Abstract
Sound source localization technology is used to study the noise mechanism generated by flow around a circular cylinder. Detached-eddy simulation is performed to compute the flow field and the far-field noise is calculated with the Ffowcs Williams and Hawkings acoustic analogy. At first the simulation method is validated with the flow around circular cylinder at Re=3900. The numerical results are compared with the experimental data by other researchers. The following case is to simulate the flow around circular cylinder at Re=46000. The acoustic result is found in good agreement with the experimental measurements. The acoustic analogy result is used as an input for the noise localization process. Microphone array technique is applied to investigate sound generated by flow around a circular cylinder with emphasis on sound generation mechanism. Two sound source localization methods are considered, including Delay-and-Sum beamforming algorithm and a high resolution beamforming method. The sound source is associated with the lift dipole at the vortex shedding frequency. The sound source is associated with the drag dipole at the double vortex shedding frequency. The sound source can also be shown at other frequency. With frequency increasing, the strength reduces and there are some other sidelobe sources.
Highlights
As aircraft engine noise decreases, landing gear noise is the main source of noise for the aircraft during the approach or landing
Flow around cylindrical is the basic model of landing gear noise, so the study of the acoustic emission around the cylinder has some enlightenment on the noise reduction of landing gear
The vortex shedding frequency is about 83Hz at this experimental condition, and it is so low that the microphone array resolution cannot identify the sound source location
Summary
As aircraft engine noise decreases, landing gear noise is the main source of noise for the aircraft during the approach or landing. Flow around cylindrical is the basic model of landing gear noise, so the study of the acoustic emission around the cylinder has some enlightenment on the noise reduction of landing gear. Many researchers are very interested in the flow around the cylinder. Strouhal measured the tones produced by flow around the cylinder. It can be said that flow around the cylinder include the boundary layer transition, flow separation, wake turbulence and so on.[1]
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