AUT Journal of Mechanical Engineering

AUT Journal of Mechanical Engineering

Experimental Investigation of Enhanced Shroud Flange Designs for Improved Urban Wind Turbine Performance in Low-Wind Conditions

Document Type : Research Article

Authors
Ali Niknahad 1
Abdolamir Bak-khoshnevis 2
Morteza Abdolzadeh 3
1 Department of Mechanical Engineering, Hakim Sabzevari University, Sabzevar, Iran.
2 Department of Mechanical Engineering, Hakim Sabzevari University, Sabzevar, Iran
3 Department of Mechanical Engineering, Kerman Graduate University of Technology, Kerman, Iran.
10.22060/ajme.2026.23926.6167
Abstract
The growing demand for sustainable energy highlights the need for efficient small-scale wind turbines, especially in urban areas with low wind speeds and limited space. This study experimentally examines aerodynamic augmentation effects on turbine performance using shrouds and tailored flanges. Four turbine configurations—a bare turbine, a turbine with a simple shroud, a shroud with a vertical flange, and a shroud with an improved curved flange—were 3D printed and tested in a controlled wind tunnel under realistic low- to moderate-speed urban wind conditions. Airflow velocity at the shroud throat and corresponding power output were measured across various wind speeds. Results show that both flange curvature and height significantly affect aerodynamic performance. The curved-flange design consistently increased throat velocity and turbine output, achieving up to a 32.3-fold power gain over the bare turbine at 5 m/s. At higher wind speeds, differences among augmented configurations decreased, yet the improved curved flange still delivered approximately 4.3 times the output of the bare turbine at 16.35 m/s. These findings emphasize the importance of outlet geometry in lowering startup thresholds, sustaining airflow acceleration, and maximizing energy capture. Overall, this study provides robust experimental evidence that shrouds with improved curved flanges significantly enhance small-scale urban wind turbine efficiency, offering a practical solution for low-wind energy harvesting and guiding future designs for improved performance across diverse wind regimes.
Keywords
Shroud
Flange
Wind Turbine
Computational Fluid Dynamics
Wind Tunnel
Experimental Approach
Subjects
[1] A.C. Aranake, V.K. Lakshminarayan, K. Duraisamy, Computational analysis of shrouded wind turbine configurations using a 3-dimensional RANS solver, Renewable Energy, 75 (2015) 818–832..
[2] A. Aranake, K. Duraisamy, Aerodynamic optimization of shrouded wind turbines, Wind Energy, 20(5) (2017) 877–889.
[3] A. Dilimulati, T. Stathopoulos, M. Paraschivoiu, Wind turbine designs for urban applications: A case study of shrouded diffuser casing for turbines, Journal of Wind Engineering and Industrial Aerodynamics, 175 (2018) 179–192.
[4] M. Shahsavarifard, E.L. Bibeau, Performance characteristics of shrouded horizontal axis hydrokinetic turbines in yawed conditions, Ocean Engineering, 197 (2020) 106916.
[5] N.K. Siavash, G. Najafi, T.T. Hashjin, B. Ghobadian, E. Mahmoodi, An innovative variable shroud for micro wind turbines, Renewable Energy, 145 (2020) 1061–1072.
[6]S.D. Karmakar, H. Chattopadhyay, A review of augmentation methods to enhance the performance of vertical axis wind turbine, Sustainable Energy Technologies and Assessments, 53 (2022) 102469.
[7]A. Ilhan, B. Sahin, M. Bilgili, A review: diffuser augmented wind turbine technologies, International Journal of Green Energy, 19(1) (2022) 1–27.
