Recent advances in investigation on jet fluctuation and radiated sound in flute-like instruments

In this talk, we review our previous research on flow and sound in flute-like instruments and report on our ongoing research. First, we explain the modified version of Fletcher's formula (N. H. Fletcher, JASA, 60(4), 926–936, 1976) representing the jet fluctuations proposed based on direct aerodynamic simulations for recorders (K. Onogi et al., JASA, 146, 1427−1437, 2019). This formula newly takes into account the deflection of jet and was utilized to quantitatively compare the jet fluctuations in two recorders with different geometries around the windway and edge. Next, we report recent findings on the effects of the jet angle (the angle between the jet and the mouth opening surface) in flute blowing. As the jet angle was increased (the jet is directed perpendicular to the mouth opening), the radiation of the second harmonic was intensified more than that of the third harmonic, and the measurements with a hot-wire anemometer observed that the jet was deflected toward the inside of the pipe (K. Onogi et al., Acta Acust., 5(11), 2021). We discuss the mechanism of jet deflection and its relationship with the radiated sound, based on results from direct aerodynamic simulations for a flute.