Insight into Rotational Effects on a Wind Turbine Blade Using Navier–Stokes Computations

Herráez, Iván; Stoevesandt, Bernhard; Peinke, Joachim

doi:10.3390/en7106798

Cited by 54 publications

(53 citation statements)

References 39 publications

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“…C l is increased by approximately 9 % as a consequence of the Himmelskamp effect, whereas C d does not seem to be influenced at all. This is also in agreement with our observations from the MEXICO turbine, where the Himmelskamp effect had a very limited influence on the drag (Herráez et al, 2014). Estimating the validity of the above described results for larger wind turbines is, however, not so straightforward.…”

Section: The Source Of the Spanwise Flowssupporting

confidence: 82%

“…As can be seen, the surface pressure does not present significant spanwise gradients. It is worth remarking that the same observation was made in the analysis of the MEXICO wind tunnel experiment (Herráez et al, 2014). Therefore, we conclude that the centrifugal force is the main source of spanwise flows.…”

Section: The Source Of the Spanwise Flowsmentioning

confidence: 56%

“…This effect delays the stall onset and enhances the lift force as compared to non-rotating blades operating at the same AoA. The Himmelskamp effect, also known as stall delay or rotational augmentation, has been studied by many authors both experimentally (Schreck and Robinson, 2002;Sicot et al, 2008;Ronsten, 1992) and numerically (Guntur and Sørensen, 2014;Herráez et al, 2014;Schreck et al, 2007), although it still remains far from being well understood and characterized. It mainly affects the blade root region and is known to be closely related to the existence of spanwise flows in the boundary layer.…”

Section: Spanwise Flows and Himmelskamp Effectmentioning

confidence: 99%

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Detailed analysis of the blade root flow of a horizontal axis wind turbine

et al. 2016

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Abstract. The root flow of wind turbine blades is subjected to complex physical mechanisms that influence significantly the rotor aerodynamic performance. Spanwise flows, the Himmelskamp effect, and the formation of the root vortex are examples of interrelated aerodynamic phenomena that take place in the blade root region. In this study we address those phenomena by means of particle image velocimetry (PIV) measurements and Reynolds-averaged Navier-Stokes (RANS) simulations. The numerical results obtained in this study are in very good agreement with the experiments and unveil the details of the intricate root flow. The Himmelskamp effect is shown to delay the stall onset and to enhance the lift force coefficient C l even at moderate angles of attack. This improvement in the aerodynamic performance occurs in spite of the negative influence of the mentioned effect on the suction peak of the involved blade sections. The results also show that the vortex emanating from the spanwise position of maximum chord length rotates in the opposite direction to the root vortex, which affects the wake evolution. Furthermore, the aerodynamic losses in the root region are demonstrated to take place much more gradually than at the tip.

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Section: The Source Of the Spanwise Flowssupporting

confidence: 82%

Section: The Source Of the Spanwise Flowsmentioning

confidence: 56%

Section: Spanwise Flows and Himmelskamp Effectmentioning

confidence: 99%

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Detailed analysis of the blade root flow of a horizontal axis wind turbine

et al. 2016

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“…The computations were conducted with OpenFOAM-2.3.0 [12], which is an open-source CFD code written in C++. The general validity of the code for wind turbine applications was shown by Herráez et al [13].…”

Section: Simulation Of Airfoil Aerodynamicsmentioning

confidence: 80%

The Influence of Eroded Blades on Wind Turbine Performance Using Numerical Simulations

et al. 2017

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During their operation, wind turbine blades are eroded due to rain and hail, or they are contaminated with insects. Since the relative inflow velocity is higher at the outer than at the inner part of the blades, erosion occurs mostly at the outer blade region. In order to prevent strong erosion, it is possible to install a leading edge protection, which can be applied to the blades after the initial installation, but changes the shape of the initial airfoil sections. It is unclear how this modification influences the aerodynamic performance of the turbine. Hence, it is investigated in this work. The NREL 5 MW turbine is simulated with clean and eroded blades, which are compared to coated blades equipped with leading edge protection. Aerodynamic polars are generated by means of Computational Fluid Dynamics, and load calculations are conducted using the blade element momentum theory. The analysis in this work shows that, compared to clean rotor blades, the worse aerodynamic behaviour of strongly eroded blades can lead to power losses of 9%. In contrast, coated blades only have a small impact on the turbine power of less than 1%.

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“…In particular, the flow at the root is a critical point. In fact, lift and drag coefficients of root airfoils of a rotating blade are affected by the so-called "stall delay" phenomenon (Himmelskamp, 1947;Guntur, 2011;Herráez, 2014); so the two-dimensional aerodynamic curves of these airfoils need to be adjusted at high angles of attack before being used in a BEM code like Wt_Perf to consider rotational effects. In this work, lift and drag coefficients of the inner airfoils (approximately from root to 20 % of the blade) have been extrapolated from a computational fluid dynamics (CFD) analysis of a rotating blade following the inverse BEM method reported in Guntu and Słrensen (2014), while two-dimensional aerodynamic coefficients obtained by using RFOIL have been used for the airfoils along the outer half of the blade, where rotational effects can be neglected (Tangler, 2005).…”

Section: Verification Of Wt_perf For Rotational Effectsmentioning

confidence: 99%

Design of advanced airfoil for stall-regulated wind turbines

Grasso¹,

Coiro²,

Bizzarrini³

et al. 2017

Wind Energ. Sci.

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Abstract. Nowadays, all the modern megawatt-class wind turbines make use of pitch control to optimise the rotor performance and control the turbine. However, for kilowatt-range machines, stall-regulated solutions are still attractive and largely used for their simplicity and robustness. In the design phase, the aerodynamics plays a crucial role, especially concerning the selection/design of the necessary airfoils. This is because the airfoil performance is supposed to guarantee high wind turbine performance but also the necessary machine control capabilities. In the present work, the design of a new airfoil dedicated to stall machines is discussed. The design strategy makes use of a numerical optimisation scheme, where a gradient-based algorithm is coupled with the RFOIL code and an original Bezier-curves-based parameterisation to describe the airfoil shape. The performances of the new airfoil are compared in free-and fixed-transition conditions. In addition, the performance of the rotor is analysed, comparing the impact of the new geometry with alternative candidates. The results show that the new airfoil offers better performance and control than existing candidates do.

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Insight into Rotational Effects on a Wind Turbine Blade Using Navier–Stokes Computations

Cited by 54 publications

References 39 publications

Detailed analysis of the blade root flow of a horizontal axis wind turbine

Detailed analysis of the blade root flow of a horizontal axis wind turbine

The Influence of Eroded Blades on Wind Turbine Performance Using Numerical Simulations

Design of advanced airfoil for stall-regulated wind turbines

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