Numerical simulation and experimental research on aerodynamic noises of the single wheel landing gear in an aircraft

Abstract

This paper established a computational model for the flow field of landing gear and extracted the velocity and vorticity distribution of flow field. A lot of shedding vortexes presented around the torque arm and pillar of landing gear and had the greatest impact on the flow field around the landing gear. Then, the aerodynamic noise of landing gear was measured in an anechoic chamber. The working noises of landing gear were more than background noises of landing gear. Their change trends were similar. Obvious peak frequencies presented at the front end of noise spectrum. In addition, peak frequencies increased with the increase of flow velocity. There were multiple peak frequencies on the curve of spectral characteristics. These frequencies were from pure sound in noises. Pure sound did not change with the change of flow velocity. The difference value of total sound pressure level of working noises and background noises was less than 10 dB. However, the difference value was bigger and bigger with the increase of flow velocity. When flow velocity was more than 50 m/s, background noises were over 10 dB lower than the total sound pressure level of working noises. Thus, it showed that the aerodynamic noise source of landing gear could be effectively recognized by experimental equipment. In addition, the total sound pressure level of aerodynamic noises of landing gear also increased with the increase of flow velocity and was directly proportional to the 6th power of flow velocity. The main noise source in experiments was dipole source. Finally, aerodynamic noises were obtained by AML model of landing gear, and compared with experimental results, showing consistent value and change trend. It showed that the computational model of noises was reliable. Based on the computational model of noises, this paper studied the contribution of pillar and torque arm of landing gear to radiation noises. Results showed that the pillar of landing gear was the main reason for radiation noises. In the future, pillar noises will be reduced through conducting structural design for the pillar of landing gear or applying sound package, further reducing radiation noises.