Research of asymmetric airfoil on aerodynamic characteristics of vertical axis wind turbines

Abstract

Asymmetric airfoils are commonly used in horizontal axis wind turbines, while symmetrical airfoils are currently the focal point of the researches for most vertical axis wind turbines’ airfoils studies. The purpose of this paper is to research the influence of asymmetric airfoils on the aerodynamic performance of vertical axis wind turbines. The influence of asymmetric airfoils on the aerodynamic characteristics of vertical axis wind turbines is investigated by numerical simulation method. The symmetric airfoils are chosen as NACA0021, while the asymmetric airfoils are chosen as DU97-W-300. Single-blade, 3-blade, different tip speed ratios, and three wind speeds (7, 8, 9 m/s) are set as the parameters. The wind turbine with symmetric airfoils performed better aerodynamically at high tip speed ratios, whereas the wind turbine with asymmetric airfoils performs well at low tip speed ratios. The wind turbine with asymmetric airfoils has outstanding start ability at low wind speeds.

Keywords

Asymmetric airfoil symmetric airfoil vertical axis wind turbine utilization rate of wind energy aerodynamic characteristics

Introduction

The rapid development of science and technology has led to a deepening in the consumption of non-renewable fuels and greenhouse gas emissions. This has resulted in serious environmental pollution. The world’s energy structure has also changed, and countries are stepping up their use of renewable energy (Ryberg et al., 2020). Since the turn of the century, the world’s population has been growing rapidly, and as a result, energy consumption has also been rising. Renewable energy mainly refers to material energy, such as solar, wind, geothermal, and water energy. One of the most promising of these is wind energy, which has the benefits of being plentiful, widely available, renewable, and pollution-free (Roy and Saha, 2013). Wind power is currently the most researched means of using wind energy.

Wind energy is frequently captured by transforming it into mechanical energy using wind turbines. Based on the orientation of the wind turbine’s main shaft, vertical axis wind turbines (VAWTs) and horizontal axis wind turbines (HAWTs) are two categories of wind turbines (Gulve and Barve, 2014). While HAWTs are used more broadly than VAWTs, the latter have the following advantages over the former such as no need for wind (wind can come from any direction into vertical axis wind turbines) (Manfrida and Talluri, 2020; Zhu et al., 2018), simple blade structures for processing and manufacturing, low noise, robust structures (subject to constant load) (Armstrong et al., 2012; Tjiu et al., 2015), suitable for urban environments (vertical axis wind turbines are not sensitive to changes in wind speed and direction), which can be used in any location (Bedon et al., 2014; Li et al., 2016). However, vertical axis wind turbines have lower efficiency than horizontal axis wind turbines, so research on improving the aerodynamic performance of vertical axis wind turbines is a priority today.

Currently, symmetric airfoils are more frequently used in vertical axis wind turbines and most of the researches are on symmetric airfoils. El-Samanoudy et al. investigated the aerodynamic performance of the vertical axis wind turbine with NACA0024 airfoils by varying the airfoils, number of blades, pitch angles, radius of rotation, and blade chord length (El-Samanoudy et al., 2010). Brusca et al. analyzed the performance of symmetric straight-blade wind turbines using a multi-stream tube model with changing aspect ratio. It enhanced the efficiency of the wind turbines because the Reynolds number rose as the aspect ratio fell (Brusca et al., 2014). Wang et al. designed a new Darrieus wind turbine that automatically deforms to the desired geometry to achieve better aerodynamic performance (Wang et al., 2016). Ferreira and Geurts derived the airfoil aerodynamic optimization expression as a function of lift slope and drag. It used a genetic optimization algorithm to allow the objective function to generate an airfoil shape that reduces the rotor mass without affecting the aerodynamic performance (Ferreira and Geurts, 2015). Manatbayev et al. performed icing simulations for vertical axis wind turbine blades. The conclusions drawn were that not significantly affect aerodynamic performance in rime ice conditions. In contrast, in glaze ice conditions, the uneven ice shape leads to significant airflow separation and lift reduction. Iced VAWTs lose up to 60% of their power performance due to icing conditions (Manatbayev et al., 2021). Wu et al. proposed a bi-directional coupled Euler-Lagrange multiphase approach to research the rotational and oscillatory performance of the NACA0015 airfoils under rain conditions (Wu et al., 2017). Hohman et al. researched the impact of the blade geometry on the wake structure of wind turbines. The results of experimental research on the influence of HR particle image velocimetry on the wake characteristics of vertical axis wind turbines were used as the basis (Hohman et al., 2020). Using CFD simulations, Hassanpour and Azadani improved the positioning of a pair of vertical axis wind turbines. It was determined that when wind turbines were positioned side by side with the equivalent altitude and the smallest horizontal spacing, their ability to generate power was maximized (Hassanpour and Azadani, 2021). The current symmetric airfoils are the reference to aviation airfoils such as NACA0018, NACA0021, and other airfoils.

