Analysis of Interactional Aerodynamics in Multi-Rotor Wind Turbines using Large Eddy Simulations

Hebbar, Ullhas; Rane, Jitesh D.; Gandhi, Farhan; Sahni, Onkar

doi:10.2514/6.2020-1489

Cited by 5 publications

(5 citation statements)

References 18 publications

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“…In 2016, Vestas Wind Energy Systems A/S developed and built a multirotor wind turbine demonstrator located in the Technical University of Denmark (DTU), Campus Risø, which consists of four rotors arranged in both top and bottom pairs. [5][6][7] Pelagic Power AS designed the concept of W2Power, a floating platform for combined extraction of Wind & Wave energy, accommodating two standard offshore wind turbines. 8 Similarly, Flowocean AB developed the FLOW concept, which uses two turbines on the same platform.…”

Section: Introductionmentioning

confidence: 99%

“…In this scenario, novel multirotor (and multiturbine) concepts have been developed, aiming to improve the performance of wind farms through increasing the power density while reducing number of platforms and costs associated to cable layout and cable efficiency. In 2016, Vestas Wind Energy Systems A/S developed and built a multirotor wind turbine demonstrator located in the Technical University of Denmark (DTU), Campus Risø, which consists of four rotors arranged in both top and bottom pairs 5–7 . Pelagic Power AS designed the concept of W2Power, a floating platform for combined extraction of Wind & Wave energy, accommodating two standard offshore wind turbines 8 .…”

Section: Introductionmentioning

confidence: 99%

“…Both numerical approaches predicted a power increase of around 3%. In Hebbar et al, 6 a multirotor system (four rotors) was analyzed using the actuator line model (ALM) approach for studying its wake recovery process showing a early onset when compared to a single rotor simulation. Van der Laan et al predicted an increase in the annual energy production (AEP) of of 0.3%–1.7% 11 in a wind farm array with 4

\times

4 (16 turbines) arrangement with four rotor units compared to the same array employing single rotor units with equivalent diameter.…”

Section: Introductionmentioning

confidence: 99%

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Aerodynamic performance of a dual turbine concept characterized by a relatively close distance between rotors

et al. 2023

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In this work, a closely spaced dual turbine concept is studied. The distance between the two side‐by‐side hubs is 1.05 D, where D is the rotor diameter. This configuration has a potential benefit for offshore wind developments in which power density can be maximized. The main goal is to evaluate the overall aerodynamic performance, blade loads, and wake structure of a reference wind turbine generator operating within this dual turbine configuration and to compare the effects against those for the typical single turbine configuration. For this purpose, an actuator line model has been employed together with the large eddy simulation approach for predicting the turbulence effects. This model was implemented by using the open‐source computational fluid dynamics toolbox OpenFOAM. Results show a better performance for the dual turbine concept. Under same operating conditions, the aerodynamic power of each turbine within the dual concept is higher than the power of the stand alone turbine, particularly at lower operating wind speeds (approximately 2% to 3% of extra power per turbine). Comparison between the two configurations shows similar character of the tangential and normal forces acting on the blades in terms of magnitude and fluctuation, eliminating potential concerns regarding fatigue and blade design. The largest difference in the tangential and normal root bending moments are approximately 3% and 2%, respectively, between single and dual turbine configurations. Finally, wake recovery analysis shows a downwind velocity deficit that is not enhanced streamwise in the dual turbine configuration with no considerable difference after 7 D.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

\times

4 (16 turbines) arrangement with four rotor units compared to the same array employing single rotor units with equivalent diameter.…”

Section: Introductionmentioning

confidence: 99%

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Aerodynamic performance of a dual turbine concept characterized by a relatively close distance between rotors

et al. 2023

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“…Compared to single-rotor wind turbines, multi-rotor wind turbines have some advantages, not only in terms of power output but also in terms of wake recovery. Hebbar et al [11] researched multi-rotor wind turbines using an LES (large eddy simulation) with an actuation line model to analyze the effect of incoming shear flow on wake recovery. Multi-rotor wind turbine structures showed earlier wake recovery, less velocity deficit, and better wake uniformity than single-rotor structures.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Effect of the Blade Tip Distance on the Power and the Wake Recovery with Small Multi-Rotor Wind Turbines

Gong

Pan

Yang

et al. 2023

JMSE

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In order to investigate the output power and wake velocity of small multi-rotor wind turbines compared to single-rotor wind turbines, which operate in the same swept area at various blade tip distances, this paper used the wind tunnel test method to examine single-rotor wind turbines with diameter D of 0.4 m and 0.34 m corresponding to the triple-rotor wind turbines and double-rotor wind turbines with a single rotor diameter D of 0.24 m, respectively. The experimental results indicated that, without rotation speed control, the triple-rotor wind turbine produced more power than the single-rotor wind turbine with an equivalent swept area and that the output power tended to rise initially and then fall as the distance between each rotor increased. Moreover, the power increase reached a maximum of 8.4% at the 0.4D blade tip distance. In terms of wake measurement, triple-rotor wind turbines had smaller wake losses and faster recovery rates than single-rotor wind turbines. The smaller the blade tip distance, the earlier the wake merged and fused and the faster the recovery rate. In designing small multi-rotor wind turbines, the above discussion can serve as a guide.

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“…Some extended work regarding the utilization of the combined ALM-LES method to simulate the atmosphere boundary layer effect has been conducted by Lu and Porté-Agel [37], with turbulence modeled through a Lagrangian scale-dependent subgrid-scale (SGS) model. Hebbar et al [38] has studied the effect of incoming turbulence on shear layer breakdown and the wake recovery effects of multi-rotor wind turbines using the ALM-LES method. Martínez-Tossas et al [39] compared four large eddy simulation research codes and the effect of model coefficients on wake flow in actuator line based wind turbine modeling.…”

Section: Introductionmentioning

confidence: 99%

CFD Simulation of Co-Planar Multi-Rotor Wind Turbine Aerodynamic Performance Based on ALM Method

et al. 2022

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Considering requirements such as enhanced unit capacity, the geometric size of wind turbine blades has been increasing; this, in turn, results in a rapid increase in manufacturing costs. To this end, in this paper, we examine the aerodynamics of co-planar multi-rotor wind turbines to achieve higher unit capacity at a lower blade length. The multiple wind rotors are in the same plane with no overlaps. The ALM-LES method is used to investigate the interaction effect of the blade tip vortices, by revealing the regulation of aerodynamic performance and flow field characteristics of the multi-rotor wind turbines. The simulated results suggest an observable reduction in the blade tip vortices generated by blades located closely together, due to the breaking and absorption of the blade tip vortices by the two rotors. This results in increased aerodynamic performance and loads on the multi-rotor wind turbine. The influence between the blade tip vortex is mainly located in the range of 0.2 R from the blade tip, with this range leading to a significant increase in the lift coefficient. Thus, when the wind rotor spacing is 0.2 R, the interaction between the blade tip vortices is low.

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Analysis of Interactional Aerodynamics in Multi-Rotor Wind Turbines using Large Eddy Simulations

Cited by 5 publications

References 18 publications

Aerodynamic performance of a dual turbine concept characterized by a relatively close distance between rotors

Aerodynamic performance of a dual turbine concept characterized by a relatively close distance between rotors

Experimental Study on the Effect of the Blade Tip Distance on the Power and the Wake Recovery with Small Multi-Rotor Wind Turbines

CFD Simulation of Co-Planar Multi-Rotor Wind Turbine Aerodynamic Performance Based on ALM Method

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