Effects of adding strip flap on a plunging airfoil

Abstract

Purpose

The main aim of the present work is to examine the effects of trailing edge strip (TES) on the wake region of a plunging airfoil that oscillates prior and beyond the static stall angle of attack.

Design/methodology/approach

In this study, experimental investigations were carried out to explore the wake characteristics of a plunging Eppler 361airfoil equipped with TES flap. The experiments involved measurements of flapped and unflapped airfoil wake velocity for the range of initial AOA (0 and 12°). Surface pressure measurements as a supplementary data were also carried out. Data were taken at reduced frequencies of 0.03 and 0.073 and different distances downstream from trailing edge.

Findings

The results showed the hysteresis between the plunging wake in the upstroke and down-stroke motion. When the airfoil oscillated beyond the static stall angle of attack, huge variations on the wake profiles were found because of the interaction between LEV and Von Kármán vortices. More velocity defect in the wake region was realized by adding the TES but this effect was not the same for different phases of oscillation cycle. Also the power spectra of dominant frequencies and the extension of wake vortices were significantly increased by fitting the TES on the plunging airfoil.

Practical implications

The knowledge of the present study is necessary to enhance the performance of wind turbines, rotorcraft blades and maneuvering aircraft.

Originality/value

To date, no investigation has been conducted to determine the effects of a TES on the plunging airfoil aerodynamics.

Citation

Ajalli, F. and Mani, M. (2014), "Effects of adding strip flap on a plunging airfoil", Aircraft Engineering and Aerospace Technology, Vol. 86 No. 1, pp. 6-18. https://doi.org/10.1108/AEAT-08-2012-0129