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research-article

Performance Assessment of Transition Models for 3D flow over NACA4412 wings at Low Reynolds Numbers

[+] Author and Article Information
Ilyas Karasu

Adana Science and Technology University, Department of Aerospace Engineering, Gültepe Mahallesi, 01250, Sarıçam, Adana, Turkey
ikarasu@adanabtu.edu.tr

Mustafa Özden

Wind Engineering and Aerodynamic Research Laboratory, Department of Energy Systems Engineering, Erciyes University, 38039, Kayseri, Turkey
mustafaozden@gmail.com

M. Serdar Genç

Wind Engineering and Aerodynamic Research Laboratory, Department of Energy Systems Engineering, Erciyes University, 38039, Kayseri, Turkey
musgenc@erciyes.edu.tr

1Corresponding author.

ASME doi:10.1115/1.4040228 History: Received October 27, 2017; Revised May 03, 2018

Abstract

The performance of the transition models on 3D flow of wings with aspect ratios of 1 and 3 at low Reynolds number was assessed in this study. For experimental work; force measurements, surface oil and smoke-wire flow visualizations were performed over the wings with NACA4412 section at Reynolds numbers of 2.5x104, 5x104 and 7.5x104 and the angles of attack of 8°, 12° and 20°. Results showed that the aspect ratio had significant effects on the 3D flow structure over the wing. According to the experimental and numerical results, the flow over the wing having lower aspect ratios can be defined with wingtip vortices, axial flow and secondary flow including spiral vortex inside the separated flow. When the angle of attack and Reynolds number was increased, wing-tip vortices were enlarged and interacted with the axial flow. At higher aspect ratio, flow separation was dominant whereas wing-tip vortices suppressed the flow separation over the wing with lower aspect ratio. In the numerical results, while there were some inconsistencies in the prediction of lift coefficients; the predictions of drag coefficients for two transition models were noticeably better. The performance of the transition models judged from surface patterns was good, but the k-kL-? was preferable. Secondary flow including spiral vortices near the surface was predicted accurately by the k-kL-?. Consequently, in comparison with experiments, the predictions of the k-kL-? were better than those of the SST transition.

Copyright (c) 2018 by ASME
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