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. Author manuscript; available in PMC: 2019 Jul 11.
Published in final edited form as: J Acoust Soc Am. 2005 Jul;118(1):410–427. doi: 10.1121/1.1862251

FIG. 10.

FIG. 10

Aeroacustic source spectrum S(f) as a function of σΦ . Because S(f) is the spectrum of a single vortex filtered by the arrival function spectrum I(f), the statistics of the vortex ring arrival determine the character of the source spectrum. S(f) ―; I(f)-·-·, W(f) ---. (a) For σΦ⪡1, the jet is periodic, and I(f) exhibits tonal behavior, with tone levels modulated by shape of (W(f), reflecting both vortex path and wall shape. (b) For σΦ⊢1, I(f) is broad enough (flow is highly turbulent) that the shape of W(f) limits the shape of the source spectrum. In this case, the wall shape and vortex path dominate behavior of S(f).