Chaos and beyond in a water filled ultrasonic resonance system

Finite amplitude ultrasonic wave resonances in a one dimensional liquid-filled cavity are reported. The resonances are observed to include not only the expected harmonic and subharmonic signals but chaotic signals as well. The nonlinear features of this system were recently investigated and are the focus of this presentation. An ultrasonic interferometer having optical precision was constructed. The transducers having the frequency range 1-10 MHz, driven by a high power amplifier. Both an optical diffraction system and a receiving transducer were used to assess the generated resonance response in the cavity. Five regions of excitation are identified: 1. Linear region: at low intensity of the ultrasonic wave the diffraction pattern of a light beam is symmetric. 2. Nonlinear region: with increased sound amplitude the diffraction pattern becomes asymmetrical. 3. Subharmonic region: further increase of the amplitude above a threshold value leads to the generation of subharmonics. 4. Chaos: increasing the drive amplitude to a second threshold level the diffraction pattern is smeared out indicating a time-chaotic region. 5. Beyond chaos: further increase of the amplitude results again a stable diffraction pattern. A first-principle-based explanation is presented. This work is supported by the Aircraft Aging Program, at NASA Langley Research Center.