Comparison of the lifting-line free vortex wake method and the blade-element-momentum theory regarding the simulated loads of multi-MW wind turbines

Hauptmann, Stefan; Bülk, M.; Schön, L.; Erbslöh, S; Boorsma, K.; Grasso, Francesco; Kühn, Martin; Cheng, Po Wen

doi:10.1088/1742-6596/555/1/012050

Cited by 17 publications

(17 citation statements)

References 4 publications

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“…The common practice to modeling HAWT aerodynamics is through blade‐element momentum (BEM) theory. However, it has been shown that the accuracy of BEM deteriorates at high tip‐speed ratios (TSR) and that BEM also overpredicts some critical loads such as root‐bending moments (RBMs) . A higher fidelity solution can be obtained using the time‐domain unsteady vortex lattice method (UVLM), which, under attached flow conditions, captures three‐dimensional aerodynamic loads without the empirical corrections used in BEM .…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic load control in horizontal axis wind turbines with combined aeroelastic tailoring and trailing‐edge flaps

Palacios

Kerrigan

et al. 2015

Wind Energy

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This paper presents an aeroservoelastic modeling approach to investigate dynamic load alleviation in large wind turbines with composite blades and trailingedge aerodynamic surfaces. The tower and rotating blades are modeled using geometrically-nonlinear composite beams, and linearized about reference rotating conditions with potentially arbitrarily-large structural displacements. The aerodynamics of the rotor are represented using a linearized unsteady vortexlattice method and the resulting aeroelastic system is written in a state-space description that is both convenient for model reductions and control design. A linear model of a single blade is then used to design an H ∞ regulator, capable of providing load reductions of up to 13% in closed-loop on the full wind turbine nonlinear aeroelastic model. When combined with passive load alleviation through aeroelastic tailoring, dynamic loads can be further reduced to 35%. While the separate use of active flap controls and passive mechanisms for load alleviation have been well-studied, an integrated approach involving the two mechanisms has yet to be fully explored and is the focus of this paper. Finally, the possibility of exploiting torsional stiffness for active load alleviation on turbine blades is also considered. IntroductionHorizontal-Axis Wind Turbines (HAWT) have been steadily increasing in size since they were first considered for large-scale energy production, both in terms of tower height and rotor diameter [Barlas and van Kuik(2010)]. At the time of writing, the largest wind turbines in operation have rotors measuring above 120 m in diameter, but rotors of up to 160 m are already being developed. Larger blades are necessarily more flexible and, as a result, aeroelastic effects previously not seen in smaller rotors are beginning to surface [Hansen et al.(2006)Hansen, Sørensen, Voutsinas, Sørensen, This has brought about new needs in terms of modeling requirements and poses new technological challenges, in particular, with respect to an increased need for methods of load alleviation to prolong fatigue life [Bottasso et al.(2013)Bottasso, Campagnolo, Croce, and Tib Passive load alleviation through aeroelastic tailoring is attractive in its simplicity, design and is now well understood [Shirk et al.(1986)Shirk, Hertz, and Weisshaar]. It relies on a blade structure designed with bend-twist coupling (twist-towardsfeather) to reduce the angle of attack as the blade bends upwards. This mod-1

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Section: Introductionmentioning

confidence: 99%

Aerodynamic load control in horizontal axis wind turbines with combined aeroelastic tailoring and trailing‐edge flaps

Palacios

Kerrigan

et al. 2015

Wind Energy

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“…Riziotis, Manolas and Voutsinas, Gebhardt and Roccia, Branlard et al ,. Hauptmann et al . and Boorsma, Hartvelt and Orsi.…”

Section: Introductionmentioning

confidence: 99%

“…coupled a vortex code called Omnivor to the aeroelastic code HAWC2 using strong coupling. Hauptmann et al . coupled the free vortex wake code AWSM with the multi‐body simulation software package SIMPACK.…”

Section: Introductionmentioning

confidence: 99%

“…The coupling of MIRAS with HAWC2 is planned in the future. The aerodynamic tool, MIRAS, differs from the studies in that the blade geometry is represented in a 3D manner, and the viscous effects on the blade surface are taken into account using an integral boundary layer solver. A variety of simulation tests are provided to illustrate the versatility of MIRAS‐FLEX and how the results compare with other standardized codes.…”

