Effect of Semi-elliptical Outer Blade-surface on the Savonius Hydrokinetic Turbine Performance: A Numerical Investigation

Document Type : Regular Article


School of Mechanical Engineering, Vellore Institute of Technology, Vellore – 632014, India



The Savonius hydrokinetic turbine (SHT) is widely used for generating electricity from running water. However, most optimization work has been carried out on conventional blades with similar concave and convex profiles. This study aims to enhance SHT performance by modifying the rotor blades' outer surface radius (0.079, 0.087 and 0.095 m) to create a semi-elliptical shape, thus reducing opposing forces. The tip speed ratio (TSR) varies from 0.5 to 1.3 with an interval of 0.1. A constant channel velocity of 0.8 m/s at Re = 2.25 × 105 is considered for the analysis. The flow field has been numerically investigated using the SST k - ω model. This study comprises the angular variation in the coefficients of power (Cp) and torque (Cm), performance curves of the rotor, and pressure distribution on the blade surface at different angular positions. It is observed that the rotor with a radius of 0.095 m has a maximum Cp value of 0.142, which is 7.57% and 18.33% higher than the Cp values of rotors with radii of 0.079 m and 0.087 m, respectively. The maximum power output of the rotor with a radius of 0.095 m is 2.32 W, whereas the power outputs of the rotors with radii of 0.087 m and 0.079 m are 2.16 W and 1.96 W, respectively. An increase in the instantaneous values of Cm between rotation angles 0 to 115 is observed, during which the returning blades mainly interact with the incoming stream. The pressure decreases as the radius of the semi-elliptical outer surface increases at rotor positions ranging from 0 to 225, but it increases at rotor positions ranging from 270 to 315.