Current researches on vertical axis wind turbines with asymmetric airfoils are scarce. Bausas and Danao investigated the aerodynamic characteristics of an experimental model with cambered blades in the non-constant wind by numerical simulation method. It showed that the VAWT blades with 1.5% camber showed the best performance (Bausas and Danao, 2015). Feng et al. analyzed the static torque coefficient, output power, and blade friction coefficient under static and dynamic conditions for vertical axis wind turbines with asymmetric airfoils S809, S1046, and symmetric airfoils NACA0018. It was concluded that vertical axis wind turbines with the S1046 airfoils had better dynamic aerodynamic characteristics (Feng et al., 2018). Subramanian et al. conducted a numerical simulation method of small asymmetric airfoil vertical axis wind turbines. It was revealed that an increase in the relative thickness of the airfoil within a certain range can raise the efficiency of the model. And wind turbine blades can be easily separated at large angles of attack (Subramanian et al., 2017).

The subject of this paper is the influence of symmetric and asymmetric airfoils on the aerodynamic performance of vertical axis wind turbines under multiple working situations. Both two wind turbine models have three blades. The utilization rate of wind energy is compared and analyzed in three constant wind environments at multiple tip speed ratios. And the aerodynamics of the two types of airfoils is further examined by observing velocity contours and vortex contours.

Numerical method

Model parameters

Listed in Table 1 are the essential parameters of the wind turbines with symmetric airfoils NACA0021 and asymmetric airfoils DU97-W-300 models.

Table 1.

Wind turbines model parameters.

Denomination	Value
Blade number (N)	3
Blade airfoil (attended)	NACA0021, DU97-W-300
Height(H) [m]	0.8
Radius(R) [m]	1
Chord(C) [m]	0.2
Wind speed(V) [m/s]	7,8,9

The original airfoil, also known as the symmetrical airfoil, is a typical airfoil with a straight mid-arc with identical flow characteristics at positive and negative angles of attack. The asymmetric airfoil, which is frequently employed in axial fans and compressors (Yilmaz et al., 2018), is a curved mid-arc airfoil with variable flow characteristics at positive and negative angles of attack. The airfoil blade is an important part of wind energy capture, and its selection plays a crucial part in the aerodynamic characteristics of the experimental models.

Two types of airfoils are represented in model diagrams in Figure 1. The chord length of the airfoils is 0.2 m and the wind turbine is counterclockwise. The azimuth angle of the initial position is 0°.

Figure 1.

Schematic diagram of the two types of airfoils.

Calculation domain settings

The vertical axis wind turbine is numerically simulated using a two-dimensional computational model and the computational domain is schematically represented in Figure 2. The rotating shaft and the support rod, which have little bearing in the calculation of the results are disregarded in the calculation. The computational domain is divided the entire into a 10D by 15D rectangular area (Li et al., 2022; Maalouly et al., 2022). The overall calculation domain is divided into two parts- the stationary domain and the rotating domain. The boundary condition is established as the intersection of the stationary domain and rotating domain. The calculation domain left boundary is set as a velocity inlet, while the right boundary is set as a pressure outlet, and the upper and lower boundary is set as no-slip walls. The rotation center is 5D away from the left velocity inlet and 10D away from the right pressure outlet. The inlet wind speed is set to 7, 8, and 9 m/s at three different wind environment conditions. The blade position shown in Figure 2 is the starting position.

Figure 2.

Two-dimensional schematic of the computational domain.

Mesh independence verification

The mesh division makes up a significant portion of the preprocessing cycle, and the mesh quality has a significant impact on the outcomes and accuracy of the computations. So a structured mesh with higher accuracy is used for meshing. Figure 3 shows the mesh of the computational domain when the azimuth angle of the DU97-W-300 airfoil is 0°.

Figure 3.

DU97-W-300 airfoils computational domain mesh.

