Study On The Characteristics And Control Methods Of Slat Noise

Aeroacoustic noise from the civil aircraft is not only related to its airworthiness, but also related to its comfort requirements. Noise generated by slat is a major contributor to the overall airframe noise. Analysis and control of slat noise has the significance. Prediction, control, and mitigation of slat noise require a thorough understanding of the flow physics and underlying noise mechanisms. In this paper, the flow physics and underlying noise mechanisms of slat cove in two airfoil systems are summarized in detail. Based on this, we introduce two methods of noise control. One is the suction control, and its effectiveness is verified by simulative results; the other is the vibration excitation control with piezoelectric materials, and its control effect is analyzed by experiment.In detail, the research work of this thesis mainly consists of the following three parts:First, noise characteristics, prediction methods and reduction of slat noise are reviewed based on current research status at home and abroad. Then, aeroacoustics is analyzed from the basic equations of fluid dynamic and acoustic.Second, numerical simulations are performed to investigate the aerodynamic and aeroacoustic characteristic of a three-element airfoil system. The results show that the slat reattachment region is a strong source of noise. Based on this, the dissertation proposes a method of noise control with suction near the reattachment region, and deeply studies the impact on the flow field and far field noise. The introduction of the suction control will not affect the high-lift performance of this configuration. The suction control reduces the strength of vortex-body interaction significantly demonstrating its high ability in slat noise suppression. The results, achieved by numerical method, show both the broadband component and multiple tonal peaks of slat noise are reduced.Third, experiments are performed to investigate the flow field and noise characteristics of a two-element airfoil system. The multiple tonal peaks of slat noise are identified by sound intensity technology. A method of noise control, active vibration excitation, is proposed and validated. The results, achieved by experiment, show the introduction of the vibration excitation can break the feedback mechanism of slat cove. And this control method has influence on multiple tonal peaks of slat noise.