[8] R. Bontempo, E. Di Marzo, M. Manna, Diffuser augmented wind turbines: A critical analysis of the design practice based on the ducting of an existing open rotor, Journal of Wind Engineering and Industrial Aerodynamics, 238 (2023) 105428.
[9] W. Han, P. Yan, W. Han, Y. He, Design of wind turbines with shroud and lobed ejectors for efficient utilization of low-grade wind energy, Energy, 89 (2015) 687–701.
[10] B. Kosasih, A. Tondelli, Experimental study of shrouded micro-wind turbine, Procedia Engineering, 49 (2012) 92–98.          
[11] N.A. Pambudi, R. Febriyanto, K.M. Wibowo, N.D. Setyawan, N.S. Wardani, L.H. Saw, B. Rudiyanto, The performance of shrouded wind turbine at low wind speed condition, Energy Procedia, 158 (2019) 260–265.
[12] B.A. Alquraishi, N.Z. Asmuin, S. Mohd, W.A. Abd Al-Wahid, A.N. Mohammed, Review on diffuser augmented wind turbine (dawt), International Journal of Integrated Engineering, 11(1) (2019).
[13] S.N. Akour, M.A.A. Mhaisen, Parametric design analysis of elliptical shroud profile, AIMS Energy, 9(6) (2021) 1147–1169.
[14] S.N. Leloudas, G.N. Lygidakis, A.I. Eskantar, I.K. Nikolos, A robust methodology for the design optimization of diffuser augmented wind turbine shrouds, Renewable Energy, 150 (2020) 722–742.
[15]Y. Ohya, T. Karasudani, A. Sakurai, K.-i. Abe, M. Inoue, Development of a shrouded wind turbine with a flanged diffuser, Journal of wind engineering and industrial aerodynamics, 96(5) (2008) 524–539.
[16] A. Niknahad, A. Khoshnevis, Numerical Investigation Of The Best Wind Turbine Shroud Flange Curvature For Maximum Wind Power Extraction, AUT Journal of Mechanical Engineering, 7(2) (2023) 185–198.
[17]M. Lipian, I. Dobrev, M. Karczewski, F. Massouh, K. Jozwik, Small wind turbine augmentation: Experimental investigations of shrouded-and twin-rotor wind turbine systems, Energy, 186 (2019) 115855.
[18]M. Lipian, I. Dobrev, F. Massouh, K. Jozwik, Small wind turbine augmentation: Numerical investigations of shrouded-and twin-rotor wind turbines, Energy, 201 (2020) 117588.
[19] M. Amin, H.H.M. ZoheirSaboohi, K.G. Osgouie, Investigation of the factors affecting the performance of Savonius wind turbine, Journal of Renewable Energy and New Energy, 10(2) (2023).
[20] S.E. Hosseini, Z. Saboohi, Ducted wind turbines: A review and assessment of different design models, Wind Engineering,  (2024) 0309524X241282090.
[21] N. Maftouni, M. Taghaddosi, A CFD study of a flanged shrouded wind turbine: Effects of different flange surface types on output power, Scientia Iranica, 29 (1) (2022) 101–108.
[22] J.F. Hu, W.X. Wang, Upgrading a shrouded wind turbine with a self-adaptive flanged diffuser, Energies, 8 (6) (2015) 5319–5337.
[23] L. Gish, A. Carandang, G. Hawbaker, Experimental evaluation of a shrouded horizontal axis hydrokinetic turbine with pre-swirl stators, Ocean Engineering, 204 (2020) 107252.
[24] M.L. Hossain, S.N. Shams, S.M. Ullah, Comparative study of machine learning algorithms for wind speed prediction in Dhaka, Bangladesh, Sustainable Energy Research, 11(1) (2024) 23.
[25]Q. Zhang, D. Zhou, D. Xu, A. Rogora, Association between wind environment and spatial characteristics of high-rise residential buildings in cold regions through Field Measurements in Xi’an, Buildings, 13(8) (2023) 2007.
 [26] K. Piasecki, E. Żmudzka, Severe storms as an example of a natural hazard in the urban area-case studies of the area of Warsaw, Poland, Miscellanea Geographica. Regional Studies on Development, 26(1) (2022) 63–74. 
 [27] V. Ok, M. Aygün, The variations of wind speeds with building density in urban areas, Architectural Science Review, 38(2) (1995) 87–95.
AUT Journal of Mechanical Engineering
Volume 10, Issue 3
2026
Pages 297-318