Modeling of the Separation Bubble on Cambered Airfoils Utilizing Modified Parameters in a Transition Model

Eren Anıl Sezer^1,2,3, Muhammer Ayvazoğlu^1,2, Muhammed Hatem^1,2, Sinem Keskin^1,2, Mustafa Özden^1,4, Mustafa Serdar Genç^1,3,*, Halil Hakan Açıkel¹
1 Wind Engineering and Aerodynamic Research Laboratory, Department of Energy Systems Engineering, Erciyes University, Kayseri, Türkiye
2 Graduate School of Natural and Applied Science, Erciyes University, Kayseri, Türkiye
3 MSG Teknoloji Ltd. Şti, Erciyes Teknopark Tekno-1 Binası, 61/20, Kayseri, Türkiye
4 Dominion Energy Innovation Center, Clemson University, North Charleston, SC, USA
* Corresponding Author: Mustafa Serdar Genç. Email: email
(This article belongs to the Special Issue: Modeling and Applications of Bubble and Droplet in Engineering and Sciences)

Computer Modeling in Engineering & Sciences https://doi.org/10.32604/cmes.2026.076446

Received 20 November 2025; Accepted 19 January 2026; Published online 13 February 2026

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Abstract

Separation bubbles forming on airfoils significantly influence aerodynamic behavior, particularly at low Reynolds numbers, making their accurate prediction a critical challenge in transition modelling. This study investigates numerical modeling of a separation bubble and the effects of airfoil thickness and camber variation on the formation of the bubble dynamics at low Reynolds numbers. The numerical results were compared with the experimental results obtained from surface pressure distribution measurements, oil flow visualisation, and surface shear measurements to analyse the detailed flow behavior. The combination of pressure and flow visualisation techniques provided complementary insights, enabling a detailed characterisation of bubble formation. The results reveal that both the thickness and camber of the airfoil significantly influence the location, length, and stability of the bubble. At low Reynolds number flows (Re = 0.5 × 10⁵), particularly for highly cambered profiles, closer to the leading edge, separation and long bubbles were observed. As the Reynolds number increased, the separation point shifted to the leading edge, and reattachment became more likely. In numerical studies, transition models can accurately model the bubble initiation point; however, they often fail to model the bubble reattachment points accurately. This is due to the inadequacy of models that use empirical expressions for turbulence modelling, particularly in low Reynolds number flows, in their viscous modelling. In this study, it was concluded that transition onset terms, which specifically affect bubble formation, should be modified for more accurate modeling.