Haoyang Zhang

Remote signal amplification in parametric acoustic receiving array using the Mathieu type oscillator

In this paper, a new remote periodic signal detection method in water, utilizing the combination of the parametric acoustic receiving array and the Mathieu type parametric oscillator is proposed. In order to amplify the remote signal in the parametric acoustic receiving array, the received cross-modulated signal which contains pump frequency and side frequency components is imported into the Mathieu type parametric excited oscillator. The method of electro-acoustical analogy is employed to generate the cross-modulated signal of the parametric receiving array. Arising from the basic equations which are valid for the media of quadratic nonlinearity, the equivalent travelling-wave circuits that describe the nonlinear interaction of multi-frequency acoustic waves are obtained. Furthermore, the dynamics of the Mathieu oscillator in the cases of parametric resonance is studied. Due to the parametric resonance state of the oscillator, it is determined that the remote signal can be significantly amplified when parametric resonance occurs. The proposed method is compared with the traditional parametric receiving one, which is analyzed equally in amplification gain and signal-noise ratio.In this paper, a new remote periodic signal detection method in water, utilizing the combination of the parametric acoustic receiving array and the Mathieu type parametric oscillator is proposed. In order to amplify the remote signal in the parametric acoustic receiving array, the received cross-modulated signal which contains pump frequency and side frequency components is imported into the Mathieu type parametric excited oscillator. The method of electro-acoustical analogy is employed to generate the cross-modulated signal of the parametric receiving array. Arising from the basic equations which are valid for the media of quadratic nonlinearity, the equivalent travelling-wave circuits that describe the nonlinear interaction of multi-frequency acoustic waves are obtained. Furthermore, the dynamics of the Mathieu oscillator in the cases of parametric resonance is studied. Due to the parametric resonance state of the oscillator, it is determined that the remote signal can be significantly amplified when pa...

Research on the influence of dispersion in the shallow water waveguide on the parametric array

In practice, the application of parametric array is limited due to the effect of dispersion in the shallow water waveguide which has a significant impact on the propagation of the difference frequency wave. This paper attempts to provide better understanding of the difference frequency field in the shallow water waveguide by discussing the virtue source of parametric array in such circumstance. In the paper, the Green’s function of the shallow water waveguide is employed for calculating the difference frequency field with the help of virtue source in waveguide. It shows that the wavenumber mismatch caused by waveguide dispersion will restrain the accumulation of difference frequency wave and bring about fluctuations during the process of accumulation. Furthermore, this paper discusses the nonlinear interaction with different modes of pump wave based on the former conclusion and reveals pictures to describe the complicated mode structure of the difference frequency field.

Beam characteristics of the truncated parametric array generated by a panel piston radiator

A theoretical model is presented to describe the difference frequency beam characteristics of the truncated parametric array generated by a panel piston radiator. In this model, a low-pass acoustic filter is used to truncate the virtual-source. The truncated virtual-source can be viewed as a volume distributed cylindrical source and conic source within and beyond the Rayleigh distance, respectively. The difference frequency beam characteristics near the truncated position are significantly changed. Numerical simulation results show that the difference frequency beams near the truncated position are substantially sharpened with the distance between the observation point and the truncated position decreasing. Besides, the difference frequency beamwidth near the truncated position can be used to predict the farfield beamwidth of the truncated parametric array.

Bubble nonlinear dynamics and stimulated scattering process

A complete understanding of the bubble dynamics is deemed necessary in order to achieve their full potential applications in industry and medicine. For this purpose it is first needed to expand our knowledge of a single bubble behavior under different possible conditions including the frequency and pressure variations of the sound field. In addition, stimulated scattering of sound on a bubble is a special effect in sound field, and its characteristics are associated with bubble oscillation mode. A bubble in liquid can be considered as a representative example of nonlinear dynamical system theory with its resonance, and its dynamics characteristics can be described by the Keller–Miksis equation. The nonlinear dynamics of an acoustically excited gas bubble in water is investigated by using theoretical and numerical analysis methods. Our results show its strongly nonlinear behavior with respect to the pressure amplitude and excitation frequency as the control parameters, and give an intuitive insight into stimulated sound scattering on a bubble. It is seen that the stimulated sound scattering is different from common dynamical behaviors, such as bifurcation and chaos, which is the result of the nonlinear resonance of a bubble under the excitation of a high amplitude acoustic sound wave essentially. The numerical analysis results show that the threshold of stimulated sound scattering is smaller than those of bifurcation and chaos in the common condition.