The wind energy utilization value is verified at three different mesh numbers in the case of an incoming wind speed of 8 m/s, keeping the same TSR (Tip Speed Ratio), and choosing a 0° azimuth angle. The calculation results are shown in Table 2, where N stands for the number of mesh, ρ for the air density, λ, and TSR for the tip speed ratio, C_p for the utilization rate of wind energy, Q for the torque, ω for the angular velocity of the wind turbine, M for the torque coefficient, and L for the characteristic length.

Table 2.

Mesh independent verification results.

N	λ	C_p
423,193	1.5	0.36602
586,570	1.5	0.36800
819,661	1.5	0.37038

From Table 2, it can be seen that the mesh density has little effect on the calculation results, and the medium-density mesh is selected for the calculation.

Q = \frac{M ρ V^{2} S L}{2}

(1)

ω = λ V

(2)

C_{p} = \frac{Q ω}{2 ρ {D h V}_{\infty}^{3}}

(3)

Calculation model parameter setting

The efficiency of the simulation and the accuracy of the results are connected to the choice of time step in a two-dimensional simulation of the study model. Theoretically, the smaller the time step, the higher the calculation accuracy. The time steps commonly correspond to the time of 1° and 2° azimuth angles rotation of the wind turbine (Aihara et al., 2022; Hassanpour and Azadani, 2021; Kooiman and Tullis, 2010). At the same time, the results of the calculation of the two time steps show a negligible deviation, with blade rotation 1° used time Δ t = 0.00087 second. Figure 4 depicts the fluctuation in TSR and the utilization rate of wind energy for the model with airfoils DU97-W-300 at 8 m/s wind speed at two time steps. TS in the Figure 4 represents the time step. So blades are set to be calculated once every 2° of rotation to reduce calculation costs.

Δ t = \frac{1}{3 n} = 0.00174 s

(4)

Figure 4.

Variation of the average coefficient of power with the TSR at two time steps.

Turbulence model and solvers

When the flow field near the airfoils is complex, the Transition-SST turbulence model can more accurately respond to the macroscopic flow phenomenon (Castelli et al., 2011; Moreno-Armendáriz et al., 2021; Peng et al., 2020; Sepehrianazar et al., 2019; Wu et al., 2022). Therefore, the turbulence model is chosen as the Transition-SST. To improve the computational stability, the SIMPL algorithm is used for pressure and velocity coupling. The second-order windward format is used for the momentum, turbulent kinetic energy, and turbulent dissipation rate. The hydraulic diameter is set to D_H = 0.2 m, the same value as the characteristic length. The turbulence intensity is calculated as shown in formulas (5), and (6).

I = 0.16 \cdot {R e}^{- \frac{1}{8}}

(5)

R e = \frac{ρ \cdot V \cdot D_{H}}{μ}

(6)

I stands for the intensity of the turbulence, Re for the Reynolds number, ρ for air density, V for fluid velocity, and μ for air viscosity. I = 3.8% is computed to specify the values of the quantum boundary, such as the hydraulic diameter and the turbulence intensity, on the flow field border at an air speed of 8 m/s.

Computational data processing and analysis

The efficiency of the models with symmetric and asymmetric airfoils with various tip speed ratios at various wind speeds (7, 8, and 9 m/s) is examined. Which is analyzed from the perspectives of wind energy utilization, velocity contours, and vorticity contours.

Single-blade comparison of wind energy utilization

Figure 5 gives a comparison of the C_p of models with symmetrical and asymmetrical airfoils with different tip speed ratios at 8 m/s operating conditions. The specific method is to observe the variation in the utilization rate of wind energy (coefficient of power) of a single blade with turning angles.

Figure 5.

Variation of the coefficient of power with azimuth angle for wind turbines with two types of airfoils: (a) λ = 1.0, (b) λ = 1.5, (c) λ = 2.0, (d) λ = 2.5, and (e) λ = 3.0.

