Noise suppression mechanism of flow in annular cavity using annular groove at subsonic speeds

To investigate the mechanism of noise reduction of landing gear hubs, the noise suppression effect and mechanism of an annular groove (simplification of an annular wheel hub rim) on an annular cavity (simplification of an annular wheel hub) have been studied computationally using the Detached Eddy Simulation method combined with the Ffowcs Williams-Hawkings acoustic analogy in this paper. The Mach number of the freestream is from 0.13 to 0.21. The results demonstrated that the annular groove alters the boundary layer profile in the vicinity of the annular cavity. This causes the kinetic energy within the boundary layer to move towards the upper boundary layer, the boundary layer displacement thickness to increase, and the flow mass loss to increase. Concurrently, the annular groove results in a reduction in shear layer flow velocity, thereby weakening the interaction of the flow with the center cylinder (simplification of a wheel axle), the rear-edge and the internal wall of the annular cavity, reducing the velocity fluctuation and the turbulent kinetic energy near the annular cavity walls. This suppresses the intensity of flow-acoustic feedback noise, while simultaneously suppresses the intensity of both the acoustic feedback noise and the turbulent broadband noise.