Understanding the fluctuating flow around two-wheel landing gear systems and innovative solutions for noise mitigation

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Since the dawn of commercial aviation, noise pollution has been a negative by-product of aircraft. Several surveys have shown direct associations between extended exposure to aircraft noise and various health problems. As a result of strong public response to this issue, noise policies became periodically more and more stringent over the years, and owing to this shift, today, the noisiest aircraft from past (those designed before 1978) can no longer operate on commercial routes. The phasing out of aircraft as a consequence of the increasingly stringent noise policies implies that the retained value of an aircraft may dramatically reduce at a certain point in its life if it does not have much margin for use before being phased out of operation. In addition, based on their noise emission, aircraft are often charged fees per landing, which over a typical year of operation with numerous flights can be a significant cost to airline operators. For these reasons, airlines are more inclined towards purchasing quieter aircraft. This puts all the large aircraft manufacturers into a competition to design the quietest aircraft. So far, the success of aircraft manufacturers in noise reduction has been mostly through the improvements in engine technology and the state achieved today is such that, during approach to landing, the noise generated by landing gears is almost equal to that generated by the engines. Landing gear noise mainly results from the unsteady flow structures that are generated around landing gear and their complex interactions with the aircraft components. At this point, the basic mechanisms of landing gear noise generation are still not well understood and it is therefore difficult to develop efficient strategies to mitigate against them. The proposed research program will identify the possible causes and sources of noise generation for landing gears by developing a comprehensive understanding of the fluctuating, coherent flow structures attributable to various geometric details of landing gear. Through the advancement of knowledge in this area, it is expected that new techniques or methods will be developed to realize reductions in landing-gear noise compared to the present designs. This project is proposed in collaboration with Bombardier.