From Figure 5, it can be seen when the single blade rotates to 90 degrees, the wind energy utilization rate of both wind turbines with two types of airfoils reach their peaks. The peak of the C_p (utilization rate of wind energy or the average coefficient of power) of the wind turbine with airfoils DU97-W-300 is higher than the wind turbine with airfoils NACA0021 by 84.8% when the λ = 1.0. The wind turbine with symmetric airfoils NACA0021 experiences more severe blade stall phenomena under low tip speed ratio situations than the wind turbine with asymmetric airfoils DU97-W-300. By monitoring the pressure coefficient on the blades and calculating C_p according to formulas (1), (2), and (3), it is observed that the pressure coefficient on the blades of the asymmetric airfoils DU97-W-300 is significantly greater than that of the symmetric airfoils NACA0021. The pressure differences of the wind turbine’s blades with airfoils DU97-W-300 are greater than that of the wind turbine’s blades with airfoils NACA0021, resulting in a higher kinetic energy generation. Accordingly, the C_p of the wind turbine with asymmetric airfoils DU97-W-300 is significantly better than the wind turbine with symmetric airfoils NACA0021. When the λ = 1.5, the wind turbine with airfoils DU97-W-300 blades’ absorption of wind energy capacity is stronger than the wind turbine with airfoils NACA0021. The wind turbine with asymmetric DU97-W-300 utilizes wind energy slightly better than the wind turbine with symmetric airfoils NACA0021, however, the difference is lessened. This phenomenon can also be seen in the velocity contours (Figure 8(c) and (d)). The two types of airfoils almost utilize the same amount of wind energy when the λ = 2.0 and the peaks almost line up. As the TSR rises, unlike the case at the low TSRs, the C_p of the wind turbine with symmetric airfoils NACA0021 begins to be superior to that of asymmetric airfoils DU97-W-300. When the λ = 2.5, the wind turbine with airfoils NACA0021 blades’ absorption of wind energy capacity is stronger than the wind turbine with airfoils DU97-W-300. The wind turbine with symmetrical airfoils NACA0021 has a 4.9% higher peak of the C_p than the wind turbine with DU97-W-300 airfoils. This result is also verified in Figure 9(c) and (d) later in the paper. When the tip speed ratio rises to 3.0, the C_p of the wind turbine with symmetric airfoils NACA0021 is better than the wind turbine with asymmetric airfoils DU97-W-300, and the value difference increases, and the peak value is higher than that of the wind turbine with airfoils DU97-W-300 by 18.0%. The aerodynamic performance of the experimental model with symmetric airfoils NACA0021 is more outstanding than the wind turbine with airfoils DU97-W-300.

3-blade comparison wind energy utilization

Figure 6 gives a comparison of the aerodynamic characteristics of the model with symmetrical and asymmetrical airfoils with different tip speed ratios at 8 m/s operating conditions. The specific method is observing the variation in the utilization rate of wind energy (coefficient of power) of the three blades with turning angles.

Figure 6.

Variation of the coefficient of power with azimuth angle for wind turbines with two types of airfoils: (a) λ = 1.0, (b) λ = 1.5, (c) λ = 2.0, (d) λ = 2.5, and (e) λ = 3.0.

From Figure 6, it can be seen that the wind turbine’s blades with two types of airfoils rotate to 60° achieved their maximum level. Additionally, the rotation period is 120 degrees due to the three blades. When the λ = 1.0, The C_p of the wind turbine with asymmetric airfoils DU97-W-300 is significantly better than that of symmetric airfoil NACA0021. The peak of the C_p of the wind turbine with airfoils DU97-W-300 is higher than the wind turbine with airfoils NACA0021 by 95.8%. When the λ = 1.5, the wind turbine with asymmetric airfoils DU97-W-300 utilizes wind energy slightly better than the wind turbine with symmetric airfoils NACA0021, however, the difference is lessened. The two wind turbines almost utilize the same amount of wind energy when the λ = 2.0 and the peaks almost line up. As the TSR rises, unlike the case at the low TSRs, the C_p of the wind turbine with symmetric airfoils NACA0021 begins to be superior to that of the wind turbine with asymmetric airfoils DU97-W-300. When the λ = 2.5, the wind turbine with symmetrical airfoils NACA0021 has a 4.9% higher peak of the C_p than the wind turbine with airfoils DU97-W-300. When the tip speed ratio rises to 3.0, the C_p of the experimental model with symmetric airfoils NACA0021 is better than the wind turbine with asymmetric airfoils DU97-W-300, and the value difference increases. The peak value is higher than that of the wind turbine with airfoils DU97-W-300 by 8.3%, and the aerodynamic performance of the experimental model with symmetric airfoils NACA0021 is better than that of the wind turbine with airfoils DU97-W-300.

