Aeroacoustic Study of a Generic Nose Landing Gear Focusing on Steering Mechanism

This study investigates the far-field aeroacoustic characteristics of a 30%-scale generic nose landing gear model, with particular emphasis on the influence of the steering mechanism. Phased-microphone array measurements were conducted in both the sideline and flyover directions for various configurations involving the strut, wheels, and two types of steering mechanisms. Results show that the bracket-type steering mechanism generates substantially higher noise levels than the integrated type, emerging as a major noise source above 3–4 kHz. Nevertheless, given its widespread use in commercial aircraft, the bracket steering mechanism is examined in greater detail. Its noise levels follow a rise-and-fall trend as the angle of the actuator cylinders in the steering mechanism increases from 0 to 90 deg relative to the streamwise direction, a behavior observed for both upstream and downstream placements of the mechanism relative to the strut. The acoustic signature of the bracket mechanism has a multipeak feature, with its overall shape following Strouhal-number-based scaling with the flow velocity to the sixth power, a feature attributable to vortex shedding from the bracket plates. From the noise localization maps, the major noise sources are identified to be on the bracket structure, while the actuators contribute negligible noise in comparison.