Sound generation in flutelike instruments: Simulation and analysis
Helmut Kuehnelt · The Journal of the Acoustical Society of America · 2006
Three-dimensional flow-acoustic simulations using the lattice Boltzmann method were used to study the sound generation in flutes and recorders. Theory suggests that the fluctuating Coriolis force in the mouth of the instrument caused by the fluctuating vorticity distribution of the jet is the main source of sound. A numerical experiment was undertaken to clarify this hypothesis for flute instruments. In the mouth of the instrument an equivalent temporal fluctuating force was imposed in a quiescent fluid. Although this force excited fluid dynamic effects in the mouth not present at mean flow, it nevertheless induced a standing wave in the instrument with a sound pressure whose amplitude differed only less than 1 dB from the playing situation. This shows the cardinal role of the Coriolis force for the sound generation in flutes. The temporal and spatial structure of the Coriolis force distribution and the vortex sound power generated will be compared for flute and recorder. Especially the spatial structure differs systematically for the two types of instruments. Implications for the design of flute head joints will be discussed.