Numerical Investigation of Elliptical Deflectors with Different Aspect Ratios on Aerodynamic Performance of a Savonius Wind Turbine

Document Type : Original Article

Authors
Milad Mehrpooya 1
Mohammad javad Maghrebi 2
1 M.S., Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
2 Professor, Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
10.22034/stme.2025.549288.1172
Abstract
Savonius wind turbines are attractive for small-scale wind energy applications because of their simple structure and ability to operate at low wind speeds. However, their aerodynamic efficiency is relatively low, mainly due to the negative torque generated by the returning blade. In this study, the effect of an elliptical supporting rod with different aspect ratios on the aerodynamic performance of a Savonius wind turbine was numerically investigated. Two-dimensional transient simulations were performed using ANSYS Fluent and the SST k–ω turbulence model. The numerical model was validated against available experimental data. Several elliptical aspect ratios and tip-speed ratios (TSRs) were considered, and the power coefficient was used as the main performance indicator. The results showed that elliptical supporting rods with aspect ratios greater than one generally improved turbine performance. The maximum improvement was obtained at an aspect ratio of 1.2, reaching approximately 24% compared with the reference configuration. The improvement became more significant at higher TSRs. However, increasing the aspect ratio beyond 1.3 reduced the performance because the supporting rod increasingly obstructed the incoming flow toward the advancing blade. The results demonstrate that optimizing the aspect ratio of the supporting rod can provide an effective approach for improving Savonius turbine performance.
Keywords
Savonius Wind Elliptical
Supporting RodSupporting Rod
Tip Speed Ratio
Aspect Ratio
Power Coefficient
Subjects
[1] M. Yadegari and M. Ghassemi, “Investigation of the effects of temperature, mass flow rate of the injected fuel, pore diameter, porosity and ambient pressure on the amount of pollutants in the combustion chamber,” Iranian Journal of Mechanical Engineering Transactions of the ISME, Vol. 23, No. 1, pp. 122–146, 2022, DOI: 10.30506/jmee.2022.547922.1282. (in Persian)
[2] R. Abbaspour, M. Yadegari, and A. B. Khoshnevis, “Effect of airfoil’s attack angle and airfoil-cylinder configuration on turbulence parameters and airfoil’s aerodynamic efficiency,” Energy Science & Engineering, Vol. 13, No. 11, pp. 5432–5450, 2025, DOI: 10.1002/ese3.70250. (in Persian)
[3] R. Abbaspour, M. Yadegari, A. B. Khoshnevis, and D. Hoseinzade, “Optimization of horizontal spacing in cylinder-NACA0012 airfoil configuration in the Sharrow propeller using entropy generation analysis and multi-objective genetic algorithm,” Journal of Marine Science and Technology, Vol. 30, No. 4, pp. 909–938, 2025, DOI: 10.1007/s00773-025-01097-5. (in Persian)
[4] A. Kalantari, “Energy and exergy assessment of a novel combined geothermal-LNG cycle with energy recovery and green hydrogen production,” Science and Technology in Mechanical Engineering, Vol. 4, No. 1, pp. 217–235, 2025, DOI: 10.22034/stme.2025.528631.1135. (in Persian)
[5] D. E. H. J. Gernaat, H. S. de Boer, V. Daioglou, S. G. Yalew, C. Müller, and D. P. van Vuuren, “Climate change impacts on renewable energy supply,” Nature Climate Change, Vol. 11, No. 2, pp. 119–125, 2021, DOI: 10.1038/s41558-020-00949-9.
[6] A. Kalantari and M. Soltani, “Performance evaluation of renewable energy systems for green hydrogen production in Southern Iran: A case study of Qeshm Island,” Journal of Sustainable Energy Systems, Vol. 5, No. 1, pp. 143–164, 2026, DOI: 10.22059/ses.2025.397990.1165. (in Persian)
[7] A. Kalantari, P. Rezagholikhani, and N. Hajialigol, “Energy and exergy analysis of a novel multi-generation system based on biomass gasification for the simultaneous production of electricity, fresh water, heat, and hydrogen,” Energy Engineering and Management, Vol. 14, No. 4, pp. 36–51, 2025, DOI: 10.22052/eem.2025.257322.1134. (in Persian)
[8] A. Pallotta, D. Pietrogiacomi, and G. P. Romano, “HYBRI—A combined Savonius-Darrieus wind turbine: Performances and flow fields,” Energy, Vol. 191, Art. no. 116433, 2020, DOI: 10.1016/j.energy.2019.116433.
[9] A. Kalantari, M. Mehrpooya, A. Pourmand, and M. Soltani, “Thermodynamic evaluation of a biomass-based combined cooling, heating, and power (CCHP) system with a high-performance absorption chiller and hot-box for building application,” Journal of Applied and Computational Sciences in Mechanics, 2025, DOI: 10.22067/jacsm.2025.94113.1339. (in Persian)
[10] A. Kalantari and N. Hajialigol, “Analysis of a biomass-fueled combined heat, power, and cooling system featuring innovative heat recovery and a triple organic Rankine cycle,” Fuel and Combustion, Vol. 18, No. 2, pp. 1–30, 2025, DOI: 10.22034/jfnc.2025.535934.1431. (in Persian)
