Mean Flow Features Around the Inline Wheels of Four-Wheel Landing Gear

Landing gear are noted to be a signie cant, sometimes dominant, airframe noise source for commercial aircraft. Aerodynamicnoiseis a directresultofthee uctuating e owand its interaction with surfacecomponents. Knowledge of the mean e ow, however, can be used to aid in the determination of noise sources. The complex geometry of multiple-wheel-set landing gear has thus far precluded even this basic information. In this study the mean e owe eld is determined in a streamwise plane surrounding the inline wheels of a generic four-wheel landing-gear cone guration using digital particle image velocimetry. The velocity and vorticity e elds highlight a vortex that persists between the wheels on the ground side of the axle midplane. The formation of this vortex is believed to resultfrom thegeometricasymmetry caused by the presenceofthecentersupportstrut.Evidenceis also presented that shows the vortex does not remain stationary, but oscillates between the fore and aft wheels. Its position is hypothesized to dependon thestateofan unstablevorticity layerthatdevelopson theground sideoftheforewheel.