Nonlinear generation of non-acoustic modes by low-frequency sound in a vibrationally relaxing gas

2010 ◽  
Vol 88 (4) ◽  
pp. 293-300 ◽  
Author(s):  
Anna Perelomova
Keyword(s):  
Degrees Of Freedom ◽  
Vibrational Energy ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Dynamic Equations ◽  
Thermal Mode ◽  
Acoustic Source ◽  
Frequency Sound ◽  
Acoustic Modes ◽  
Relaxing Gas

Two dynamic equations referring to a weakly nonlinear and weakly dispersive flow of a gas in which molecular vibrational relaxation takes place, are derived. The first one governs an excess temperature associated with the thermal mode, and the second one describes variations in vibrational energy. Both quantities refer to non-wave types of gas motion. These variations are caused by the nonlinear transfer of acoustic energy into thermal mode and internal vibrational degrees of freedom of a relaxing gas. The final dynamic equations are instantaneous; they include a quadratic nonlinear acoustic source, reflecting the nonlinear character of interaction of low-frequency acoustic and non-acoustic motions of the fluid. All types of sound, periodic or aperiodic, may serve as an acoustic source of both phenomena. The low-frequency sound is considered in this study. Some conclusions about temporal behavior of non-acoustic modes caused by periodic and aperiodic sound are made. Under certain conditions, acoustic cooling takes place instead of heating .

Nonlinear Influence of Sound on the Vibrational Energy of Molecules in a Relaxing Gas

2012 ◽  
Vol 37 (1) ◽  
pp. 89-96 ◽  
Author(s):  
Anna Perelomova
Keyword(s):  
High Frequency ◽  
Degrees Of Freedom ◽  
Vibrational Energy ◽  
Acoustic Energy ◽  
Acoustic Source ◽  
Weakly Nonlinear ◽  
Dispersive Flow ◽  
Nonlinear Character ◽  
Nonlinear Acoustic ◽  
Relaxing Gas

AbstractDynamics of a weakly nonlinear and weakly dispersive flow of a gas where molecular vibrational relaxation takes place is studied. Variations in the vibrational energy in the field of intense sound is considered. These variations are caused by a nonlinear transfer of the acoustic energy into energy of vibrational degrees of freedom in a relaxing gas. The final dynamic equation which describes this is instantaneous, it includes a quadratic nonlinear acoustic source reflecting the nonlinear character of interaction of high-frequency acoustic and non-acoustic motions in a gas. All types of sound, periodic or aperiodic, may serve as an acoustic source. Some conclusions about temporal behavior of the vibrational mode caused by periodic and aperiodic sounds are made.

Using Time-Periodicity for Inducing Energy Transfer Between Vibration Modes

2013 ◽  
Author(s):  
Fadi Dohnal ◽  
Aleš Tondl
Keyword(s):  
Energy Transfer ◽  
Degrees Of Freedom ◽  
Vibrational Energy ◽  
Low Frequency ◽  
Vibration Modes ◽  
Present Contribution ◽  
Multiple Degrees Of Freedom ◽  
Time Periodicity ◽  
The Many ◽  
And Control

Introducing time-periodicity in system parameters may lead, in general, to a dangerous and well-known parametric resonance. In contrast to such a resonance, a properly tuned time-periodicity is capable of transferring energy between vibration modes. Time-periodicity in combination with system damping is capable of efficiently extracting vibrational energy from the system and of amplifying the existing damping affecting transient vibrations. Operating the system at such a specific time-periodicity, the system is tuned at a parametric anti-resonance. The basic principle of this concept has been studied theoretically and was proven experimentally. The physical interpretation of this concept was proposed in “Damping by Parametric Stiffness Excitation: Resonance and Anti-Resonance”, Journal of Vibration and Control, 2008, for a multiple degrees of freedom system. The present contribution highlights those findings on a multiple degrees of freedom system. It is illustrated that a parametric anti-resonance is connected to inducing an energy transfer between two of the many vibration modes of the underlying system with constant coefficients. The induced energy transfer can be utilized to transfer the vibration energy from low frequency to high frequency or vice versa or, in case of system damping, to a more efficient dissipation of vibrational energy. The achievable energy dissipation is most significant if an energy transfer is induced between a lightly damped mode and a strongly damped mode.