Main Subjects

Abdelghafar, I., Kerikous, E., Hoerner, S., & Thévenin, D. (2023). Evolutionary optimization of a Savonius rotor with sandeel-inspired blades. Ocean Engineering, 279. https://doi.org/10.1016/j.oceaneng.2023.114504
Alizadeh, H., Jahangir, M. H., & Ghasempour, R. (2020). CFD-based improvement of Savonius type hydrokinetic turbine using optimized barrier at the low-speed flows. Ocean Engineering, 202, 107178. https://doi.org/10.1016/j.oceaneng.2020.107178
Al-Obaidi, A. (2023a). Effect of different guide vane configurations on flow field investigation and performances of an axial pump based on CFD analysis and vibration investigation. Experimental Techniques. https://doi.org/10.1007/s40799-023-00641-5
Al-Obaidi, A. R. & Alhamid, J. (2023). Investigation of the main flow characteristics mechanism and flow dynamics within an axial flow pump based on different transient load conditions. Iranian Journal of Science and Technology Transactions of Mechanical Engineering, 47,  1397–1415.https://doi.org/10.1007/s40997-022-00586-x
Al-Obaidi, A. (2018). Experimental and numerical investigations on the cavitation phenomenon in a centrifugal pump. [Doctoral thesis, University of Huddersfield]. http://eprints.hud.ac.uk/id/eprint/34513/
Al-Obaidi, A. R. (2019). Investigation of effect of pump rotational speed on performance and detection of cavitation within a centrifugal pump using vibration analysis. Heliyon, 5. https://doi.org/10.1016/j.heliyon.2019.e01910
Al-Obaidi, A. R. (2023b). Experimental diagnostic of cavitation flow in the centrifugal pump under various impeller speeds based on acoustic analysis method. Archives of Acoustics, 48(2), 159–170. https://doi.org/10.24425/aoa.2023.145234
Al-Obaidi, A. R., Khalaf, H. A. & Alhamid, J. (2023a). Investigation of the influence of varying operation configurations on flow behaviors characteristics and hydraulic axial-flow pump performance. ICONSEIR. http://dx.doi.org/10.4108/eai.24-11-2022.2332719 
Al-Obaidi, A. R., Khalaf, H. A. & Alhamid, J. (2023b). Investigation on the characteristics of internal flow within three-dimensional axial pump based on different flow conditions. ICONSEIR. http://dx.doi.org/10.4108/eai.24-11-2022.2332720
Al-Obaidi, A., & Qubian, A. (2022). Effect of outlet impeller diameter on performance prediction of centrifugal pump under single-phase and cavitation flow conditions. International Journal of Nonlinear Sciences and Numerical Simulation, 23(7-8), 1203-1229. https://doi.org/10.1515/ijnsns-2020-0119
Anthony, A. Z. & Roy, S. (2020). Performance analysis of a modified Savonius hydrokinetic turbine blade for rural application. IOP Conference Series: Materials Science and Engineering, 943. https://doi.org/10.1088/1757-899X/943/1/012034
Salleh, M. B., Kamaruddin, N. M., & Mohamed-Kassim, Z. (2019). Savonius hydrokinetic turbines for a sustainable river-based energy extraction: A review of the technology and potential applications in Malaysia. Sustainable Energy Technologies and Assessments, 36, 100554. https://doi.org/10.1016/j.seta.2019.100554
Basumatary, M., & Biswas, A. (2016). Numerical simulation of two-bladed Savonius water turbine with deflector. International Journal of Renewable Energy Technology, 7(4), 383. https://doi.org/10.1504/IJRET.2016.080115
Basumatary, M., Biswas, A., & Misra, R. D. (2018). CFD analysis of an innovative combined lift and drag (CLD) based modified Savonius water turbine. Energy Conversion and Management, 174, 72–87. https://doi.org/10.1016/j.enconman.2018.08.025
Boccaletti, C., Fabbri, G., Marco, J., & Santini, E. (2008). An overview on renewable energy tech- nologies for developing countries: The case of Guinea Bissau. Renewable Energy and Power Quality Journal, 1(6), 343–348. https://doi.org/10.24084/repqj06.295
Chen, Y., Chen, Y., Zhou, J., Guo, P., & Li, J. (2023). Optimization and performance study of bidirectional Savonius tidal turbine cluster with deflectors. Energy Conversion and Management, 283. https://doi.org/10.1016/j.enconman.2023.116947 
Golecha, K., Eldho, T. I., & Prabhu, S. V. (2011). Influence of the deflector plate on the performance of modified Savonius water turbine. Applied Energy, 88, 3207–17. https://doi.org/10.1016/j.apenergy.2011.03.025.
Hayashi, T., Li, Y., & Hara, Y. (2005). Wind tunnel tests on a different phase three-stage Savonius rotor. JSME International Journal, Series B: Fluids and Thermal Engineering, 48(1), 9–16. https://doi.org/10.1299/jsmeb.48.9
Jeong, J., & Hussain, F. (1995). On the identification of a vortex. Journal of Fluid Mechanics, 285, 69–94. https://doi.org/10.1017/S0022112095000462
Kacprzak, K., Liskiewicz, G., & Sobczak, K. (2013). Numerical investigation of conventional and modified Savonius wind turbines. Renewable Energy, 60, 578–585. http://dx.doi.org/10.1016/j.renene.2013.06.009
Kailash, G., Eldho, T. I., & Prabhu, S. V. (2012). Performance study of modified savonius water tur- bine with two deflector plates. International Journal of Rotating Machinery, 2012. https://doi.org/10.1155/2012/679247
Kamal, M. M., & Saini, R. P. (2022). A review on modifications and performance assessment techniques in cross-flow hydrokinetic system. Sustainable Energy Technologies and Assessments, 51, 101933. https://doi.org/10.1016/j.seta.2021.101933
Kamoji, M. A., Kedare, S. B., & Prabhu, S. V. (2008). Experimental investigations on single stage, two stage and three stage conventional Savonius rotor. International Journal of Energy Research, 32, 877–895. https://doi.org/10.1002/er.1399
