Noise Control Concepts for the Main Landing Gear of a Commercial Transport Aircraft

Project Description

Trends toward less complex high lift systems have meant that the noise associated with those components has reduced in recent years. The design of landing gear, however, has remained relatively constant and the associated noise has become significantly more important, particularly on approach. Further lowering of overall airplane noise is, therefore, heavily dependent on the reduction of landing gear noise. With the high costs of flight tests, the dependence on numerical simulations to evaluate noise reduction devices has increased. Langtry and Spalart [2] demonstrated that Reynolds-Averaged Navier-Stokes and DES could capture the landing gear cavity tone within 4 dB of experiments. They were also able to predict a significant tone reduction when a baffle is applied to the cavity. In this study, the range of resolved frequencies will be expanded due to the wide range of frequencies that the human ear is sensitive to and due to the range of frequencies associated with the landing gear. Computational aeroacoustics is a challenging field due to this wide range which requires a dense grid and small timestep for the high frequencies and a long time trace for the low frequencies. Due to these challenges it is difficult to perform computations over the range of frequencies of interest for complex geometries like the landing gear. Often the landing gear is overly simplified due to computational limitations. This simplification can alter the flow interactions with the different components of the gear and skew the noise prediction. For cases run on this allocation, the frequency range of interest will be resolved across the entire un-simplified gear. If these cases are successful in predicting the noise reduction between baseline and modified case, another Director’s Discretionary fund will be requested to test other more complex passive and active noise reduction concepts leading to a potential ALLC allocation for full-scale simulations of the airplane and main landing gear.