Numerical Simulation of Aerodynamics Sound in an Ocarina Model

Hiroaki Okadaa, Sho Iwagamia, Taizo Kobayashib and Kin'Ya Takahashia

aKyushu Institute of Technology
bKyushu University

Sunday, September 15, 2019 from 09:40 to 10:00

in Summer Theater

Abstract :
The body of an ocarina is regarded as a Helmholtz resonator. Thus, we can expect differences in sounding mechanism between ocarinas and other air-jet instruments with a resonance pipe. Furthermore, ocarinas are driven by cross blowing like transverse flutes so that the driving mechanism with an air-jet should be different from that for vertical flues like a recorder. In this paper, we numerically explore the sounding mechanism of an ocarina from the view point of aeroacoustics with compressible fluid simulation. We adopt compressible LES as a numerical scheme of compressible fluid, which simultaneously reproduces fluid and acoustic fields and with which we can investigate the interaction between the fluid and acoustic fields near the mouth opening. Our 3D model has numerical grids more than one hundred and 50 million to reproduce detail behavior of air-jet motion, vortices and acoustic filed near the mouth opening. We numerically observed an acoustic oscillation with the Helmholtz resonance frequency in the body together with the detail structure of fluid field.

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