Abstract
The landing gear is widely concerned as the main noise source of airframe noise. The flow characteristics and aerodynamic noise characteristics of the landing gear were numerically simulated based on Large Eddy Simulation and Linearized Euler Equation, and the feasibility of the simulation model was verified by experiments. Then the wind speed effect on the flow and acoustic characteristics of the minor cavity structures in a two-wheel landing gear were analyzed. The results show that the interaction of vortices increases with the increase of velocity at the brake disc, resulting in a slight increase in the amplitude of pressure fluctuation at 55 m·s−1~75 m·s−1. With the increase of speed, the obstruction at the lower hole of torque link decreases, and many vortical structures flow out of the lower hole and are dissipated, so that the pressure fluctuation amplitude of 75 m·s−1 almost does not increase relative to 55 m·s−1. The contribution of each part in the landing gear to the overall noise is as follows: shock strut > tire > torque link > brake disc. At the speed of 34 m·s−1~55 m·s−1, the contribution of each component to the total noise increases with the increase of speed, and the small components such as torque link and brake disc contribute more to the total noise. At the speed of 55 m·s−1~75 m·s−1, the increase of overall noise mainly comes from the main components such as shock strut and tire, and the brake disc and torque link contribute very little to the overall noise. It provides a reference for the further noise reduction optimization design of the landing gear.
Highlights
With the progress of aircraft engine noise reduction technology, airframe noise has been identified as a new challenge to the aeronautical industry [1]
The color indicates the change of Mach number. It can be seen from the figure that complex vortical structure is formed at the tail of the landing gear, thereby forming a complex flow field change, which generates aerodynamic noise
The amplitude of the sound pressure level of the torque link and brake disc increases significantly, which has a great impact on the total noise. (III) At the speed of 55 m·s−1 to 75 m·s−1, the amplitude of sound pressure level of torque link and brake disc increases slightly, and the contribution to the total noise decreases obviously
Summary
With the progress of aircraft engine noise reduction technology, airframe noise has been identified as a new challenge to the aeronautical industry [1]. A European Co-financed project called TIMPAN (“Technology to IMprove Airframe Noise”) was launched [2] It mainly studied some more advanced low-noise designs for aircraft landing gear and the high lift wing. There are relatively few numerical studies of the wind speed effect on the flow and acoustic characteristics of the minor cavity structures in two-wheel landing gears. The landing gear test was carried out based on FL-17 wind tunnel (Section 2), and the landing gear numerical model was established based on LES/LEE method, which is verified by experiments (Section 3). The effects of wind speed on the flow and acoustic characteristics of the minor cavity structures in two-wheel landing gears (brake disc and torque link) are further analyzed (Section 4). The landing gear was installed on a test platform measuring 13.5 m (length in the direction of incoming flow) × 8.6 m (width) × 6 m (height)
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