An evaluation of several methods of determining the local angle of attack on wind turbine blades

Guntur, Srinivas; Sørensen, Niels N.

doi:10.1088/1742-6596/555/1/012045

Cited by 46 publications

(55 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the current study, however, it is neglected as the two verification environments, HAWC2 and EllipSys3D-Flex5, do not model the surface of the airfoils. Shen et al (2006Shen et al ( , 2009, Guntur and Sørensen (2014), and Rahimi et al (2018) present several methods to calculate the flow near the airfoil that also take 3-D effects into account, but the methods require information that cannot be obtained directly from a BMFS. Pedersen et al (2017) describes how to obtain the effective 3-D inflow from the relative wind speed and two perpendicular angles measured by a blade-mounted five-hole pitot, including compensation for bound circulation.…”

Section: Wind Speed From a Bmfsmentioning

confidence: 99%

Free-flow wind speed from a blade-mounted flow sensor

et al. 2018

View full text Add to dashboard Cite

Abstract. This paper presents a method for obtaining the free-inflow velocities from a 3-D flow sensor mounted on the blade of a wind turbine.From its position on the rotating blade, e.g. one-third from the tip, a blade-mounted flow sensor (BMFS) is able to provide valuable information about the turbulent sheared inflow in different regions of the rotor. At the rotor, however, the inflow is affected by the wind turbine, and in most cases the wind of interest is the inflow that the wind turbine is exposed to, i.e. the free-inflow velocities.The current method applies a combination of aerodynamic models and procedures to estimate the induced velocities, i.e. the disturbance of the flow field caused by the wind turbine. These velocities are subtracted from the flow velocities measured by the BMFS to obtain the free-inflow velocities. Aeroelastic codes, like HAWC2, typically use a similar approach to calculate the induction, but they use it for the reversed process, i.e. they add the induction to the free inflow to get the flow velocities at the blades, which are required to calculate the resulting aerodynamic forces.The aerodynamic models included in the current method comprise models based on blade element momentum (BEM) for axial and tangential induction, a radial induction model and tip loss correction, and models for skew and dynamic inflow.It is shown that the method is able to calculate the free-inflow velocities with high accuracy when applied to aeroelastic HAWC2 simulations with a stiff structural model while some deviations are seen in simulations with a flexible structure.Furthermore, the method is tested on simulations performed by a flexible structural model coupled with a large-eddy simulation (LES) flow solver. The results of this higher-fidelity verification confirm the HAWC2-based conclusion.

show abstract

Section: Wind Speed From a Bmfsmentioning

confidence: 99%

Free-flow wind speed from a blade-mounted flow sensor

et al. 2018

View full text Add to dashboard Cite

show abstract

“…by Johansen and Sørensen (2004) or Guntur and Sørensen (2014). In the present work, two methods for the evaluation of the induction factors and the local angles of attack at the blade were tested and compared.…”

Section: D)mentioning

confidence: 99%

“…Shen et al (2009) obtained the induced velocities and local angles of attack from the pressure distribution or the bound circulation around the blade. Guntur and Sørensen (2014) compared four different methods for the evaluation of the angle of attack from 3D CFD simulations, three of which provide the induction factors as well.…”

mentioning

confidence: 99%

“…In the present work, two different methods are used to obtain the induction factors: The first one is based on the evaluation of 15 the circumferentially averaged axial and tangential velocity in annular sections in a number of slices upstream and downstream of the rotor (method 2 from Guntur and Sørensen (2014); this had already been described before e.g. by Johansen and Sørensen (2004) and is sometimes referred to as azimuthal averaging technique (AAT)).…”

mentioning

confidence: 99%

“…by Johansen and Sørensen (2004) and is sometimes referred to as azimuthal averaging technique (AAT)). The second method is called the inverse BEM method (method 1 from Guntur and Sørensen (2014), already described in principle by Lindenburg (2003)). …”

mentioning

confidence: 99%

See 2 more Smart Citations

Updating BEM models with 3D rotor CFD data

Schneider

Nitzsche

Hennings

2016

Preprint

View full text Add to dashboard Cite

Abstract. In order to improve the prediction of aerodynamic forces on a wind turbine rotor by the blade element momentum method (BEM), airfoil coefficients are extracted from steady-state 3D RANS simulations of a rotor and then applied for steadystate simulations in a BEM code. The extraction is accomplished by using either averaging of velocities in annular sections, or an inverse BEM approach for determination of the local induction factors in the rotor plane. In this way, 3D rotor polars are obtained which are able to capture the rotational augmentation at the inner part of the blade as well as the load reduction 5 by 3D effects close to the blade tip. When using these 3D rotor polars, the radial force distribution from BEM is very close to the RANS result for a variety of load cases, whereas the deviation is often large with 2D airfoil coefficients. However, it is important that the polar extraction is completely consistent the the BEM code in which the polars are supposed to be used. The 3D rotor polars are shown to depend on the blade pitch angle. In addition, the accuracy of the slope of the 3D rotor polars and their feasibility for application in unsteady simulations is assessed by a quasi-steady comparison. This work is an updated and 10

show abstract

A study on rotational augmentation using CFD analysis of flow in the inboard region of the MEXICO rotor blades

Guntur

Sørensen

2014

Wind Energy

View full text Add to dashboard Cite

This work presents an analysis of data from existing as well as new full-rotor computational fluid dynamics computations on the MEXICO rotor, with focus on the flow around the inboard parts of the blades. The boundary layer separation characteristics on the airfoil sections in the inboard parts of the rotor are analysed using the pressure and the skin friction data at a range of angles of attack. These data are used to gain insight on the relative behaviour of separated boundary layers in 3D flow compared with 2D flow. It has been found that separation on airfoils in rotating flows is different from that in 2D flows in two respects: (i) there is a chord-wise postponement (or delay) of the separation point, and (ii) the angle of attack at which separation is initiated is higher in 3D compared with 2D. Comments are made on the mechanism of stall delay, and the main differences between the skin friction and pressure distribution behaviours in 2D and 3D rotating flows are highlighted.

show abstract

An evaluation of several methods of determining the local angle of attack on wind turbine blades

Cited by 46 publications

References 6 publications

Free-flow wind speed from a blade-mounted flow sensor

Free-flow wind speed from a blade-mounted flow sensor

Updating BEM models with 3D rotor CFD data

A study on rotational augmentation using CFD analysis of flow in the inboard region of the MEXICO rotor blades

Contact Info

Product

Resources

About