A study on rotational effects and different stall delay models using a prescribed wake vortex scheme and NREL phase VI experiment data

Breton, Simon-Philippe; Coton, F. N.; Moe, Geir

doi:10.1002/we.269

Cited by 99 publications

(83 citation statements)

References 22 publications

(33 reference statements)

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“…Such effects are called "rotation effects" [28] and appear to be due to centrifugal and Coriolis forces [29,30]. Various corrections have been proposed for the aerodynamic coefficients [30], but none provides good correlation for the predictions with the experiments. In the present model, the following correction is proposed, limited to the normal force:…”

Section: D Effectsmentioning

confidence: 99%

Modeling Aerodynamics, Including Dynamic Stall, for Comprehensive Analysis of Helicopter Rotors

Truong

2017

Aerospace

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Abstract:To fulfill the objective of a predictive tool for rotorcraft, comprehensive analysis (CA) needs to be capable of providing both accurate and time-efficient predictions of rotor air loads and structural loads. The more recent methodology based on comprehensive analysis coupled with high-fidelity computational fluid dynamics (CFD) has shown improved predictions of air loads, but it has not the strength of computational efficiency and the versatility of stand-alone CA. The present article is concerned with modeling aerodynamics about helicopter rotors for CA. The aerodynamics about rotors are very complex, encompassing subsonic to transonic flow with unsteady, stalled behavior and 3D effects. CA treats aerodynamics as separated into local and global flows. Semi-empirical models of dynamic stall were created in the 1970s-1990s for modeling unsteady local aerodynamics, including stalled flow. Most of them fail to provide good predictions of experimental results and also suffer problems of numerical convergence. The main effort in this study is about modeling local aerodynamics based on the revised "ONERA-Hopf bifurcation model". It is implemented in the comprehensive analysis code of ONERA according to a scheme that ensures numerical convergence. The experimental results obtained in the Wind Tunnel S1 of Modane (France) in 1991 on the Rotor 7A are considered for validation of the analysis under three flight test conditions: high-speed test, high-thrust tests with light stall and deep stall, respectively. There is a reasonable agreement between the predictions of CA with experimental results. The distinct features of the stall model are the modeling of the boundary-layer effects and the vortex-shedding phenomenon.

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Section: D Effectsmentioning

confidence: 99%

Modeling Aerodynamics, Including Dynamic Stall, for Comprehensive Analysis of Helicopter Rotors

Truong

2017

Aerospace

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“…Chaviaropoulos and Hansen, 2000;Bak et al, 2006;Raj, 2000;Corrigan and Schillings, 1994). However, Breton et al (2008) and Guntur et al (2011) proved that their accuracy is still a critical issue. Currently, a major impediment in the development of accurate correction models is the incomplete understanding of the physical mechanisms.…”

Section: Spanwise Flows and Himmelskamp Effectmentioning

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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“…The three-dimensional rotational effect is one of the typical differences between rotating rotor and fixed wing, resulting in stall delay, which is characterized by significantly increased lift coefficient compared with the corresponding two-dimensional case, and by a delay in the occurrence of flow separation to higher angles of attack. In [29], a comparison of six models is made to illustrate the significance of stall delay models and some defects in these models. The Du-Selig stall-delay model [30], which is coupled into the FVW model, is used to modify the aerofoil aerodynamic data by consideration of the three-dimensional rotational effect in this work.…”

Section: (F) Unsteady Wake Under Platform Motionsmentioning

confidence: 99%

Unsteady aerodynamic analysis for offshore floating wind turbines under different wind conditions

Wang

Yuan

et al. 2015

Phil. Trans. R. Soc. A.

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A free-vortex wake (FVW) model is developed in this paper to analyse the unsteady aerodynamic performance of offshore floating wind turbines. A time-marching algorithm of third-order accuracy is applied in the FVW model. Owing to the complex floating platform motions, the blade inflow conditions and the positions of initial points of vortex filaments, which are different from the fixed wind turbine, are modified in the implemented model. A threedimensional rotational effect model and a dynamic stall model are coupled into the FVW model to improve the aerodynamic performance prediction in the unsteady conditions. The effects of floating platform motions in the simulation model are validated by comparison between calculation and experiment for a small-scale rigid test wind turbine coupled with a floating tension leg platform (TLP). The dynamic inflow effect carried by the FVW method itself is confirmed and the results agree well with the experimental data of a pitching transient on another test turbine. Also, the flapping moment at the blade root in yaw on the same test turbine is calculated and compares well with the experimental data. Then, the aerodynamic performance is simulated in a yawed condition of steady wind and in an unyawed condition of turbulent wind, respectively, for a largescale wind turbine coupled with the floating TLP motions, demonstrating obvious differences in rotor performance and blade loading from the fixed wind turbine. The non-dimensional magnitudes of loading changes due to the floating platform motions decrease from the blade root to the blade tip.

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A study on rotational effects and different stall delay models using a prescribed wake vortex scheme and NREL phase VI experiment data

Cited by 99 publications

References 22 publications

Modeling Aerodynamics, Including Dynamic Stall, for Comprehensive Analysis of Helicopter Rotors

Modeling Aerodynamics, Including Dynamic Stall, for Comprehensive Analysis of Helicopter Rotors

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

Unsteady aerodynamic analysis for offshore floating wind turbines under different wind conditions

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