## 3 Results and Discussions  
### Analysis of Velocity, Pressure and Torque Fields  
Based on the numerical simulation, a comprehensive assessment of the influence of the blade chord length on the aerodynamic behavior of the [PERSON] vertical-axis wind turbine was performed for different rotor diameters. The analysis included visualization of the velocity fields (Figure 7) and pressure (Figure 8), as well as an assessment of the change in the torque coefficient depending on the rotor rotation angle for the last, twentieth revolution (Figures 9-13). The results are presented below, reflecting the flow characteristics, the nature of load distribution, and the dynamics of the generated torque coefficient for different values of the chord length and rotor diameter. \begin{table}
\begin{tabular}{c c c} \hline
**Test No.** & **Rotor Diameter D, m** & **Chord Length c, m** \\ \hline  
\end{tabular}
\end{table} 
Table 5: Orthogonal array L20 for two factors: rotor diameter (D) and chord length (c). Figure 7: Cont. Figure 7: _Cont._  
Figure 7a-e show the velocity fields reflecting the effect of changing the rotor diameter (D = 1.5-4 m) and blade chord length (c = 0.2-0.8 m) on the flow structure around the [PERSON] wind turbine. At smaller diameters (D = 1.5-2.25 m), the flow is characterized by pronounced circulation and local acceleration zones, especially at chords of 0.4 and 0.6 m, which indicates favorable torque generation. With an increase in D to 3-4 m, the flow becomes more uniform and \"clean\", but the intensity of the accelerated zones decreases, which may indicate a drop in local pressure gradients and a decrease in the beneficial interaction between the flow and the blades. At c = 0.2 m, pronounced turbulence and flow separation are observed, and at c = 0.8 m, signs of rotor overload are observed, accompanied by a slowdown behind the blades and an increase in drag. The most stable and balanced flow with optimal energy concentration is observed at c = 0.4-0.6 m, regardless of the diameter, which confirms the universality of these values for the efficient operation of the wind turbine under the given conditions. Figure 8a-e show the static pressure distribution fields for different combinations of the rotor diameter (from D = 1.5 m to D = 4.0 m) and chord length (from c = 0.2 m to c = 0.8 m). The analysis showed that at small diameters (D = 1.5-2.25 m), more pronounced pressure gradients are observed on the blade surface, especially at c = 0.4-0.6 m, which indicates active lift formation and effective interaction of the flow with the profile. As the diameter increases to D = 3-4 m, the pressure field becomes more uniform, the oscillation amplitude decreases, and the high- and low-pressure zones become less contrasting, which may indicate a decrease in the aerodynamic load and, as a consequence, a drop in efficiency. At c = 0.2 m, sharp local pressure jumps are recorded in all cases, which can lead to vibrations and unstable operation. At c = 0.8 m, the pressure at the inlet edge increases, the resistance increases, especially at small D. The most balanced and uniform pressure  
Figure 7: Contour of distribution of flow velocity field through a vertical wind turbine with four blades for all combinations considered: (**a**) D  
distribution is observed at c = 0.4-0.6 m for all diameters, which confirms the optimality of these chord values in the conditions of the range under study. Figure 8: _Cont_.