 4.92 for the OPT blade and λ = 4.32 for the UOT blade. The UUT blade has a maximum power coefficient of C p = 0.210 at λ = 3.86. After the tests, numerical simulations were performed using a full three-dimensional computational fluid dynamics (CFD) method using the k-ω SST turbulence model. It has been found that CFD predictions reproduce the most accurate model power coefficients. The good agreement between the measured and computed power coefficients of the three models strongly OPEN ACCESSEnergies 2013, 6 2785 suggest that accurate predictions of HAWT blade performance at full-scale conditions are also possible using the CFD method.

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Section: D Simulationsupporting

confidence: 50%

Section: Improved Bem Methodsmentioning

confidence: 93%

The Performance Test of Three Different Horizontal Axis Wind Turbine (HAWT) Blade Shapes Using Experimental and Numerical Methods

2013

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“…5 Moreover, some researches indicated the importance of blade geometry coupled with blade rotation for stall delay. 6 This may also be supported by the other observations 7,8,9 showed an apparent stall delay phenomenon at the inner part of the blade where high angles of attack occur.…”

Section: A Backgroundsupporting

confidence: 77%

Experimental and Numerical Quantification of Radial Flow in the Root Region of a HAWT Blade

Akay

Ferreira

Bussel

et al. 2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…In fact, Ekman-like boundary layer profiles have been calculated for wind turbine blades (Dumitrescu and Cardos, 2003). Important historic evidence for spanwise flow on a propeller at low Ro can be found in Himmelskamp (Himmelskamp, 1947), a classic reference in wind turbine literature.…”

Section: Lentink and M H Dickinsonmentioning

confidence: 99%

Rotational accelerations stabilize leading edge vortices on revolving fly wings

Lentink

Dickinson

2009

Journal of Experimental Biology

463

474

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SUMMARYThe aerodynamic performance of hovering insects is largely explained by the presence of a stably attached leading edge vortex (LEV) on top of their wings. Although LEVs have been visualized on real, physically modeled, and simulated insects, the physical mechanisms responsible for their stability are poorly understood. To gain fundamental insight into LEV stability on flapping fly wings we expressed the Navier-Stokes equations in a rotating frame of reference attached to the wing's surface. Using these equations we show that LEV dynamics on flapping wings are governed by three terms: angular, centripetal and Coriolis acceleration. Our analysis for hovering conditions shows that angular acceleration is proportional to the inverse of dimensionless stroke amplitude, whereas Coriolis and centripetal acceleration are proportional to the inverse of the Rossby number. Using a dynamically scaled robot model of a flapping fruit fly wing to systematically vary these dimensionless numbers, we determined which of the three accelerations mediate LEV stability. Our force measurements and flow visualizations indicate that the LEV is stabilized by the 'quasi-steady' centripetal and Coriolis accelerations that are present at low Rossby number and result from the propeller-like sweep of the wing. In contrast, the unsteady angular acceleration that results from the back and forth motion of a flapping wing does not appear to play a role in the stable attachment of the LEV. Angular acceleration is, however, critical for LEV integrity as we found it can mediate LEV spiral bursting, a high Reynolds number effect. Our analysis and experiments further suggest that the mechanism responsible for LEV stability is not dependent on Reynolds number, at least over the range most relevant for insect flight (100

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Rotational Effects on the Boundary-Layer Flow in Wind Turbines

Cited by 59 publications

References 5 publications

The Performance Test of Three Different Horizontal Axis Wind Turbine (HAWT) Blade Shapes Using Experimental and Numerical Methods

The Performance Test of Three Different Horizontal Axis Wind Turbine (HAWT) Blade Shapes Using Experimental and Numerical Methods

Experimental and Numerical Quantification of Radial Flow in the Root Region of a HAWT Blade

Rotational accelerations stabilize leading edge vortices on revolving fly wings

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