This paper presents a numerical study of the optimization of the geometric parameters of a four-bladed Darrieus vertical-axis wind turbine (VAWT) with a NACA 0021 aerodynamic profile. The aim of the study was to increase the aerodynamic efficiency of the turbine by selecting optimal values of the rotor diameter and blade chord length. The Taguchi method using an orthogonal array was used as an optimization method, which reduced the number of necessary calculations from 77 to 20 while maintaining the reliability of the analysis. CFD modelling was performed in the ANSYS 2022 R2 Fluent software environment based on a two-dimensional non-stationary model, including a full rotor revolution and an analysis of the steady-state mode for the twentieth cycle. As a result of the analysis, the optimal parameters were determined: rotor diameter D = 3 m and chord length c = 0.4 m. Additionally, for the selected configuration, the numerical model was validated by constructing the dependence of the power coefficient Cp on the tip speed ratio λ in the range from 0.2 to 2.8. The maximum value of Cp was 0.35 at λ = 2.2, which is an increase of ~64% compared to the least efficient rotation mode in the considered range of λ. The obtained results allow us to conclude that the Taguchi method can be used in combination with CFD modelling for fast and accurate optimization of the aerodynamic parameters of low-power wind turbines.

In this study, we conducted experimental and numerical investigations of a Darrieus rotor with asymmetrical blades, which has two structural configurations—with and without horizontal parallel plates. Experimental tests were conducted in a wind tunnel at various air flow velocities (ranging from 3 m/s to 15 m/s), measuring rotor rotation frequency, torque, and thrust force. The computational simulation used the ANSYS 2022 R2 Fluent software package, where CFD simulations of air flow around both rotor configurations were performed. The calculations employed the Realizable k-ε turbulence model, while an unstructured mesh with local refinement in the blade–flow interaction zones was used for grid generation. The study results showed that the rotor with horizontal parallel plates exhibits higher aerodynamic efficiency at low wind velocities compared to the no-plates rotor. The experimental findings indicated that at wind speeds of 3–6 m/s, the rotor with plates demonstrates 18–22% higher torque, which facilitates the self-start process and stabilizes turbine operation. The numerical simulations confirmed that horizontal plates contribute to stabilizing the air flow by reducing the intensity of vortex structures behind the blades, thereby decreasing aerodynamic drag and minimizing energy losses. It was also found that the presence of plates creates a directed flow effect, increasing the lift force on the blades and improving the power coefficient (Cp). In the case of the rotor without plates, the CFD simulations identified significant low-pressure zones and high turbulence regions behind the blades, leading to increased aerodynamic losses and reduced efficiency. Thus, the experimental and numerical modeling results confirm that the Darrieus rotor with horizontal parallel plates is a more efficient solution for operation under low and variable wind conditions. The optimized design with plates ensures more stable flow, reduces energy losses, and increases the turbine’s power coefficient. These findings may be useful for designing small-scale wind energy systems intended for areas with low wind speeds.

This paper presents the results of wind tunnel experiments, where lift and drag coefficients were studied at various angles of attack and flow speeds, alongside numerical simulations conducted in ANSYS. The main objectives of this study are to investigate the aerodynamic characteristics and self-starting capabilities of three-bladed Darrieus rotors with asymmetrical blades and assess their efficiency. This study presents results on pressure distribution, velocity contours, and the impact of the angle of attack on pressure and aerodynamic characteristics. The results show that blades with asymmetric shapes achieve maximum values of lift and drag coefficients at angles of attack between 180° and 210°, with peak coefficients of Cx = 1.38 and Cy = 2.84, respectively. These findings indicate high effectiveness of the blades at low wind speeds, making them promising for use in WEIs where good starting characteristics and high power output are especially important. A good correlation was found between experimental data and numerical simulation results. This study contributes to the development of recommendations for optimizing the design and operating parameters of wind-driven powerplants, which in turn can improve their reliability and economic efficiency. Thus, the paper aims to expand the knowledge in the field of wind power engineering and to develop technologies to facilitate a wider adoption of wind-driven powerplants in the energy infrastructure of different regions.

This paper presents a comprehensive experimental and numerical investigation of the aerodynamics of a vertical-axis Darrieus wind turbine equipped with newly developed modified asymmetric blades intended to enhance performance at low and variable wind speeds. Using URANS modeling (SST k–ω) combined with full-scale testing, a detailed comparison was carried out against the classical NACA 0021 airfoil. The results show that the asymmetric profile increases starting torque by 30–40%, reduces negative torque by 20–25%, and decreases load pulsations by 15–20%, owing to the delayed onset of dynamic stall and the stabilization of the vortex wake structure. Within the optimal operating range of TSR = 2.5–4, an 18–22% increase in pressure differential is observed, resulting in a higher power coefficient; the maximum Cp reaches 0.15, exceeding that of the symmetric configuration by 20–25%. The agreement between CFD predictions and experimental measurements exceeds 95%, confirming the robustness of the numerical model employed. The findings clearly demonstrate the substantial effectiveness of the proposed blade geometry and its strong potential for next-generation VAWTs optimized for regions with low wind resources.

The purpose of this work is to study the fields of average values of velocity in a turbulent air jet propagating along a smooth cylindrical surface with an adjustable nozzle width being b, the curvature parameter SR and Re number on both convex and concave surfaces. To identify basic patterns of physical phenomena occurring in the boundary layer, it has been established that in universal coordinates, the wall velocity profiles have a universal nature in the region of a change in the curvature parameter 0 ⩽ S_R ⩽ |±0.12|, and virtually coincide with the velocity profiles of a turbulent boundary layer on a flat plate in a uniform flow past, except for the velocity peak region. This is due to the fact that the longitudinal pressure gradient is 104 ÷ 105 times lower than transverse pressure gradient. According to our data, it has been established that the excess static pressure near the streamlined surface with a distance from the nozzle and an increase in jet thickness can reach up to 30–40% of the velocity head.

It is shown that the aerodynamics of turbulent jets flowing from rectangular nozzles is significantly influenced not only by the presence or absence of limiting end walls, but also by the development of large-scale coherent vortices formed at the initial section of the jet. It is established that in the case of large-scale vortices formed at the initial section with axes parallel to the free edge of the nozzle, they can either rest against the end walls with their ends, or close on themselves at the end walls, covering the initial section of the jet. It is shown that the initially formed annular vortices covering the initial section of the jet deform as they move away from the nozzle and turn into vortex cords with axes parallel to the direction of the jet. As a rule, the vortex cords are arranged symmetrically relative to the axis and have opposite directions. These vortices are the main cause of the appearance of an uneven velocity and temperature profile along the axis. At the same time, large-scale primary vortices with their ends rest against the end walls and cannot cause the appearance of maxima and minima of the velocity profile along the axis. In this case, the development of the boundary layers at the end walls is similar to the development of the boundary layer of a homogeneous flow in a flat channel.