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1.
We give an analytical analysis to the acoustic propagation in an acoustic diode (AD) model formed by coupling a superlattice (SL) with a nonlinear medium. Analytical solutions of the acoustic transmission are obtained by studying the propagations in the SL and the nonlinear medium separately with the conventional transfer-matrix method and a perturbation technique. Compared with the previous numerical method, the proposed approach contributes a better physical insight into the intrinsic mechanism of acoustic rectification and helps us to predict the performance of an AD within the effective rectifying bands in a simple way. This is potentially significant for the practical design and fabrication of AD devices. 相似文献
2.
Propagation of an acoustic wave in a soft medium permeated with air bubbles is theoretically investigated by using a self-consistent approach. The soft medium is assumed to be viscoelastic to estimate the effect of acoustic absorption on the acoustic localization in such a medium. The oscillation phases of bubbles are examined by employing a phase diagram method. A collective oscillation of the bubbles is observed once the acoustic localization occurs, which is known as a phenomenon of 'phase transition ', and such a phenomenon persists as we manually increase the viscosity factor of the soft medium. Therefore it is proven that the phenomenon of phase transition may serve as a unique criterion to effectively identify acoustic localization in a bubbly soft medium even in the presence of viscosity, and the directions of the phase vectors help to determine the extent of localization. This is of practical significance for experimental research studying the acoustic localization in such a medium, for which the presence of viscosity generally causes great ambiguity in distinguishing the effects of localization and acoustic absorption. 相似文献
3.
High-efficiency unidirectional wavefront manipulation for broadband airborne sound with a planar device
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In the past decade, one-way manipulation of sound has attracted rapidly growing attention with application potentials in a plethora of scenarios ranging from ultrasound imaging to noise control. Here we propose a design of a planar device capable of unidirectionally harnessing the transmitted wavefront for broadband airborne sound. Our mechanism is to use the broken spatial symmetry to give rise to different critical angles for plane waves incident along opposite directions. Along the positive direction, the incoming sound is allowed to pass with high efficiency and be arbitrarily molded into the desired shape while any reversed wave undergoes a total reflection. We analytically derive the working bandwidth and incident angle range, and present a practical implementation of our strategy. The performance of our proposed device is demonstrated both theoretically and numerically via distinct examples of production of broadband anomalous refraction, acoustic focusing and non-diffractive beams for forward transmitted wave while virtually blocking the reversed waves. Bearing advantages of simple design, planar profile, broad bandwidth and high efficiency, our design opens the possibility for novel one-way acoustic device and may have important impact on diverse applications in need of special control of airborne sound. 相似文献
4.
Fast prediction of aerodynamic noise induced by the flow around a cylinder based on deep neural network
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Hai-Yang Meng 《中国物理 B》2022,31(6):64305-064305
Accurate and fast prediction of aerodynamic noise has always been a research hotspot in fluid mechanics and aeroacoustics. The conventional prediction methods based on numerical simulation often demand huge computational resources, which are difficult to balance between accuracy and efficiency. Here, we present a data-driven deep neural network (DNN) method to realize fast aerodynamic noise prediction while maintaining accuracy. The proposed deep learning method can predict the spatial distributions of aerodynamic noise information under different working conditions. Based on the large eddy simulation turbulence model and the Ffowcs Williams-Hawkings acoustic analogy theory, a dataset composed of 1216 samples is established. With reference to the deep learning method, a DNN framework is proposed to map the relationship between spatial coordinates, inlet velocity and overall sound pressure level. The root-mean-square-errors of prediction are below 0.82 dB in the test dataset, and the directivity of aerodynamic noise predicted by the DNN framework are basically consistent with the numerical simulation. This work paves a novel way for fast prediction of aerodynamic noise with high accuracy and has application potential in acoustic field prediction. 相似文献
5.
Based on the modification of the radial pulsation equation
of an individual bubble, an effective medium method (EMM) is presented for
studying propagation of linear and nonlinear longitudinal acoustic waves
in viscoelastic medium permeated with air bubbles. A classical theory
developed previously by Gaunaurd (Gaunaurd GC and \"{U}berall H, {\em J.
