音波による2次元水噴流の挙動

Abstract

In the previous paper, the relation between the behaviour of two-dimensional water jets affected by sound and the decay of velocity fluctuations has been discussed in the sensitive region by using Taylor's statistical theory of turbulence. As a result, especially, it has been proved that the behaviour of a sound-sensitive water jet is related to the decay of velocity fluctuations in the downstream side of the transition domain from a laminar jet to a turbulent jet.In this paper, the behaviour of velocity fluctuations in a two-dimensional water jet sensitive to sound. is experimentally investigated by using spectrum analysis and correlation technique. Especially, the slope of the decay of velocity fluctuations in the flow direction is obtained by using Taylor's statistical theory and is compared with the experimental results.The following facts are confirmed:1) From the tendency of turbulent intensity, a sound-sensitive water jet is devided into three domains: the laminar, transition, and turbulent domains.2) In the laminar domain, the velocity fluctuations produced by sound propagate and grow exponentially in the flow direction depending on the sound frequency.3) In the transition domain, two nonlinear interactions of velocity fluctuations take place: the production of components of other frequencies and the suppression of the growth of several marked components.4) The behaviour of a sound-sensitive water jet is related to both the decay and the nonlinear interaction of velocity fluctuations.