Investigations of the inflow turbulence effect on rotational augmentation by means of CFD

Bangga, Galih; Kim, Yusik; Lutz, Thorsten; Weihing, Pascal; Krämer, Ewald

doi:10.1088/1742-6596/753/2/022026

Cited by 17 publications

(10 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The model has been widely used for industrial and academic purposes and is well known to be able to deliver good predictions for flows involving a strong adverse pressure gradient and separation. This has been also shown by previous works, for examples as in [3,18,19,25,10,21,24]. Three variants of time step sizes will be investigated, namely ∆t = T /360, T /720 and T /1440 which are equivalent to 1 • , 0.5 • and 0.25 • blade rotation per physical time step, respectively.…”

Section: Computational Mesh and Numerical Setupmentioning

confidence: 70%

“…It shall be noted that the pole connector mesh was handled using the degenerate line boundary condition which allows a higher grid skewness on the pole boundary to be used. Several preceding works from the authors were carried out using this approach with good results [18,19,10,20,21]. The total number of grid points employed is of 327,524 divided into 92 different grid blocks.…”

Section: Computational Mesh and Numerical Setupmentioning

confidence: 99%

“…The CFD simulations were carried out using a block-structured solver FLOWer from the German Aerospace Center (DLR) [22]. The code has been developed during the last years for wind turbine applications [18][19][20]10]. The time integration is carried out by an explicit hybrid 5-stage Runge-Kutta scheme.…”

Section: Computational Mesh and Numerical Setupmentioning

confidence: 99%

See 2 more Smart Citations

Unsteady Navier-Stokes studies on loads, wake, and dynamic stall characteristics of a two-bladed vertical axis wind turbine

Bangga

Lutz

Dessoky

et al. 2017

Journal of Renewable and Sustainable Energy

Self Cite

View full text Add to dashboard Cite

Computational fluid dynamics (CFD) studies are carried out on a two-bladed vertical axis wind turbine (VAWT) operating at a wind speed of 8 m/s for the tip speed ratios (λ) of 0.50 -3.0. The blade consists of the NACA 0021 airfoil with the chord length of 0.265 m and a rotor radius of 1 m. Basic sensitivity studies for various time step sizes are carried out. The results are validated against available measurement data from literature. An excellent agreement is obtained for small λ up to optimum condition. For the higher tip speed ratios, the two dimensional CFD computations predict higher results than the wind tunnel experiment, but they are very similar to the field measurement data. Wake characteristics are presented in the present studies, showing that the wake becomes Gaussian at 5 times radius downsteam of the rotor. It is shown that complex flow phenomena occur due to dynamic stall onset especially for the smaller tip speed ratio.

show abstract

Section: Computational Mesh and Numerical Setupmentioning

confidence: 70%

Section: Computational Mesh and Numerical Setupmentioning

confidence: 99%

See 1 more Smart Citation

Unsteady Navier-Stokes studies on loads, wake, and dynamic stall characteristics of a two-bladed vertical axis wind turbine

Bangga

Lutz

Dessoky

et al. 2017

Journal of Renewable and Sustainable Energy

Self Cite

View full text Add to dashboard Cite

show abstract

“…This method has proven to produce reasonable results (Bangga et al, 2016;Klein et al, 2014), but it is only applicable for steady inflow conditions. But since in the 1 p case the reduced frequency is still very low with a value of 0.024 at mid-flap position, a quasi-steady approach is appropriate (Leishman, 2006).…”

Section: Comparison To Steady Flap Deflectionsmentioning

confidence: 99%

An investigation of unsteady 3-D effects on trailing edge flaps

et al. 2017

Self Cite

View full text Add to dashboard Cite

Abstract. The present study investigates the impact of unsteady 3-D aerodynamic effects on a wind turbine blade with trailing edge flap by means of computational fluid dynamics (CFD). Harmonic oscillations are simulated on the DTU 10 MW rotor with a morphing flap of 10 % chord extent ranging from 70 to 80 % blade radius. The deflection frequency is varied in the range between 1 and 6 p. To quantify 3-D effects, rotor simulations are compared to 2-D airfoil computations and the 2-D theory by Theodorsen. It was found that the deflection of the flap on the 3-D rotor causes a complex wake development and induction which influences the loads over large parts of the blade. In particular, the rotor near wake with its trailing and shed vortex structures revealed a great impact. Trailing vorticity, a 3-D phenomenon, is caused by the gradient of bound circulation along the blade span. Shed vorticity originates from the temporal bound circulation gradient and is thus also apparent in 2-D. Both lead to an amplitude reduction and shed vorticity additionally to a hysteresis of the lift response with regard to the deflection signal in the flap section. A greater amplitude reduction and a less pronounced hysteresis is observed on the 3-D rotor compared to the 2-D airfoil case. Blade sections neighboring the flap experience, however, an opposing impact and hence partly compensate for the negative effect of trailing vortices in the flap section with respect to integral loads. Comparisons to steady flap deflections at the 3-D rotor revealed the high influence of dynamic inflow effects.

show abstract

“…However, Zahle et al [26] and Bangga et al [27] noted that rotational augmentation is still prominent in the root region of a 10 MW modern pitch-controlled HAWT. Bangga et al [28] also observed the unsteady effects on rotational augmented blade loads under a turbulent inflow.…”

Section: Introductionsmentioning

confidence: 93%

Comparative Study of Dynamic Stall under Pitch Oscillation and Oscillating Freestream on Wind Turbine Airfoil and Blade

Zhu

Wang

2018

Applied Sciences

View full text Add to dashboard Cite

This study aims to assess the dynamic stall of the wind turbine blade undergoing pitch oscillation (PO) and oscillating freestream (OF), respectively. Firstly, a thin-airfoil theoretical analysis was performed to differentiate between these two dynamic effects. During upstroke, PO results in a positive effective airfoil camber, while OF has an additional negative effective airfoil camber, and yet in contrast during downstroke, PO decreases the effective camber, while OF increases the effective camber. Secondly, the equivalence relation between PO and OF is investigated by numerically solving the unsteady Reynolds-averaged Navier-Stokes equations. The difference between PO and OF mainly exists in the linear part of the aerodynamic loads. Because the difference is great at high reduced frequencies or angle of attack (AOA) amplitudes, PO and OF should be treated separately for dynamic stall from different aerodynamic sources. Thirdly, the Beddoes-Leishman dynamic model coupled with Bak's rotational stall delay model was used to predict the yawed responses of the blade section. The obtained results show different aerodynamic responses between PO and OF, although consideration of rotational augmentation can greatly improve the accuracy of the lift and drag coefficients. To improve the understanding and coupling modeling of rotational augmentation and dynamic stall, an extended analysis of the coupled effect was performed as well.

show abstract

Investigations of the inflow turbulence effect on rotational augmentation by means of CFD

Cited by 17 publications

References 17 publications

Unsteady Navier-Stokes studies on loads, wake, and dynamic stall characteristics of a two-bladed vertical axis wind turbine

Unsteady Navier-Stokes studies on loads, wake, and dynamic stall characteristics of a two-bladed vertical axis wind turbine

An investigation of unsteady 3-D effects on trailing edge flaps

Comparative Study of Dynamic Stall under Pitch Oscillation and Oscillating Freestream on Wind Turbine Airfoil and Blade

Contact Info

Product

Resources

About