Amplitude and frequency characteristics of acoustic jets

The prerequisites to formation and the characteristics of a jet that occurs at the open end of a waveguide guiding an intense sound wave are studied. The velocity field is measured by a hot-wire anemometer. The previously developed method of separating the jet velocity V_jet from the amplitude of the oscillating particle velocity V_osc, which is applicable only when V_jet>V_osc, is supplemented with the method of oscillogram processing applicable for V_jet≤V_osc. Thus, a full picture of the jet evolution in space, starting from the waveguide outlet, is obtained. The experimentally determined spatial distribution of the jet velocity is found to agree well with the numerically simulated dependences reported by other authors. For the oscillating velocity amplitude at the open end of the waveguide, a threshold value, beyond which the formation of the acoustic jet takes place, is revealed. The frequency dependence of this threshold value is determined. The dependence of the maximal jet velocity on the oscillating velocity amplitude in the outlet waveguide cross section is found to be close to linear.