On the Aileron Buzz in the Transonic Flow
スポンサーリンク
概要
- 論文の詳細を見る
The fact that the flow pattern near the region of the shock-boundary layer interaction takes a certain finite delay time, which looks like depending mainly upon the thickness of the separated boundary layer induced by the shock wave, in adapting itself to the new steady flow pattern owing to the pressure impulses impinging on the region, is proved experimentally and it is pointed out that the delay time due to it is the main cause of the occurrence of the transonic aileron buzz and that the discussion of the phenomena on the basis of the go-and-return time for the pressure impulse with the sonic velocity between the shock and the aileron is inappropriate. It is also shown that the states of the aileron oscillation, which is neither convergent nor divergent, on a wing-aileron system under the same aerodynamic condition are always the same, that the angular velocities of aileron oscillation are inversely proportional to the square root of the aileron mass moment of inertia with the proportionality constant approximated by the square root of the aileron hinge moment coefficient in a steady-state flow, hence that the type of the oscillation is not a simple harmonic one, but a nonlinear oscillation with comparatively small terms associated with φ. Moreover, the greater the frequency of an aileron attached to the same wing is, the smaller the amplitude becomes and their product is always constant. The statement made in the literatures that the effect of a spring attached to a wing-aileron system has no connection with the aileron-buzz characteristics is not the case, but, naturally, the higher the stiffness of a spring is, the higher the frequency and the smaller the amplitude are. With a special wing-aileron system devised so as to suck out the thick boundary layer developed on the wing surfaces, the aileron buzz phenomena could be eliminated, so it was shown that the effect of the thick boundary layer on the time lag is very large. Based on these experimental facts, the equation governing the character of the aileron oscillation is proposed, which is a nonlinear differential equation with a hinge moment term proportional to the angular velocity of the aileron cubed, and its rationality is given by the analysis of the data obtained in Reference [9]. Lastly the methods to prevent the aileron buzz are described, which are performed by decreasing the delay time through the suction of the boundary layer flow or by increasing the frequency through the reduction of the weight of the aileron and the attachment of a spring.