Overall, the outcomes agree with the findings from the paper’s earlier discussion of a single blade’s monitoring. The wind speed energy loss surrounding the symmetric airfoils NACA0021 blades is less under low tip speed ratio conditions. This suggests that the blades have the poor wind catching capabilities and smaller pressure differences on the blades, which leads to a lower aerodynamic performance than the wind turbine with asymmetric airfoils DU97-W-300. On the other hand, the opposite phenomena start to appear when the tip speed ratio rises. The wind turbine with symmetric airfoils NACA0021 steadily outperforms the wind turbine with asymmetric airfoils DU97-W-300 in terms of aerodynamic performance when the tip speed ratio rises over 2.0. The vorticity contours are showed in Figures 10 and 11, which are covered later in the paper, support the results of the experiment even more.

To avoid limitations and peculiarities, two more different wind environments (7 m/s, 9 m/s) are selected for the wind speed of 8 m/s. The average of the moment coefficients of 20 cycles after convergence in the wind turbine simulation results is taken to find the C_p of the model. Figure 7 shows the C_p of the wind turbine with symmetric airfoils NACA0021 and the wind turbine with asymmetric airfoils DU97-W-300 at different wind speeds and multiple tip speed ratios.

Figure 7.

Variation of the average coefficient of power with TSR for wind turbines with two types of airfoils: (a) v = 7 m/s, (b) v = 8 m/s, (c) v = 9 m/s.

Figure 7 demonstrates that the trend of the C_p curves for the two models at multiple TSRs is essentially the same. When a wind turbine is working at a low-speed condition (low TSRs ), its C_p is lower. Because most of the blades are in a stall and less aerodynamic force is produced while the wind turbine works at low speed, it has poor aerodynamic properties. Because the local airflow of the wind turbine is damaged at high speeds, causing poor aerodynamic properties of the wind turbine, the wind turbine’s C_p falls with increasing speed when the wind turbine works at high speeds ( high TSRs ). The wind turbine has good aerodynamic performance when it works at its best, and C_p achieves its maximum value.

As shown in Figure 7, it can be interpreted when the tip speed ratio λ = 1.0, λ = 1.5, the C_p of the experimental model with airfoils DU97-W-300 is higher than the wind turbine with airfoils NACA0021 at all three wind speeds. The aerodynamic characteristic of the model with airfoils DU97-W-300 is relatively better. On the contrary, when λ = 2.0, λ = 2.5, λ = 3.0, the aerodynamic characteristic of the model with airfoils NACA0021 at all three wind speeds is higher than that of the wind turbine with airfoils DU97-W-300 at three wind speeds. This indicates that the wind turbine with airfoils DU97-W-300 aerodynamic properties is outstanding in low-speed conditions and appropriate for low-wind speed areas. The model with airfoils NACA0021 has good high-speed aerodynamics, which is appropriate for locations with high wind speed conditions.

Velocity contours and vorticity contours

In the three wind speed conditions, v=7m/s, v=8m/s, and v=9m/s, the tip speed ratios λ = 1.5 and λ = 2.5 are used to construct the velocity contours around the airfoils for the wind turbine with symmetric airfoils NACA0021. The wind turbine with asymmetric airfoils DU97-W-300 is illustrated in Figures 8 and 9.

Figure 8.

Velocity contours around two types of airfoils blades at three wind speeds for TSR = 1.5: (a) NACA0021 (v = 7 m/s), (b) DU97-W-300 (v = 7 m/s), (c) NACA0021 (v = 8 m/s), (d) DU97-W-300 (v = 8 m/s), (e) NACA0021 (v = 9 m/s), and (f) DU97-W-300 (v = 9 m/s).

Figure 9.

Velocity contours around two types of airfoils blades at three wind speeds for TSR = 2.5: (a) NACA0021 (v = 7 m/s), (b) DU97-W-300 (v = 7 m/s), (c) NACA0021 (v = 8 m/s), (d) DU97-W-300 (v = 8 m/s), (e) NACA0021 (v = 9 m/s), and (f) DU97-W-300 (v = 9 m/s).

