The origins of a wind turbine tip vortex

Micallef, Daniel; Akay, B.; Ferreira, Carlos; Sant, Tonio; Bussel, Gerard van

doi:10.1088/1742-6596/555/1/012074

Cited by 21 publications

(17 citation statements)

References 1 publication

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“…The same article also shows that full blade Reynolds-averaged NavierStokes (RANS) simulations as well as panel code computations allow a much more realistic study of the tip vortex formation mechanism. Indeed, the use of a panel code allowed Micallef et al (2012) to study the origin of the tip vortex on a wind tunnel model rotor, unveiling the complex distribution of bound vorticity at the blade tip. However, to the best of our knowledge, the formation of the root vortex has not been addressed until now.…”

Section: The Root Vortexmentioning

confidence: 99%

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 Root Vortexmentioning

confidence: 99%

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

et al. 2016

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“…First is an exact solution of Wu's equation, to be discussed in § 3.4, where a radial component of the disc load is present when the disc has thickness. Second, analyses of several wind tunnel experiments (Xiao et al 2011;Micallef 2012;Micallef et al 2012) have shown details of the flow field very close to the tips of model wind turbine rotor blades for which only radial pressure gradients or loads at the blade tip provide an explanation: after being released by the blade tip, the tip vortex first moves inboard before the wake expansion drives it outboard. The inboard motion leads one to expect a similar radial load.…”

Section: Brief History Of Rotor Aerodynamicsmentioning

confidence: 99%

“…The flow near the blade tip of these rotors shows the tip vortex, when leaving the tip, moving inboard after which the wake expansion moves the vortex to a larger radius Micallef et al (2013). provide a detailed description of this phenomenon,Micallef (2012) andMicallef et al (2012) give the experimental data of the TUD and Mexico rotor experiments and the analyses, asXiao et al (2011) does for the NREL model rotor. The first mention of this effect was by van Kuik…”

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confidence: 99%

The role of conservative forces in rotor aerodynamics

et al. 2014

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The theory to predict the performance and loads on rotors (propellers, screws,\ud windmills) has a history of more than a century. Apart from modern computational\ud fluid dynamics and vortex panel models taking the true blade geometry into account,\ud most other models proceed from an infinitely thin actuator disc or line. These models\ud assume an externally defined force field distributed at the disc or line, representing\ud the loads on the real rotor. Given this force field, the flow is solved by momentum\ud balances or by the equations of motion. The use of external force fields was discussed\ud in textbooks of the first decades of the 20th century, but has received little attention\ud since then. This paper investigates the higher-order effect of adding thickness to the\ud actuator disc or changing the actuator line to a blade with cross-sectional dimensions.\ud For the generation of a Rankine vortex by a force field acting on an actuator disc with\ud thickness, an exact solution has been found in which not only the thrust and torque\ud determine the flow, but also a radial force. This force is conservative, in contrast to\ud the other force components. For rotor blades, a conservative normal and radial force\ud acting on the chordwise bound vorticity is present. This explains the experimentally\ud observed inboard motion of the tip vortex of model wind turbine rotors before the\ud wake induction field drives it outboard. Simulations by computational fluid mechanics\ud and a vortex panel code reproduce the inboard motion, but an actuator line analysis,\ud in which the chordwise vorticity is absent, does not. The conservative load is only\ud 1–2% of the thrust on the entire blade but =10% of the thrust at the tip (r/R>0.9).\ud Conservative forces at the disc and rotor blade vanish for vanishing disc thickness or\ud blade cross-section, so play no role in any of the infinitely thin actuator disc or line\ud methods. However, if higher-order effects of non-zero dimensions are to be modelled,\ud the conservative force field has to be included.peer-reviewe

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“…As noted in [23] (pp. [49][50][51][52][53], this moment is not generated by the advancing and retreating blade effect but by the skewed wake geometry which causes the trailing tip vorticity to be on average closer to the downwind side of the rotor plane. Figure 11.…”

Section: Wake Characteristicsmentioning

confidence: 99%

“…Such measurements have been performed by [50] and in the MEXICO experiment (see [51]). More recent PIV measurements include those undertaken at TUDelft [39,52], at NTNU [53] and at Monash University (see [44]). In the experiment by [50], PIV measurements were obtained at various blade azimuthal positions.…”

Section: Wake Characteristicsmentioning

confidence: 99%

A Review of Wind Turbine Yaw Aerodynamics

Micallef¹,

Sant²

2016

Wind Turbines - Design, Control and Applications

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The fundamental physics of HAWT aerodynamics in yaw is reviewed with reference to some of the latest scientific research covering both measurements and numerical modelling. The purpose of this chapter is to enable a concise overview of this important subject in rotor aerodynamics. This will provide the student, researcher or industry professional a quick reference. Detailed references are included for those who need to delve deeper into the subject. The chapter is also restricted to the aerodynamics of single rotors and their wake characteristics. Far wake and wind turbine to turbine effects experienced in wind farms are excluded from this review. Finally, a future outlook is provided in order to inspire further research in yawed aerodynamics.

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The origins of a wind turbine tip vortex

Cited by 21 publications

References 1 publication

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 role of conservative forces in rotor aerodynamics

A Review of Wind Turbine Yaw Aerodynamics

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