[11] A. P. Schaffarczyk, Wind Power Technology: An Introduction, 2nd ed. Cham, Switzerland: Springer, 2023, DOI: 10.1007/978-3-031-20332-9.
[12] V. Ballestín-Bernad, J. S. Artal-Sevil, J. A. Domínguez-Navarro, and J. L. Bernal-Agustín, “Low-cost variable-speed wind turbines design by recycling small electrical machines: Arrangement of permanent magnets in the rotor,” Renewable Energy and Power Quality Journal, Vol. 20, pp. 833–838, 2022, DOI: 10.24084/repqj20.450.
[13] M. Ebrahimpour, R. Shafaghat, R. Alamian, and M. Safdari Shadloo, “Numerical investigation of the Savonius vertical axis wind turbine and evaluation of the effect of the overlap parameter in both horizontal and vertical directions on its performance,” Symmetry, Vol. 11, No. 6, Art. no. 821, 2019, DOI: 10.3390/sym11060821. (in Persian)
[14] M. Mehrpooya and A. Kalantari, “A review investigation of the Savonius hydrokinetic turbines: Application and optimization,” Sustainable Energy and Artificial Intelligence, Vol. 1, No. 4, pp. 237–247, 2025, DOI: 10.61882/seai.2506-1028. (in Persian)
[15] M. H. Pranta, M. S. Rabbi, and M. M. Roshid, “A computational study on the aerodynamic performance of modified Savonius wind turbine,” Results in Engineering, Vol. 10, Art. no. 100237, 2021, DOI: 10.1016/j.rineng.2021.100237.
[16] S. Manavar, “CFD analysis of Savonius rotor with external deflectors of different shapes,” Renewable Energy, 2023.
[17] Y. Tian et al., “Optimization of deflector placement for vertical axis wind turbines,” Applied Energy, 2022.
[18] E. Fatahian, F. Ismail, M. H. H. Ishak, and W. S. Chang, “The role of wake splitter deflector on performance enhancement of Savonius wind turbine,” Physics of Fluids, Vol. 34, No. 9, Art. no. 095111, 2022, DOI: 10.1063/5.0111568. (in Persian)
[19] I. Marinić-Kragić, D. Vučina, and Z. Milas, “Robust optimization of Savonius-type wind turbine deflector blades considering wind direction sensitivity and production material decrease,” Renewable Energy, Vol. 192, pp. 150–163, 2022, DOI: 10.1016/j.renene.2022.04.118.
[20] K. R. Abdelaziz, M. A. A. Nawar, A. Ramadan, Y. A. Attai, and M. H. Mohamed, “Performance improvement of a Savonius turbine by using auxiliary blades,” Energy, Vol. 244, Art. no. 122575, 2022, DOI: 10.1016/j.energy.2021.122575.
[21] M. T. Bouzaher and B. Guerira, “Impact of flexible blades on the performance of Savonius wind turbine,” Arabian Journal for Science and Engineering, Vol. 47, pp. 15365–15377, 2022, DOI: 10.1007/s13369-022-06631-w.
[22] K. Mrigua, M. Zemamou, and M. Aggour, “Numerical investigation of a new modified Savonius wind turbines,” International Journal of Renewable Energy Development, Vol. 11, No. 4, pp. 1113–1123, 2022, DOI: 10.14710/ijred.2022.45799.
[23] F. Pallotta et al., “Recent trends in wind energy applications and the role of Savonius turbines,” Renewable Energy, 2020.
[24] M. M. H. Saikot, M. Rahman, M. A. Hosen, W. Ajwad, M. F. Jamil, and M. Q. Islam, “Savonius wind turbine performance comparison with one and two porous deflectors: A CFD study,” Flow, Turbulence and Combustion, Vol. 111, No. 4, pp. 1227–1251, 2023, DOI: 10.1007/s10494-023-00459-6.
[25] E. Fatahian et al., “Wake dynamics of Savonius turbines with modified external deflectors,” Renewable Energy, 2023. (in Persian)
[26] A. Abdelaziz et al., “Combined effect of deflector geometry and placement on Savonius rotor performance,” Renewable and Sustainable Energy Reviews, 2022.
[27] Z. Mansouri, M. Yadegari, and A. Bak Khoshnevis, “Numerical investigation of the effects of installing four trip wires with different diameters on the mean and fluctuation velocities and characteristics of the wake around the circular cylinder,” Journal of the Brazilian Society of Mechanical Sciences and Engineering, Vol. 45, No. 9, Art. no. 459, 2023, DOI: 10.1007/s40430-023-04409-1. (in Persian)
[28] M. Sadeghi, M. Yadegari, and A. B. Khoshnevis, “Numerical investigation of the flow characteristics around two sequential cylinders with circular and square cross-sections,” Journal of Marine Science and Technology, Vol. 29, pp. 315–332, 2024, DOI: 10.1007/s00773-024-00987-4. (in Persian)
[29] M. Yadegari and A. Bak Khoshnevis, “Numerical and experimental study of characteristics of the wake produced behind an elliptic cylinder with trip wires,” Iranian Journal of Science and Technology, Transactions of Mechanical Engineering, Vol. 45, No. 1, pp. 265–285, 2021, DOI: 10.1007/s40997-020-00373-6. (in Persian)
[30] R. E. Sheldahl, B. F. Blackwell, and L. V. Feltz, "Wind tunnel performance data for two- and three-bucket Savonius rotors," Journal of Energy, vol. 2, pp. 160–164, 1978, DOI: 10.2514/3.47966
 
 

  • Receive Date 25 September 2025
  • Revise Date 09 November 2025
  • Accept Date 03 December 2025
  • First Publish Date 03 December 2025
  • Publish Date 23 July 2026