Khan, M. N. I., Tariq Iqbal, M., Hinchey, M., & Masek, V. (2009). Performance of savonius rotor as a water current turbine. Journal of Ocean Technology, 4(2), 71–83. http://research.library.mun.ca/id/eprint/235
Kumar, A., & Saini, R. P. (2017). Performance analysis of a single stage modified Savonius hydrokinetic turbine having twisted blades. Renewable Energy, 113, 461–478. https://doi.org/10.1016/j.renene.2017.06.020
Mahmoud, N. H., El-Haroun, A. A., Wahba, E., & Nasef, M. H. (2012). An experimental study on improvement of Savonius rotor performance. Alexandria Engineering Journal, 51(1), 19–25. http://dx.doi.org/10.1016/j.aej.2012.07.003
Menter, F. R. (1994). Two-equation eddy-viscosity turbulence models for engineering applications. AIAA Journal, 32(8), 1598–1605. https://doi.org/10.2514/3.12149
Mohamed, M. H., Janiga, G., Pap, E., & Thévenin, D. (2010). Optimal performance of a modified three-blade savonius turbine using frontal guiding plates. Proceedings of the ASME Turbo Expo. https://doi.org/10.1115/GT2010-22538
Nag, A. K. & Sarkar, S. (2020). Experimental and numerical study on the performance and flow pattern of different Savonius hydrokinetic turbines with varying duct angle. Journal of Ocean Engineering and Marine Energy,  6, 31–53. https://doi.org/10.1007/s40722-019-00155-6
OpenFOAM (2017). The Open Source CFD Toolbox User Guide.https://www.openfoam.com/documentation/user-guide.
Patankar, S. (1980). Numerical heat transfer and fluid flow. CRC press.
Patel, V., Bhat, G., Eldho, T. I., & Prabhu, S. V. (2016). Influence of overlap ratio and aspect ratio on the performance of Savonius hydrokinetic turbine. International Journal of Energy Research, 41(6), 829– 844. https://doi.org/10.1002/er.3670
Roy, S., & Ducoin, A. (2016). Unsteady analysis on the instantaneous forces and moment arms acting on a novel Savonius-style wind turbine. Energy Conversion and Management, 121, 281–296. http://dx.doi.org/10.1016/j.enconman.2016.05.044
Salleh, M. B., Kamaruddin, N. M., & Mohamed Kassim, Z. (2020). The effects of a deflector on the self-starting speed and power performance of 2- bladed and 3-bladed Savonius rotors for hydrokinetic application. Energy for Sustainable Development, 61(1), 168–180. https://doi.org/10.1016/j.esd.2021.02.005
Sarma, N. K., Biswas, A., & Misra, R. D. (2014). Experimental and computational evaluation of Savonius hydrokinetic turbine for low velocity condition with comparison to Savonius wind turbine at the same input power. Energy Conversion and Management, 83, 88–98. https://doi.org/10.1016/j.enconman.2014.03.070
Setiawan, P. A., Yuwono, T., & Widodo, W. A. (2019a). Effect of a circular cylinder in front of advancing blade on the savonius water turbine by using transient simulation. International Journal of Mechanical and Mechatronics Engineering, 19(1), 151–159. https://api.semanticscholar.org/CorpusID:221793287
Setiawan, P. A., Yuwono, T., Widodo, W. A., Julianto, E., & Santoso, M. (2019b). Numerical study of a circular cylinder effect on the vertical axis savonius water turbine performance at the side of the advancing blade with horizontal distance variations. International Journal of Renewable Energy Research, 9(2), 978–985. https://doi.org/10.20508/ijrer.v9i2.8890.g7662
Talukdar, P. K., Sardar, A., Kulkarni, V., & Saha, U. K. (2018). Parametric analysis of model Savonius hydrokinetic turbines through experimental and computational investigations. Energy Conversion and Management, 158, 36–49. https://doi.org/10.1016/j.enconman.2017.12.011
Tartuferi, M., D’Alessandro, V., Montelpare, S., & Ricci, R. (2015). Enhancement of savonius wind rotor aerodynamic performance: A computational study of new blade shapes and curtain systems. Energy, 79(C), 371–384. http://dx.doi.org/10.1016/j.energy.2014.11.023
Tian, W., Mao, Z., Zhang, B., & Li, Y. (2017). Shape optimization of a Savonius wind rotor with different convex and concave sides. Renewable Energy, 117, 287–299. https://doi.org/10.1016/j.renene.2017.10.067
Tian, W., Song, B., Van Zwieten, J. H., & Pyakurel, P. (2015). Computational fluid dynamics prediction of a modified savonius wind turbine with novel blade shapes. Energies, 8(8), 7915–7929. https://doi.org/10.3390/en8087915
Wahyudi, B., Soeparman, S., Wahyudi, S., & Denny, W. (2013). A Simulation study of flow and pres- sure distribution patterns in and around of tan- dem blade rotor of Savonius (TBS) hydrokinetic turbine model. Journal of Clean Energy Technologies, 286–291. https://doi.org/10.7763/jocet.2013.v1.65
Wong, K. H., Chong, W. T., Sukiman, N. L., Poh, S. C., Shiah, Y. C., & Wang, C. T. (2017). Performance enhancements on vertical axis wind turbines using flow augmentation systems: A review. Renewable and Sustainable Energy Reviews, 73, 904–921. https://doi.org/10.1016/j.rser.2017.01.160
Yao, J., Li, F., Chen, J., Yuan, Z., & Mai, W. (2019). Parameter analysis of savonius hydraulic turbine considering the effect of reducing flow velocity. Energies, 13. https://doi.org/10.3390/en13010024
Zhao, Z., Zheng, Y., Xu, X., Liu, W., and Hu, G. (2009). Research on the improvement of the performance of savonius rotor based on numerical study. 1st International Conference on Sustainable Power Generation and Supply, SUPERGEN 09, 1–6. https://doi.org/10.1109/SUPERGEN.2009.5348197