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Register a new userCoupled-Mode Theory for Stationary and Nonstationary Resonant Sound Propagation
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We present a complete analytical derivation of the equations used for stationary and nonstationary wave systems regarding resonant sound transmission and reflection described by the phenomenological Coupled-Mode Theory. We calculate the propagating and coupling parameters used in Coupled-Mode Theory directly by utilizing the generalized eigenwave-eigenvalue problem from the Hamiltonian of the sound wave equations. This Hamiltonian formalization can be very useful since it has the ability to describe mathematically a broad range of acoustic wave phenomena. We demonstrate how to use this theory as a basis for perturbative analysis of more complex resonant scattering scenarios. In particular, we also form the effective Hamiltonian and coupled-mode parameters for the study of sound resonators with background moving media. Finally, we provide a comparison between Coupled-Mode theory and full-wave numerical examples, which validate the Hamiltonian approach as a relevant model to compute the scattering characteristics of waves by complex resonant systems.
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A mode parabolic equation method for resonantly interacted modes was developed. The flow of acoustic energy is conserved for the derived equations with an accuracy adequate to the used approximation. The testing calculations were done for ASA wedge benchmark and proved excellent agreement with COUPLE program.
Coupled mode theory (CMT) is a powerful framework for decomposing interactions between electromagnetic waves and scattering bodies into resonances and their couplings with power-carrying channels. It has widespread use in few-resonance, weakly coupled resonator systems across nanophotonics, but cannot be applied to the complex scatterers of emerging importance. We use quasinormal modes to develop an exact, ab initio generalized coupled mode theory from Maxwells equations. This quasinormal coupled mode theory, which we denote QCMT, enables a direct, mode-based construction of scattering matrices without resorting to external solvers or data. We consider canonical scattering bodies, for which we show that a CMT model will necessarily be highly inaccurate, whereas QCMT exhibits near-perfect accuracy.
A pure analytic one-way coupled mode propagation model for resonant interacting modes is obtained by the multiscale expansion method. It is proved that the acoustic energy flux is conserved in this model up to the first degree of the corresponding small parameter. The test calculations with the COUPLE program give an excellent agreement.
Electromagnetic (EM) scattering systems widely exist in EM engineering domain. For a certain objective scattering system, all of its working modes constitute a linear space, i.e. modal space. Characteristic mode theory (CMT) can effectively construct a basis of the space, i.e. characteristic modes (CMs), and the CMs only depend on the inherent physical properties of the objective system, such as the topological structure and the material parameter of the objective system. Thus, CMT is very valuable for analyzing and designing the inherent EM scattering characters of the objective system. This work finds out that integral equation (IE) is not the best framework for carrying CMT. This dissertation proposes a completely new framework for carrying CMT, i.e. work-energy principle (WEP) framework, and at the same time proposes a completely new method for constructing CMs, i.e. orthogonalizing driving power operator (DPO) method. In new WEP framework and based on new orthogonalizing DPO method, this work resolves 5 pairs of important unsolved problems existing in CMT domain.
Acoustic cloaks that make object undetectable to sound waves have potential applications in a variety of scenarios and have received increasing interests recently. However, the experimental realization of a three-dimensional (3D) acoustic cloak that works within broad ranges of operating frequency and incident angle still remains a challenge despite the paramount importance for the practical application of cloaking devices. Here we report the design and experimental demonstration of the first 3D broadband cloak capable of cancelling the scattering field near curved surfaces. Unlike the ground cloaks that only work in the presence of a flat boundary, the proposed scheme can render the invisibility effect for an arbitrarily curved boundary. The designed cloak simply comprises homogeneous positive-index anisotropic materials, with parameters completely independent of either the cloaked object or the boundary. With the flexibility of applying to arbitrary boundaries and the potential of being extended to yield 3D acoustic illusion effects, our method may take major a step toward the application of acoustic cloaks in reality and open the avenue to build other acoustic devices with versatile functionalities.
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