The main purpose of the upcoming article is to investigate the effects of using a blade with two NACA 0015 airfoils with a geometric ratio of 0.5 on the output power of a vertical-axis wind turbine exposed to wind with a constant speed of 10 m/s at different rotational speeds. Initially, creating a suitable strategy for the numerical simulation of a straight-blade vertical axis wind turbine using a 2D mesh has been discussed. This 2D simulation was done via Ansys 2021 commercial software and results were verified with experimental results. Appropriate settings have been used to solve the issue of not modeling the airfoil edge vortices in a 2D simulation and minimizing its effects. Although in addition to the errors of a 2D modeling, the Reynolds-averaged Navier-Stokes (RANS) solvers have errors compared to the Direct Numerical Simulation method, however different settings and modeling have been used to extract closest results to experimental data. Additionally, the sliding mesh technique has been utilized, which provides lower computational cost than the dynamic mesh technique. The result of this numerical solution has 90% accuracy relative to simulation using SST K-ω model. Following, based on the validated results and using similar settings, the effects of using double-airfoils in two different modes have been investigated and the results have been compared with the single airfoil turbine. Ultimately, the power coefficient at variable rotational speeds has been evaluated for single and double-airfoil turbines, which indicates the power coefficient of the turbine has increased by 12% on average.

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