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Wei L.-K.,Beihang University | Wei L.-K.,Key Laboratory of Fluid Mechanics | Ma B.-F.,Beihang University | Ma B.-F.,Key Laboratory of Fluid Mechanics
Journal of Aircraft | Year: 2014

The wing rock induced by a hemisphere-cylinder forebody was investigated experimentally using an isolated delta wing and wing body. For the delta wing with sweep angle of 30 deg, no apparent limit-cycle wing rock occurs at angles of attack of 0-90 deg. The mean roll angles exhibit nonzero values at angles of attack of less than 15 deg and become zero at angles of attack of more than 15 deg. For the wing body with a hemisphere-cylinder forebody, apparent wing rock exists at angles of attack of 0-90 deg; the wing rock is induced by the forebody. The phase diagrams showed that the wing rock motion is a typical limit-cycle oscillation at lower and moderate angles of attack. With increasing angles of attack, however, stochastic components in wing rock motion are increased gradually, and the motion types start to deviate from a limit-cycle oscillation. The phase-locked particle-image-velocimetry measurements for the wing body revealed that the vortex pair over the forebody exhibits apparent dynamic hysteresis in position and strength during wing rock, and the dynamic hysteresis of forebody vortices further influence flowfields over the wing, resulting in asymmetric distributions of wing flow, which provides the driving moments sustaining the wing rock. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source


Zhang P.,Shanghai JiaoTong University | Zhang P.,CAS Institute of Mechanics | Yan B.,CAS Institute of Mechanics | Yan B.,Key Laboratory of Fluid Mechanics | And 2 more authors.
Science China Technological Sciences | Year: 2012

A novel circulation control technique is proposed to overcome the shortcomings of blowing jet circulation control, which uses the synthetic jet as the actuator and avoids the limitation about air supply requirement. The effectiveness of synthetic jet circulation control to enhance lift of NCCR1510-7067N airfoil is confirmed by solving the 2-D unsteady Reynolds-averaged Navier-Stokes equations. The aerodynamic characteristics and the flow structure (especially close to the trailing edge) of NCCR1510-7067N airfoil at zero angle of attack are also presented to discuss the mechanism of lift enhancement of the airfoil with synthetic jet circulation control. The results indicate that the synthetic jet can effectively delay the separation point on the airfoil trailing edge and increase the circulation and lift of the airfoil by Coanda effect. The numerical simulation results demonstrate that the lift augmentation efficiency with synthetic jet circulation control reaches ΔC L/C μ =114 in the present study, which is much higher than the value 12.1 in the case with steady blowing jet circulation control. © Science China Press and Springer-Verlag Berlin Heidelberg 2012. Source


Zhang P.,Beihang University | Zhang P.,Key Laboratory of Fluid Mechanics | Dai C.,Beihang University | Liu A.,Beihang University | And 2 more authors.
Science China Technological Sciences | Year: 2011

The flow induced by plasma synthetic jet actuator was simulated through solving the Reynolds-averaged Navier-Stokes equations augmented by body force phenomenological plasma model. The effect of actuation frequency on the plasma synthetic jet was examined by case study. The numerical results present that with the actuation frequency increasing, the stream-wise distance of the adjacent vortex pairs induced by the actuator decreases monotonically, which is the same as the situation of the velocity fluctuations field caused by the vortex pairs. When the actuation frequency is 60 Hz, the vortex pairs formed during the adjacent actuation periods merge together quickly, and the flow structure in the downstream region is more close to that of the steady case. The actuation frequency has no visible influence on the time-averaged flow field of plasma synthetic jet. However, when the actuation frequency is relatively low (f<40 Hz), the momentum flux close to the actuator increases with the actuation frequency increasing, which is contrary to the situation in the far field from the wall. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg. Source


Feng Z.P.,Beihang University | Feng Z.P.,Key Laboratory of Fluid Mechanics | Bing L.A.,Beihang University | Jun W.J.,Beihang University | Jun W.J.,Key Laboratory of Fluid Mechanics
Science China Technological Sciences | Year: 2010

The flow field in the flat plate boundary layer induced by the pulsed plasma actuator was simulated by solving the Navier-Stokes equations with a phenomenological DBD plasma model. The effects of actuation strength, wave form and frequency on the flow structures induced by the unsteady pulsed plasma actuator were investigated. The results indicated that a series of vortex pairs were formed in the boundary layer, and decayed in downstream convection following the exponential law. The strength of vortex pair was dominated by the effective plasma actuation strength, and the vortex streamwise spacing depended on the actuation frequency. If the duty cycle is not so large that interaction of adjacent vortex pairs can be negligible, then the actuation wave form has little influence on the vortex pair induced by the unsteady plasma actuator. © Science China Press and Springer-Verlag Berlin Heidelberg 2010. Source

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