Figure 8 can be seen in the tip speed ratio λ = 1.5, three kinds of incoming wind speeds, the wind turbine with asymmetric airfoils DU97-W-300′s blades upwind speed are higher than the wind turbine with symmetric airfoils NACA0021. The wind turbine with asymmetric airfoils DU97-W-300 by the color of the speed size of the wakes compare to the wind turbine with airfoils NACA0021 is more obvious, indicating that in the λ = 1.5. The experimental model with airfoils DU97-W-300 has greater energy loss at the wake, so its blades' absorption of wind energy capacity is stronger than the wind turbine with airfoils NACA0021. Analysis of Figure 9 reveals that the tip speed ratio λ = 2.5 and λ = 1.5 show the opposite trend. The wind turbine with symmetric airfoils NACA0021′s blades' windward speed is higher than the wind turbine with asymmetric airfoils DU97-W-300. In general, the wind turbine with airfoils DU97-W-300 can capture more wind energy than the wind turbine with airfoils NACA0021 in the windward zone at the low TSRs, whereas the wind turbine with airfoils NACA0021 can do so in the windward region at high tip speed ratio.

As shown in Figures 10 and 11, the tip speed ratio λ = 1.5 and λ = 2.5 are selected to make the vorticity contours around the wind turbine with symmetric airfoils NACA0021 and the wind turbine with asymmetric airfoils DU97-W-300 at the incoming wind speed v=8/s per 30° rotation of the airfoils.

Figure 10.

Vorticity contours of two types of airfoils at different azimuth angles for TSR = 1.5: (a) NACA0021 (Azimuth Angle = 0°), (b) DU97-W-300 (Azimuth Angle = 0°), (c) NACA0021 (Azimuth Angle = 30°), (d) DU97-W-300 (Azimuth Angle = 30°), (e) NACA0021 (Azimuth Angle = 60°), (f) DU97-W-300 (Azimuth Angle = 60°), (g) NACA0021 (Azimuth Angle = 90°), and (h) DU97-W-300 (Azimuth Angle = 90°).

Figure 11.

Vorticity contours of two types of airfoils at different azimuth angles for TSR = 2.5: (a) NACA0021 (Azimuth Angle = 0°), (b) DU97-W-300 (Azimuth Angle = 0°), (c) NACA0021 (Azimuth Angle = 30°), (d) DU97-W-300 (Azimuth Angle = 30°), (e) NACA0021 (Azimuth Angle = 60°), (f) DU97-W-300 (Azimuth Angle = 60°), (g) NACA0021 (Azimuth Angle = 90°), and (h) DU97-W-300 (Azimuth Angle = 90°).

Analysis of Figure 10 reveals that the vortex situation between the wind turbine with airfoils DU97-W-300′s blades is better than the model with airfoils NACA0021 at the λ = 1.5. The interaction between blades is lower, and the aerodynamic performance of the experimental model with airfoils DU97-W-300 is better than that of the wind turbine with airfoils NACA0021. Meanwhile, this result is also corroborated by the wind energy utilization shown per 30° rotation of a single blade as shown in Figure 5(b), which is in the previous part of the paper. From Figure 11, it can be interpreted that the interaction between the wind turbine with airfoils NACA0021′s blades is less than that of the wind turbine with airfoils DU97-W-300. It is also consistent with the phenomenon presented in Figure 5(d). It is revealed that the aerodynamic performance of the wind turbine with airfoils NACA0021 is more outstanding than the wind turbine with airfoils DU97-W-300 at the λ = 2.5.

Conclusion

The aerodynamic characteristics of two types of airfoils for vertical axis wind turbines are compared and analyzed in detail using computational fluid dynamics (CFD) in this paper. The utilization rate of wind energy of the vertical axis wind turbines with symmetrical and asymmetrical airfoils is investigated. Single-blade, 3-blade, different tip speed ratios, and three wind speeds (7, 8, 9 m/s) are set as the parameters. Then it is further analyzed by observing velocity contours and vorticity contours. It is concluded that the aerodynamic performance of the wind turbine with asymmetric airfoils DU97-W-300 is better than the wind turbine with symmetric airfoils NACA0021 when the vertical axis wind turbines are operated at the low TSRs. On the contrary, the aerodynamic performance of the wind turbine with symmetric airfoils NACA0021 is better at high TSRs. Therefore, the wind turbine with asymmetric airfoils DU97-W-300 is suitable for low wind speed environments, while the wind turbine with symmetric airfoils NACA0018 is appropriate for locations with high wind speed conditions.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work is supported by Foundation of Jiangxi Educational Committee, China (grant number GJJ200822), Doctor Foundation of Jiangxi University of Science and Technology, China (grant number 205200100513).

ORCID iD

Haipeng Wang

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