The influence of free stream turbulence on the development of a wind turbine wake

Gambuzza, Stefano; Ganapathisubramani, Bharathram

doi:10.1017/jfm.2023.302

Cited by 15 publications

(5 citation statements)

References 83 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the presence of freestream turbulence, the tip vortices break down earlier and the wake recovers faster, leading to a shorter near wake (Chamorro & Porté-Agel 2009; Wu & Porté-Agel 2012). Recently, Gambuzza & Ganapathisubramani (2023) studied the effect of both freestream turbulence intensity () and integral time scale. They tested from to , and integral time scales times the convective time scale based on turbine diameter.…”

Section: On the Definition Of Near Wakementioning

confidence: 99%

“…(2021) defined the near wake's extent as the distance where the time-averaged coherent kinetic energy dropped to a certain level. Gambuzza & Ganapathisubramani (2023) defined the near wake to be the region where the material derivative of turbulent kinetic energy is positive.…”

Section: On the Definition Of Near Wakementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Hence breakdown of the tip vortices is a necessary process to re-energise the wake in the far field, reducing the velocity deficit, which is beneficial for the subsequent turbines in the grid. In the presence of freestream turbulence, the tip vortices were found to break down early, leading to faster wake recovery (Chamorro & Porté-Agel 2009;Wu & Porté-Agel 2012;Gambuzza & Ganapathisubramani 2023). Chamorro et al (2013) studied the performance of a hydrokinetic turbine in a turbulent open channel flow, and showed a coupling between the spectral content of the turbine's performance and the low-frequency content of the inflow turbulence.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effect of tip speed ratio on coherent dynamics in the near wake of a model wind turbine

Biswas,

Buxton

2024

J. Fluid Mech.

View full text Add to dashboard Cite

The near wake of a small-scale wind turbine is investigated using particle image velocimetry experiments at different tip speed ratios ( $\lambda$ ). The wind turbine model had a nacelle and a tower mimicking real-scale wind turbines. The near wake is found to be dominated by multiple coherent structures, including the tip vortices, distinct vortex sheddings from the nacelle and tower, and wake meandering. The merging of the tip vortices is found to be strongly dependent on $\lambda$ . A convective length scale ( $L_c$ ) related to the pitch of the tip vortices is defined that is shown to be a better length scale than turbine diameter ( $D$ ) to demarcate the near wake from the far wake. The tower induced strong vertical asymmetry in the flow by destabilising the tip vortices and promoting mixing in the lower (below the nacelle) plane. The nacelle's shedding is found to be important in ‘seeding’ wake meandering, which, although not potent, exists close to the nacelle, and it becomes important only after a certain distance downstream ( $x>3L_c$ ). A link between the ‘effective porosity’ of the turbine and $\lambda$ is established, and the strength and frequency of wake meandering are found to be dependent on $\lambda$ . In fact, a decreasing trend of wake meandering frequency with $\lambda$ is observed, similar to vortex shedding from a porous plate at varying porosity. Such similarity upholds the notion of wake meandering being a global instability of the turbine, which can be considered as a ‘porous’ bluff body of diameter $D$ .

show abstract

Section: On the Definition Of Near Wakementioning

confidence: 99%

Section: On the Definition Of Near Wakementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of tip speed ratio on coherent dynamics in the near wake of a model wind turbine

Biswas,

Buxton

2024

J. Fluid Mech.

View full text Add to dashboard Cite

show abstract

“…They found that higher incoming turbulence levels help the entrainment of external flow and mixing resulting in faster wake recovery. Gambuzza & Ganapathisubramani (2023) decoupled the effect of the free stream turbulence from the integral time scales on the wake flows, showing that higher integral time scales result in a slower wake evolution (mimicking lower-turbulence inflow conditions) irrespective of the turbulence ambient levels.…”

Section: Introductionmentioning

confidence: 99%

Wind turbine wakes: experimental investigation of two-point correlations and the effect of stable thermal stability

Placidi,

Hancock,

Hayden

2023

J. Fluid Mech.

View full text Add to dashboard Cite

Wind tunnel experiments are performed in both neutral and stable boundary layers to study the effect of thermal stability on the wake of a single turbine and on the wakes of two axially aligned turbines, thereby also showing the influence of the second turbine on the impinging wake. In the undisturbed stable boundary layers, the turbulence length scales are significantly smaller in the vertical and longitudinal directions (up to 50 % and $\approx$ 40 %, respectively), compared with the neutral flow, while the lateral length scale is unaffected. The reductions are larger with the imposed inversion of a second stable case, except in the near-wall region. In the neutral case, the length scales in the wake flow of the single turbine are reduced both vertically and laterally (up to 50 % and nearly 40 %, respectively). While there is significant upstream influence of a second turbine (on mean and turbulence quantities), there is virtually no upstream effect on vertical length scales. However, curiously, the presence of the second turbine aids length-scale recovery in both directions. Longitudinally, each turbine contributes to successive reduction in coherence. The effect of stability on the turbulence length scales in the wake flows is non-trivial: at the top of the boundary layer, the reduction in the wall-normal length scale is dominated by the thermal effect, while closer to the wall, the wake processes strongly modulate this reduction. Laterally, the turbines’ rotation promotes asymmetry, while stability opposes this tendency. The longitudinal coherence, significantly reduced by the wake flows, is less affected by the boundary layer's thermal stability.

show abstract

Experimental study of the wake interaction between two vertical axis wind turbines

Huang,

Vijaykumar Patil,

Sciacchitano

et al. 2023

Wind Energy

View full text Add to dashboard Cite

Wakes and wake interactions in wind turbine arrays diminish energy output and raise the risk of structural fatigue; hence, comprehending the features of rotor–wake interactions is of practical relevance. Previous studies suggest that vertical axis wind turbines (VAWTs) can facilitate a quicker wake recovery. This study experimentally investigates the rotor–wake and wake–wake interaction of VAWTs; different pitch angles of the blades of the upwind VAWT are considered to assess the interactions for different wake deflections. With stereoscopic particle image velocimetry, the wake interactions of two VAWTs are analysed in nine distinct wake deflection and rotor location configurations. The time‐average velocity fields at several planes upwind and downwind from the rotors are measured. Additionally, time‐average loads on the VAWTs are measured via force balances. The results validate the rapid wake recovery and the efficacy of wake deflection, which increases the available power in the second rotor.

show abstract

The influence of free stream turbulence on the development of a wind turbine wake

Cited by 15 publications

References 83 publications

Effect of tip speed ratio on coherent dynamics in the near wake of a model wind turbine

Effect of tip speed ratio on coherent dynamics in the near wake of a model wind turbine

Wind turbine wakes: experimental investigation of two-point correlations and the effect of stable thermal stability

Experimental study of the wake interaction between two vertical axis wind turbines

Contact Info

Product

Resources

About