An experimental study of acoustic disturbances effect on laminar separation bubble and transition over an aerofoil at low reynolds number


Hakan Açikel H., GENÇ M. S. , Tuǧrul Akpolat M., Karasu I.

6th AIAA Flow Control Conference 2012, New Orleans, LA, United States Of America, 25 - 28 June 2012 identifier

  • Publication Type: Conference Paper / Full Text
  • Volume:
  • City: New Orleans, LA
  • Country: United States Of America

Abstract

In this study, the effect of parallel acoustic excitation on laminar separation bubble over NACA2415 aerofoil and stall characteristics of the aerofoil were investigated at Re=50x103 and at various angles of attack. A sound source connected to a signal generator and an audio amplifier was placed in front of the wind tunnel to be parallel to the aerofoil. The amplitude of the sinusoidal sound wave was kept constant at 60 dB to determine the effects of varying frequencies from 70 Hz to 1100 Hz. In the experiments, an external three component load-cell system for force measurements, a scanivalve unit and a pressure transducer for pressure measurements and smoke-wire technique for flow visualization were used. The pressure measurement experiments showed that at the range of 200 Hz to 850 Hz the separated flow was reattached at the angle of attack of 15° and the laminar separation bubble was shortened at the angle of attack of 8° The shortened laminar separation bubble was seen clearly from some-wire flow visualization photos. Furthermore, the stall angle was delayed from αs=12° to αs=16° and CLmax was increased from 1.2 to 1.56 with acoustic excitation of 350 Hz. © 2012 by the American Institute of Aeronautics and Astronautics, Inc.