The research on active flow control method with vibration diaphragm on a NACA0012 airfoil at different stalled angles of attack

The flow control method with vibration diaphragm as a relatively new active flow control method has shown its great potential of improving flow field. A two-dimensional numerical computation for flow over an airfoil with vibration diaphragm is present at different stalled angles of attack and Re = 1.2 x 10(5). The vibration diaphragm is placed at the suction side of the airfoil surface near the leading edge and the length of the vibration diaphragm's projection along the chord direction is 0.1c. The effects of the dependant parameters dimensionless amplitude and frequency and the optimum parameters varying with different stalled angles of attack are investigated through enormous simulation data. Numerical results show that the lift coefficient and the lift-to-drag ratio increase firstly with the growth of the dimensionless frequency and then decrease. There exists the optimum dimensionless amplitude to make the control method behave best. The maximum increment of lift coefficient occurs at the low dimensionless frequency near 0.5, whereas for the lift-to-drag ratio, the maximum increment is attained the value of dimensionless frequency ranging from 1 to 1.5 at 16 degree angle of attack, the greatest improvement of the lift-to-drag ratio occurs when the value of dimensionless amplitude and frequency are 0.015 and 1.4, the maximum percent improvement is 91.31%. The oscillation coefficient is found to be a critical parameter to affect the lift-to-drag ratio of the airfoil and there exits an optimum oscillation coefficient to obtain greatest improvement of lift-to-drag ratio. The optimum parameters of the control methods to achieve the highest lift-to-drag ratio vary with different stalled angles of attack, with the growth of the angles of attack, the optimum dimensionless amplitude increases, the optimum dimensionless frequency decreases firstly and then keep the certain value 1.1 and the oscillation coefficient fluctuates weakly in the range of 1.15-1.3. (C) 2017 Elsevier Masson SAS. All rights reserved.