Analogy between the one-dimensional acoustic waveguide and the electrical transmission line in the cases of nonlinearity and relaxation

The propagation of plane acoustic waves can be investigated by taking advantage of the electro-acoustical analogy between the one-dimensional acoustic waveguide and the electrical transmission line, because they share the same type of equation. This paper follow the previous studies and expand the analogy into the cases of quadratic nonlinearity and dispersion produced by relaxation process. From the basic equations relating acoustic pressure, density fluctuation and velocity, which are valid for the nonlinear and relaxing media, the equivalent travelling-wave circuits of one-dimensional acoustic waveguide with the consideration of nonlinearity and relaxation processes are obtained. Furthermore, we also discuss the analogy relationship of parameters which exist in the acoustical and electrical systems.

Acoustic characteristics of the medium with gradient change of impedance

The medium with gradient change of acoustic impedance is a new acoustic structure which developed from multiple layer structures. In this paper, the inclusion is introduced and a new set of equations is developed. It can obtain better acoustic properties based on the medium with gradient change of acoustic impedance. Theoretical formulation has been systematically addressed which demonstrates how the idea of utilizing this method. The sound reflection and absorption coefficients were obtained. At last, the validity and the correctness of this method are assessed by simulations. The results show that appropriate design of parameters of the medium can improve underwater acoustic properties.

Numerical investigation of bubble nonlinear dynamics characteristics

The complicated dynamical behaviors of bubble oscillation driven by acoustic wave can provide favorable conditions for many engineering applications. On the basis of Keller-Miksis model, the influences of control parameters, including acoustic frequency, acoustic pressure and radius of gas bubble, are discussed by utilizing various numerical analysis methods, Furthermore, the law of power spectral variation is studied. It is shown that the complicated dynamic behaviors of bubble oscillation driven by acoustic wave, such as bifurcation and chaos, further the stimulated scattering processes are revealed.

Bubble nonlinear oscillation in a sound field

The complicated mechanism of gas bubble oscillation in a sound field is quite fascinating. Based on the Keller-Miksis model, a deliberate numerical investigation of the nonlinear radial oscillations of a gas bubble driven by finite-amplitude waves is presented. Some crucial control parameters of the bubble radial oscillations, including the bubble equilibrium radius, acoustic frequency and acoustic pressure, are studied with multiple numerical analysis methods. Parameter regions which are beneficial for complex dynamic properties are given. Its found that there is an excitation amplitude threshold varying with excitation frequency for the occurrence of bifurcation and chaos. The chaotic regions are discontinuous in the parts with small acoustic amplitude and normalized frequency and continuous in the parts with both large amplitude and high frequency. Moreover, larger excitation amplitude is corresponding to more vigorous chaotic degree with broader chaotic region in frequency range.

Theory and experiment of the resonance sound wave interactions in water

Equations governing nonlinear interactions among acoustic waves in water which satisfy the resonance conditions are derived from the Burgers equation. Taking into account of the second-order nonlinear, the three-wave interaction is the fundamental process of the interaction equations. Then, taking the three-wave interaction equation as an example, the energy transfer mechanism among the three acoustic waves is quantitatively analyzed. And the three-wave sound energy propagation is studied through numerical calculation. An interesting phenomenon is found that, when the three acoustic waves meet the relationship of a weak low-frequency sound and two strong high-frequency sounds, the energy of low-frequency sound will be amplified or reduced in some regions during the three-wave propagation. And the location and size of the regions are affected by the acoustic wave amplitude, frequency, and phase. The variation severities of low-frequency acoustic wave energy are mainly determined by other two high-frequency...

An equivalent physical model of three acoustic waves interaction in nonlinear medium

Among the parametric effects, three waves interaction has been widely investigated in many fields of physics, such as nonlinear optics and plasma. The interaction of three acoustic waves in the medium with quadratic nonlinearity, which must satisfy conditions on their frequencies and wavenumbers, is essentially confined to energy exchange between three components. Based on Burgers equation, the propagation rules of three acoustic waves, which are called a resonant triad, are governed by a drastically simplified system of three coupled nonlinear ordinary differential equations. A mathematical equivalence between the equations for an acoustic triad and a simple parametric vibration system, the undamped elastic pendulum, is discussed in this paper by a multiple time-scale analysis. We study the dynamics of this system, drawing analogies between its behavior and that of the acoustic triad. Finally, it is certified that three acoustic waves interaction can be described by Mathieu type equations in case one acoustic wave is much stronger than the others in three waves. This means that experiments with an elastic pendulum can give us new insights into dynamics of mechanism in three acoustic waves interaction.