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Wind and Structures Volume 42, Number 3, March 2026 , pages 329-355 DOI: https://doi.org/10.12989/was.2026.42.3.329 |
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Numerical analysis of unsteady performance of an aerofoil with surface openings under Darrieus motion |
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Yunus Celik, Derek Ingham, Lin Ma, Burhan Necati Kiziloglu, Mohamed Pourkashanian
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| Abstract | ||
| The aerodynamic behavior of vertical-axis wind turbines (VAWTs), particularly the H-type Darrieus configuration, remains central to renewable energy research due to persistent challenges in self-starting and efficiency at low tip speed ratios (TSRs). This study presents a numerical investigation of a modified NACA0018 aerofoil with chordwise surface openings, termed a J-shaped aerofoil, operating under Darrieus motion. Two-dimensional CFD simulations in ANSYS Fluent evaluated opening ratios of 30%, 60%, and 90% of chord length, focusing on lift, drag, and chordwise force coefficients during dynamic stall. A validated oscillating aerofoil model with user-defined pitching replicated Darrieus kinematics, with systematic variation of TSR and pitch angle. Results show that larger openings enhance lift and delay stall onset in the positive angle of attack phase, improving self-starting potential. However, these gains are offset by increased drag and reduced performance during the negative phase, particularly downstream. The J-shaped aerofoil with 90% opening achieved ~30% higher peak lift than the conventional profile, with improved flow reattachment and vortex dynamics observed. Despite elevated downstream losses, the enhanced upstream torque indicates a net advantage for turbine start-up capability. These findings provide insight for optimizing blade design in low-Reynolds-number VAWTs, balancing self-starting improvement against efficiency at higher TSRs. | ||
| Key Words | ||
| aerodynamics; Computational Fluid Dynamics (CFD); darrieus motion; dynamic stall; j-shaped aerofoil; self-starting | ||
| Address | ||
| Yunus Celik:1)Energy2050, Department of Mechanical Engineering, Faculty of Engineering, University of Sheffield, Western Bank S10 2TN, Sheffield, United Kingdom 2)Department of Aeronautical Engineering, Sivas University of Science and Technology, Gültepe Mahallesi 58000, Sivas, Turkey Derek Ingham:Energy2050, Department of Mechanical Engineering, Faculty of Engineering, University of Sheffield, Western Bank S10 2TN, Sheffield, United Kingdom Lin Ma:Energy2050, Department of Mechanical Engineering, Faculty of Engineering, University of Sheffield, Western Bank S10 2TN, Sheffield, United Kingdom Burhan Necati Kiziloglu:Department of Aeronautical Engineering, Sivas University of Science and Technology, Gültepe Mahallesi 58000, Sivas, Turkey Mohamed Pourkashanian:Energy2050, Department of Mechanical Engineering, Faculty of Engineering, University of Sheffield, Western Bank S10 2TN, Sheffield, United Kingdom | ||