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ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 2016, Vol. 37 ›› Issue (4): 1139-1147.doi: 10.7527/S1000-6893.2015.0208

• Fluid Mechanics and Flight Mechanics • Previous Articles     Next Articles

Aerodynamic characteristics and flow control on a rectangular wing at low Reynolds number

ZUO Wei1, GU Yunsong1, WANG Qite1, ZHENG Yueyang1, LIU Yuan2   

  1. 1. College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;
    2. Engineering Training Center, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
  • Received:2015-05-18 Revised:2015-07-18 Online:2016-04-15 Published:2015-07-30
  • Supported by:

    A Project Funded by the Priority Academic Progran Development of Jiangsu Higher Education Institutions

Abstract:

It is found that the flight environment in thin atmosphere and at low Reynolds number leads to the drop of high-altitude long-endurance unmanned aerial vehicles (HALE UAV) aerodynamic performance, and as a result, how to improve it with flow control has drawn greater attention of researchers. An experimental investigation on the aerodynamic characteristics and flow control of a NACA 633-421 rectangular wing at low Reynolds number is conducted in a low-speed wind tunnel with force measurement,pressure measurement and boundary layer test. It is shown from force measurement result that a sharp deterioration of aerodynamic characteristics of NACA 633-421 wing occurs with the Reynolds number decreasing(Re<1.4×105), which includes severe losses of the maximum lift coefficient with respect to higher Reynolds numbers and the sharp decrease of stall angle. Pressure distribution on upper surface reveals that the emergence and development process of a laminar separation bubble (LSB), which moves forward to the wing leading edge, becomes shorter in length with increasing angles of attack and bursts at the stall angle, finally cause the sharp deterioration of aerodynamic characteristics. The micro synthetic jet (Micro-SJ) is used to control the flow structure of laminar separation bubbles, as a result of which the maximum lift coefficient increases from 0.59 to 1.10, the stall is delayed by 11° and the maximum lift-drag ratio is improved by 13.6% meanwhile. The active flow control of Micro-SJ possesses frequency selectivity, in which case the Micro-SJ at the frequencies between 200 Hz to 400 Hz have the best flow control effects to promote the transition of the separated shear layer and to shorten the length of laminar separation bubbles.

Key words: low Reynolds number, laminar separation bubble, micro synthetic jet, flow control, control frequency, separated shear layer

CLC Number: