arXiv subjects

V. Romero-García

Publications and source records attributed to V. Romero-García.

22 records · Page 2Linked to original sources

arXiv2011

Analytical model to predict the effect of a finite impedance surface on the propagation properties of a 2D Sonic Crystal

The use of Sonic Crystals as environmental noise barriers has certain advantages from the acoustical and the constructive point of view with regard to conventional ones. One aspect do not studied yet is the acoustic interaction between the Sonic Crystals and the ground due to, up to now, this latter is not included in the analytical models used to characterize these Sonic Crystals. We present here an analytical model, based on multiple scattering theory, to study this interaction considering the ground as a finite impedance surface. Using this model we have obtained interesting conclusions that allow to design more effectively noise screens based on Sonic Crystals. The obtained results have been compared with experimental and numerical, finding a good agreement between them.

cond-mat.mtrl-sci↗

arXiv2010

Design techniques for superposition of acoustic bandgaps using fractal geometries

Research into properties of heterogeneous artificial materials, consisting of arrangements of rigid scatterers embedded in a medium with different elastic properties, has been intense throughout last two decades. The capability to prevent the transmission of waves in predetermined bands of frequencies -called bandgaps- becomes one of the most interesting properties of these systems, and leads to the possibility of designing devices to control wave propagation. The underlying physical mechanism is destructive Bragg interference. Here we show a technique that enables the creation of a wide bandgap in these materials, based on fractal geometries. We have focused our work in the acoustic case where these materials are called Phononic/Sonic Crystals (SC) but, the technique could be applied any types of crystals and wave types in ranges of frequencies where the physics of the process is linear.

physics.flu-dyn↗

arXiv2010

Evanescent modes in Sonic Crystals: Complex relation dispersion and supercell approximation

Evanescent modes in complete sonic crystals (SC) and SC with point defects are reported both theoretically and experimentally in this paper. Plane wave expansion (PWE) and, in general, $ω(k)$ methods have been used to calculate band structures showing gaps that have been interpreted as ranges of frequencies where no real $k$ exists. In this work, we extend PWE to solve the complex $k(ω)$ problem applied to SC, introducing the supercell approximation for studying one vacancy. Explicit matrix formulation of the equations is given. This $k(ω)$ method enables the calculation of complex band structures, as well as enabling an analysis of the propagating modes related with real values of the function $k(ω)$, and the evanescent modes related with imaginary values of $k(ω)$. This paper shows theoretical results and experimental evidences of the evanescent behavior of modes inside the SC band gap. Experimental data and numerical results using the finite elements method are in very good agreement with the predictions obtained using the $k(ω)$ method.

physics.flu-dyn↗

arXiv2010

Evidences of evanescent Bloch waves in Phononic Crystals

We show both experimentally and theoretically the evanescent behaviour of modes in the Band Gap (BG) of finite Phononic Crystal (PC). Based on experimental and numerical data we obtain the imaginary part of the wave vector in good agreement with the complex band structures obtained by the Extended Plane Wave Expansion (EPWE). The calculated and measured acoustic field of a localized mode out of the point defect inside the PC presents also evanescent behaviour. The correct understanding of evanescent modes is fundamental for designing narrow filters and wave guides based on Phononic Crystals with defects.

physics.flu-dyn↗