The effect of tip speed ratio on a vertical axis wind turbine at high Reynolds numbers

Parker, Colin M.; Leftwich, Megan C.

doi:10.1007/s00348-016-2155-3

Cited by 51 publications

(24 citation statements)

References 13 publications

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“…The asymmetry of the wake in the horizontal plane can also be observed in this figure which is the inherent characteristic of VAWT wakes and is mainly related to the rotation of the turbine. Similar behavior has been reported in previous numerical and experimental studies of the wake of VAWTs [3,5,8,17,[70][71][72][73]. The vertical and lateral profiles of the mean streamwise velocity at the turbine equator are also plotted in Figure 4 for five different downstream locations at x/D = 1, 3, 7, 15 and 24.…”

Section: Numerical Setupsupporting

confidence: 83%

Impact of Subgrid-Scale Modeling in Actuator-Line Based Large-Eddy Simulation of Vertical-Axis Wind Turbine Wakes

Abkar

2018

Atmosphere

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A large-eddy simulation (LES) study of vertical-axis wind turbine wakes under uniform inflow conditions is performed. Emphasis is placed on exploring the effects of subgrid-scale (SGS) modeling on turbine loading as well as on the formation and development of the wind turbine wake. In this regard, the validated LES framework coupled with an actuator-line parametrization is employed. Three different SGS models are considered: the standard Smagorinsky model, the Lagrangian scale-dependent dynamic (LSDD) model, and the anisotropic minimum dissipation (AMD) model. The results show that the SGS model has a negligible effect on the mean aerodynamic loads acting on the blades. However, the structure of the wake, including the mean velocity and turbulence statistics, is significantly affected by the SGS closure. In particular, the standard Smagorisnky model with its theoretical model coefficient (i.e., C S ∼ 0.16) postpones the transition of the wake to turbulence and yields a higher velocity variance in the turbulent region compared to the LSDD and AMD models. This observation is elaborated in more detail by analyzing the resolved-scale turbulent kinetic energy budget inside the wake. It is also shown that, unlike the standard Smagorinsky model, which requires detailed calibrations of the model coefficient, the AMD can yield predictions similar to the LSDD model for the mean and turbulence characteristics of the wake without any tuning.

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Section: Numerical Setupsupporting

confidence: 83%

Impact of Subgrid-Scale Modeling in Actuator-Line Based Large-Eddy Simulation of Vertical-Axis Wind Turbine Wakes

Abkar

2018

Atmosphere

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“…This may be the reason why the TSRs play the most important role on Cp of VAWT, and it is insensitive to Factor D. According to the calculations of factor effect value and the previous research results, it can be seen that the rank of influence strength of these factors in As shown in Figure 16b, the effect value of Factor A is much higher than that of other factors. This means that as the influence of TSRs act on the whole process of operation of VAWT, the TSRs play an important role in the power output of VAWT, the similar conclusion can be also found in the literature [53], for VAWT, there is a strong dependence on for TSRs. In addition, the effect value of Factor C is also higher than that of Factor B and D. This is mainly because the boundary layer separation point can be delayed by increasing the k s /d s , and this results in the downstream blades being less affected by the shedding vortices.…”

Section: Power Coefficients Of Vawt In Taguchi Approachsupporting

confidence: 79%

Numerical Investigations of the Effects of the Rotating Shaft and Optimization of Urban Vertical Axis Wind Turbines

et al. 2018

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The central shaft is an important and indispensable part of a small scale urban vertical axis wind turbines (VAWTs). Normally, it is often operated at the same angular velocity as the wind turbine. The shedding vortices released by the rotating shaft have a negative effect on the blades passing the wake of the wind shaft. The objective of this study is to explore the influence of the wake of rotating shaft on the performance of the VAWT under different operational and physical parameters. The results show that when the ratio of the shaft diameter to the wind turbine diameter (α) is 9%, the power loss of the wind turbine in one revolution increases from 0% to 25% relative to that of no-shaft wind turbine (this is a numerical experiment for which the shaft of the VAWT is removed in order to study the interactions between the shaft and blade). When the downstream blades pass through the wake of the shaft, the pressure gradient of the suction side and pressure side is changed, and an adverse effect is also exerted on the lift generation in the blades. In addition, α = 5% is a critical value for the rotating shaft wind turbine (the lift-drag ratio trend of the shaft changes differently). In order to figure out the impacts of four factors; namely, tip speed ratios (TSRs), α, turbulence intensity (TI), and the relative surface roughness value (k s /d s ) on the performance of a VAWT system, the Taguchi method is employed in this study. The influence strength order of these factors is featured by TSRs > k s /d s > α > TI. Furthermore, within the range we have analyzed in this study, the optimal power coefficient (C p ) occurred under the condition of TSR = 4, α = 5%, k s /d s = 1 × 10 −2 , and TI = 8%.

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“…Tarhan and Yilmaz [12] investigated the Reynolds number effect on the lift, drag, and lift/drag coefficients of 14 small wind turbine airfoils with both wind tunnel tests and numerical simulations. Meanwhile, the Reynolds number effect on VAWTs has also received much attention [13,14]. With the increase in rotor size, the difference in the Reynolds numbers between the real-sized turbine and the model turbine becomes more obvious and its effect could not be omitted.…”

Section: Introductionmentioning

confidence: 99%

Wake Effect of a Horizontal Axis Wind Turbine on the Performance of a Downstream Turbine

et al. 2019

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This paper presents wind tunnel tests on the wake characteristics of a three-blade horizontal axis wind turbine and the wake effect on the performance of a downstream turbine. For a single turbine model, the performance was determined and this was followed by measurement of the wind characteristics including velocities, turbulence intensities, and correlation in the wake flow field. Subsequently, taking two horizontal axis wind turbines in a tandem arrangement into account, their performance was tested and the aerodynamic mechanism was discussed. The results showed that the upstream turbine with blades set at a small pitch angle provided smaller disturbance to the flow, but as the blade turned faster, larger changes in the velocity and the turbulence intensity occurred in its wake due to the more frequent disturbance of the wind turbine. The correlation of wake velocities in the turbine swept area also obviously decreased from the free-stream situation. For the downstream turbine, the output power loss largely depended on the wake characteristics of the upstream turbine, which was closely related to lower wind velocities or higher turbulence intensities. The decrease in correlation of the streamwise velocity within the blade swept area is accompanied by the increased correlation of the tangential velocity, which may be beneficial to the downstream turbine’s performance.

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The effect of tip speed ratio on a vertical axis wind turbine at high Reynolds numbers

Cited by 51 publications

References 13 publications

Impact of Subgrid-Scale Modeling in Actuator-Line Based Large-Eddy Simulation of Vertical-Axis Wind Turbine Wakes

Impact of Subgrid-Scale Modeling in Actuator-Line Based Large-Eddy Simulation of Vertical-Axis Wind Turbine Wakes

Numerical Investigations of the Effects of the Rotating Shaft and Optimization of Urban Vertical Axis Wind Turbines

Wake Effect of a Horizontal Axis Wind Turbine on the Performance of a Downstream Turbine

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