Section: Introductionmentioning

confidence: 99%

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Development of an aeroelastic code based on three‐dimensional viscous–inviscid method for wind turbine computations

et al. 2017

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Aerodynamic and structural dynamic performance analysis of modern wind turbines are routinely estimated in the wind energy field using computational tools known as aeroelastic codes. Most aeroelastic codes use the blade element momentum (BEM) technique to model the rotor aerodynamics and a modal, multi‐body or the finite‐element approach to model the turbine structural dynamics. The present work describes the development of a novel aeroelastic code that combines a three‐dimensional viscous–inviscid interactive method, method for interactive rotor aerodynamic simulations (MIRAS), with the structural dynamics model used in the aeroelastic code FLEX5. The new code, called MIRAS‐FLEX, is an improvement on standard aeroelastic codes because it uses a more advanced aerodynamic model than BEM. With the new aeroelastic code, more physical aerodynamic predictions than BEM can be obtained as BEM uses empirical relations, such as tip loss corrections, to determine the flow around a rotor. Although more costly than BEM, a small cluster is sufficient to run MIRAS‐FLEX in a fast and easy way. MIRAS‐FLEX is compared against the widely used FLEX5 and FAST, as well as the participant codes from the Offshore Code Comparison Collaboration Project. Simulation tests consist of steady wind inflow conditions with different combinations of yaw error, wind shear, tower shadow and turbine‐elastic modeling. Turbulent inflow created by using a Mann box is also considered. MIRAS‐FLEX results, such as blade tip deflections and root‐bending moments, are generally in good agreement with the other codes. Copyright © 2017 John Wiley & Sons, Ltd.

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“…Vortex methods such as the Lifting Line Free Vortex Wake (LLFVW) aerodynamic model are able to model the turbine wake and its interaction with the turbine directly instead of relying on momentum balance equations -as BEM models do. Therefore, LLFVW models are able to calculate unsteady aerodynamics with far less assumptions than BEM models (Hauptmann et al, 2014;Perez-Becker et al, 2018). Using more accurate aerodynamic methods lowers model uncertainty, potentially lowering design loads and safety factors and ultimately leading to more competitive turbine designs.…”

mentioning

confidence: 99%

Is the Blade Element Momentum Theory overestimating Wind Turbine Loads? – A Comparison with a Lifting Line Free Vortex Wake Method

Perez‐Becker

Papi

Saverin

et al. 2019

Preprint

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Abstract. Load calculations play a key role in determining the design loads of different wind turbine components. State of the art in the industry is to use the Blade Element Momentum (BEM) theory to calculate the aerodynamic loads. Due to their simplifying assumptions of the rotor aerodynamics, BEM methods have to rely on several engineering correction models to capture the aerodynamic phenomena present in Design Load Cases (DLCs) with turbulent wind. Because of this, BEM methods can overestimate aerodynamic loads under challenging conditions when compared to higher-order aerodynamic methods - such as the Lifting Line Free Vortex Wake (LLFVW) method – leading to unnecessarily high design loads and component costs. In this paper, we give a quantitative answer to the question of BEM load overestimation by comparing the results of aeroelastic load calculations done with the BEM-based OpenFAST code and the QBlade code which uses a LLFVW method. We compare extreme and fatigue load predictions from both codes using 66 ten-minute load simulations of the DTU 10 MW Reference Wind Turbine according to the IEC 61400-1 power production DLC group. Results from both codes show differences in fatigue and extreme load estimations for practically all considered sensors of the turbine. LLFVW simulations predict 4 % and 14 % lower lifetime Damage Equivalent Loads (DELs) for the out-of-plane blade root and the tower base fore-aft bending moments, when compared to BEM simulations. The results also show that lifetime DELs for the yaw bearing tilt- and yaw moments are 2 % and 4 % higher when calculated with the LLFVW code. An ultimate state analysis shows that extreme loads of the blade root out-of-plane and the tower base fore-aft bending moments predicted by the LLFVW simulations are 3 % and 8 % lower than the moments predicted by BEM simulations, respectively. Further analysis reveals that there are two main contributors to these load differences. The first is the different treatment in both codes of the effect that sheared inflow has on the local blade aerodynamics and second is the wake memory effect model which was not included in the BEM simulations.

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Comparison of the lifting-line free vortex wake method and the blade-element-momentum theory regarding the simulated loads of multi-MW wind turbines

Cited by 17 publications

References 4 publications

Aerodynamic load control in horizontal axis wind turbines with combined aeroelastic tailoring and trailing‐edge flaps

Aerodynamic load control in horizontal axis wind turbines with combined aeroelastic tailoring and trailing‐edge flaps

Development of an aeroelastic code based on three‐dimensional viscous–inviscid method for wind turbine computations

Is the Blade Element Momentum Theory overestimating Wind Turbine Loads? – A Comparison with a Lifting Line Free Vortex Wake Method

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