Acoust. Soc. Am}., 1978; 63: 1699--1711) is employed to verify the EMM under linear approximation
by comparing the dynamic (i.e. frequency-dependent) effective parameters,
and an excellent agreement is obtained. The propagation of longitudinal
waves is hereby studied in detail. The results illustrate that the nonlinear
pulsation of bubbles serves as the source of second harmonic wave and the
sound energy has the tendency to be transferred to second harmonic wave.
Therefore the sound attenuation and acoustic nonlinearity of the
viscoelastic matrix are remarkably enhanced due to the system's resonance
induced by the existence of bubbles. 相似文献
6.
电子二极管的发明标志着现代电子学的诞生, 在整个人类社会中引起了科技的深刻变革. 声波是一种具有非常悠久的研究历史的经典波, 却始终被认为仅具有对称的传播形式. 若能制造出可像电子二极管控制电流般实现声波单向导通的声学器件, 显然将对整个声学研究领域产生重大影响, 具有重要的科学意义及应用价值. 第一个基于非线性媒质与声子晶体的声二极管利用非线性突破声学互易原理的局限, 首次实现了将声能流限制在单一方向上的声整流效应. 针对非线性系统转换效率低下的固有缺陷, 在线性体系内围绕声单向传播这个重要科学问题开展了一系列理论和实验研究, 设计与制备了多种具有特殊结构和性能的线性声学单向结构, 在器件的效率、带宽及尺寸方面产生了突破. 在声二极管研究的基础上, 第一个可以像电子三极管操控电流般对声流进行操控与放大的声三极管理论模型也被提出. 本文介绍了声单向传播这一新兴且富有蓬勃生机的研究领域中的主要进展. 相似文献
7.
The propagation of longitudinal acoustic waves in weakly compressible elastic media permeated with air bubbles is investigated on the basis of the radial pulsation equation of a single bubble. The multiple scattering of waves in such media is rigorously described by using a self-consistent approach. Theoretical results show that there exists strong acoustic localization in a range of frequency slightly above the bubble resonance frequency, even for a very small volume fraction of bubbles. Further study reveals that the localization is in fact attributed to collection behaviour of bubbles, allowing for an efficient cancellation of propagating waves. This is essentially consistent with the known conclusions recently drawn for bubbly liquid by Kou et al. [2003 Appl. Phys. Left. 83 4247] 相似文献
8.
Based on fuzzy logic (FL) and genetic algorithm (GA), we present an optimization method to obtain the optimal acoustic attenuation of a longitudinal acoustic wave propagating in a weakly compressible medium permeated with air bubbles. In the optimization, the parameters of the size distribution of bubbles in the medium are optimized for providing uniformly high acoustic attenuation in the frequency band of interest. Compared with other traditional optimization methods, the unique advantage of the present method is that it can locate the global optimum quickly and effectively in need of knowing the mathematical model precisely. As illustrated by a numerical simulation, the method is effective and essential in enhancing the acoustic attenuation of such a medium in an optimal manner. The bubbly medium with optimized structural parameters can effectively attenuate longitudinal waves at intermediate frequencies with an acoustic attenuation approximating a constant value of lO(dB/cm). Such bubbly media with optimal acoustic attenuations may be applied to design acoustic absorbent by controlling broader attenuation band and higher efficiency. 相似文献
9.
作为第一个可实现电整流的器件,电子二极管的发明标志着现代电子学的诞生,并在全球范围内引发了各个领域内的革命,最终深刻地改变了我们的整个生活.声波作为一种重要的经典波,具有比电磁波更为悠久的研究历史及更为普遍的存在形式.因此,若能设计并实现一种可像电子二极管控制电流那样对声能量进行整流的声学器件,这将对声学的器件制造、实际应用乃至整个声学研究领域都产生重大影响,其学术意义及应用价值的重要性不言而喻.文章详细介绍了利用超晶格与非线性声学材料构成的声二极管的理论与实验方面的最新研究进展. 相似文献
10.