Acoustic Control of Turbulent Jets

Development of turbulence in subsonic submerged jets

“…Moreover, it follows from our theory that the commonly accepted [60][61][62][63][64][65]21,4] explanation for the well-known shift of velocity pulsation power spectra towards the low-frequency region is in fact erroneous. According to this explanation, the shift of the power spectra occurs because of feedback via an acoustic wave nascent where vortex pairing occurs, as seen in experiments.…”

“…The harmonic disturbance plays a dual role. First, it causes the appearance of instability and, secondly, it initiates the phase transition, much as occurs in a pendulum with a randomly vibrated suspension axis [58], or in jets under low-frequency acoustic forcing [4]. It is no accident that the transition to turbulence was observed by Nikitin only for low-frequency disturbances (for Strouhal numbers of order 0.1).…”

“…For such a system to become self-oscillatory, global feedback must be introduced, e.g. by closing the system in a ring 4 . Disturbances are necessarily present in all real systems, both from external sources (technical fluctuations) and as a result of the molecular structure of a substance (natural fluctuations).…”

“…An extremely interesting manifestation of nonlinear effects in jets lies in the possibility of exploiting them to control turbulence with the aid of acoustic waves applied at some appropriate frequency ( [4,[52][53][54][55][56][57]. Similar control of noise-induced oscillations was demonstrated for the harmonically driven pendulum [58,51].…”

“…Over the years the volume of experimental works has increased to such an extent that it cannot even be listed in a review of this kind. As examples, we mention only a fundamental paper by Reynolds [2], where elegant experiments with stained liquid were described and intermittent behavior was first discovered, the Compte-Bellot's book [3], wherein a detailed comparison is made between turbulence power spectra in a plane channel and Kolmogorov's spectra, and the book by Ginevsky et al [4] in which experiments with jets are reviewed. A wide variety of books is devoted to the problem of hydrodynamic instability playing the major role in the transition to turbulence (see, e.g.…”