Wind-tunnel experiment of a friction drag reduction on an airfoil using uniform blowing

Eto, Kaoruko; Kondo, Yusuke; Fukagata, Koji; Tokugawa, Naoko

doi:10.1299/jsmekanto.2017.23.105

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“…Eto et al (2019) conducted a wind-tunnel experiment of UB at 0.14% free-stream velocity on an airfoil using air supply from an external compressor, i.e., active UB, and confirmed 20%-40% local friction drag reduction through a hot-wire measurement of velocity profiles and a quantitative assessment taking into account the pressure gradient. Although UB is generally known as an active control, Eto et al (2017) also attempted a passive blowing, which is driven by the pressure difference on a wing surface between suction and blowing region. They did not achieve an effective passive blowing due to the pressure loss mainly caused by the tubes and internal structure; however, they confirmed the feasibility of passive blowing and suggested structure of an airfoil to attain passive blowing with low pressure loss.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on friction drag reduction on an airfoil by passive blowing

Hirokawa¹,

Eto²,

Fukagata³

et al. 2020

JFST

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Friction drag reduction effect of a passive blowing on a Clark-Y airfoil is investigated. Uniform blowing, conducted in a wall-normal direction on a relatively wide surface, is generally known as an active control method for reduction of turbulent skin friction drag. In the present study, uniform blowing is passively driven by the pressure difference on a wing surface between suction and blowing regions. The suction and the blowing regions are respectively set around the leading edge and the rear part of the upper surface of the Clark-Y airfoil in order to ensure a sufficient pressure difference for passive blowing. The Reynolds number based on the chord length is 0.65×10 6 and 1.55×10 6. The angle of attack is set to 0 • and 6 •. The mean streamwise velocity profiles on the blowing region and the downstream, measured by a traversed hot-wire anemometry, are observed to shift away from the wall by passive blowing. This behavior qualitatively suggests reduction of local skin friction on the wing surface. A quantitative assessment of the friction drag is performed using the law of the wall accounting for pressure gradients (Nickels, 2004), coupled with a modified Stevenson's law (Vigdorovich, 2016) to account for the weak blowing. From this assessment, the local friction drag reduction effect of passive blowing is estimated to reach 4% − 23%.

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Section: Introductionmentioning

confidence: 99%