The nonlinear effects of sound in a liquid with relaxation losses

2015 ◽  
Vol 93 (11) ◽  
pp. 1391-1396
Author(s):  
Anna Perelomova
Keyword(s):  
Chemical Reaction ◽  
High Frequency ◽  
Low Frequency ◽  
Nonlinear Effects ◽  
Dynamic Equations ◽  
High Frequency Sound ◽  
Frequency Sound ◽  
Relaxation Modes ◽  
The Difference ◽  
Wave Modes

The nonlinear effects of sound in electrolyte with a chemical reaction are examined. The dynamic equations that govern non-wave modes in the field of intense sound are derived, and acoustic forces of vortex, entropy, and relaxation modes are determined in the cases of low-frequency sound and high-frequency sound. The difference in the nonlinear effects of sound in electrolyte and in a gas with excited vibrational degrees of molecules, are specified and discussed.

scholarly journals A Pendulum-Like Low Frequency Electromagnetic Vibration Energy Harvester Based on Polymer Spring and Coils

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3380
Author(s):  
Yunjia Li ◽  
Xinyi Wang ◽  
Shuhan Zhang ◽  
Chenyuan Zhou ◽  
Dayong Qiao ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Output Voltage ◽  
Degrees Of Freedom ◽  
Energy Harvester ◽  
Vibrational Energy ◽  
Low Frequency ◽  
Open Circuit ◽  
Vibration Energy ◽  
Vibration Energy Harvester ◽  
Circuit Output

This paper presents a low-frequency electromagnetic vibrational energy harvester (EVEH) with two degrees of freedom and two resonant modes. The proposed EVEH is based on a disc magnet suspended in a pendulum fashion by a polymeric spring between two sets of polymer coil stacks. The fabricated EVEH is capable of harvesting vibration energy on two directions with an extended bandwidth. With a sinusoidal acceleration of ±1 g on Z direction, a peak-to-peak closed-circuit output voltage of 0.51 V (open-circuit voltage: 1 V), and an output power of 35.1 μW are achieved at the resonant frequency of 16 Hz. With a sinusoidal acceleration of ±1.5 g on X direction, a peak-to-peak output voltage of 0.14 V and power of 2.56 μW are achieved, at the resonant frequency of 20 Hz.

Features of Nonlinear Sound Propagation in Vibrationally Excited Gases

2013 ◽  
Vol 38 (3) ◽  
pp. 357-362
Author(s):  
Anna Perelomova ◽  
Magdalena Kusmirek
Keyword(s):  
High Frequency ◽  
Degrees Of Freedom ◽  
Sound Propagation ◽  
Vibrational Excitation ◽  
Low Frequency ◽  
Vibrationally Excited ◽  
Weakly Nonlinear ◽  
High Frequency Sound ◽  
Frequency Sound ◽  
Nonlinear Distortions

Abstract Weakly nonlinear sound propagation in a gas where molecular vibrational relaxation takes place is studied. New equations which govern the sound in media where the irreversible relaxation may take place are derived and discussed. Their form depends on the regime of excitation of oscillatory degrees of freedom, equilibrium (reversible) or non-equilibrium (irreversible), and on the comparative frequency of the sound in relation to the inverse time of relaxation. Additional nonlinear terms increase standard nonlinearity of the high-frequency sound in the equilibrium regime of vibrational excitation and decrease otherwise. As for the nonlinearity of the low-frequency sound, the conclusions are opposite. Appearance of a non-oscillating additional part which is a linear function of the distance from the transducer is an unusual property of nonlinear distortions of harmonic at the transducer high-frequency sound

scholarly journals Study on broadband low-frequency sound insulation of multi-channel resonator acoustic metamaterials

AIP Advances ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 045321
Author(s):  
Chi Xu ◽  
Hui Guo ◽  
Yinghang Chen ◽  
Xiaori Dong ◽  
Hongling Ye ◽  
...  
Keyword(s):  
Low Frequency ◽  
Sound Insulation ◽  
Acoustic Metamaterials ◽  
Frequency Sound
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