Browsing by Author "Ostrovsky, Lev A."
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Item Low-frequency acoustic wave generation in a resonant bubble layer(The Journal of the Acoustical Society of America, 1996-12) Druzhinin, Oleg A.; Ostrovsky, Lev A.; Prosperetti, AndreaThe nonlinear response of a bubble layer subject to harmonic and biharmonic excitation at frequencies smaller than the individual bubble resonance frequency is considered. The nonlinear resonance properties of the layer and generation of difference?frequency signal are studied analytically and numerically. It is found that, for bubble volume fractions ??10?3 and pump amplitudes of the order of 10?1 atm, the power of the low?frequency signal (including waves radiated in both directions) may reach 10% of the total power of the incident biharmonic wave. The efficiency is restricted by the rapid formation of shocks already at relatively low driving amplitudes, which may not occur in a more complete model accounting for the inertia of the bubble pulsations.Item Nonlinear wave interactions in bubble layers(The Journal of the Acoustical Society of America, 3/1/2003) Karpov, Sergey; Prosperetti, Andrea; Ostrovsky, Lev A.Due to the large compressibility of gas bubbles, layers of a bubbly liquid surrounded by pure liquid exhibit many resonances that can give rise to a strongly nonlinear behavior even for relatively low-level excitation. In an earlier paper [Druzhinin et al., J. Acoust. Soc. Am. 100, 3570 (1996)] it was pointed out that, by exciting the bubbly layer in correspondence of two resonant modes, so chosen that the difference frequency also corresponds to a resonant mode, it might be possible to achieve an efficient parametric generation of a low-frequency signal. The earlier work made use of a simplified model for the bubbly liquid that ignored the dissipation and dispersion introduced by the bubbles. Here a more realistic description of the bubble behavior is used to study the nonlinear oscillations of a bubble layer under both single- and dual-frequency excitation. It is found that a difference-frequency power of the order of 1% can be generated with incident pressure amplitudes of the order of 50 kPa or so. It appears that similar phenomena would occur in other systems, such as porous waterlike or rubberlike media.