A NUMERICAL STUDY OF THE AERODYNAMIC PERFORMANCE OF A FOUR-BLADE SAVONIUS VERTICAL-AXIS WIND TURBINE

Abstract

This paper presents a comprehensive numerical study of a four-bladed Savonius-type vertical-axis wind turbine (VAWT) using ANSYS CFX. The objective was to numerically evaluate transient aerodynamics, torque characteristics, and the power coefficient (Cp) under well-controlled computational conditions, as well as to systematize best practices from current literature regarding high-accuracy yet computationally efficient modeling. The simulation involved a rotating rotor domain embedded within a stationary stator domain, with a Transient Rotor–Stator (TRS) frame change interface applied between them. The inlet wind speed was set to 7 m/s with a turbulence intensity of 5%. The rotor rotated around the global Z-axis with an angular velocity of –90 rad/s. For industrial flows, the standard k–ε turbulence model with scalable wall functions was chosen due to its stability and compatibility with wall treatments. Mesh generation employed an inflation-based refinement strategy near blade surfaces, resulting in approximately 1.0 million nodes and 5.8 million elements, with maximum element skewness kept below 0.8. The results revealed periodic oscillations of pressure and velocity on the blade surface, coherent vortex shedding, and wake–flow interactions. Compared to three-bladed configurations, qualitative trends indicated smoother torque transfer, although the peak Cp value appeared slightly lower. Such a trade-off has also been noted in previous studies [1–3]. The study consolidated modeling choices, verification procedures, and data reduction methods, providing a reproducible guideline for subsequent optimization research.