Abstract
A corrugated tube open at both ends, with air flowing through it, emits sounds whose frequencies depend on the flow velocity and the length of the tube. The sounds it emits are the natural harmonics of the tube. Wind-tunnel experiments show that the sounds are excited by the impinging-shear-layer instability that occurs in the flow over the corrugations. The resulting instability is characterized by a self-excited resonant oscillation occurring in the fluid-acoustic coupled system.
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