Nonlinear propagation and control of acoustic waves in phononic superlattices

TL;DR

This paper explores how nonlinear and dispersive effects in phononic superlattices can be engineered to control acoustic wave propagation, enabling waveform shaping and distortion management in structured fluids.

Contribution

It introduces a novel approach to manipulate nonlinear acoustic waves in phononic superlattices by leveraging band-gap effects and dispersion for waveform control.

Findings

Nonlinear harmonics can be manipulated near band gaps.

Engineered media can achieve waveform distortion cancellation.

New propagation scenarios arise from dispersion-nonlinearity interplay.

Abstract

The propagation of intense acoustic waves in a one-dimensional phononic crystal is studied. The medium consists in a structured fluid, formed by a periodic array of fluid layers with alternating linear acoustic properties and quadratic nonlinearity coefficient. The spacing between layers is of the order of the wavelength, therefore Bragg effects such as band-gaps appear. We show that the interplay between strong dispersion and nonlinearity leads to new scenarios of wave propagation. The classical waveform distortion process typical of intense acoustic waves in homogeneous media can be strongly altered when nonlinearly generated harmonics lie inside or close to band gaps. This allows the possibility of engineer a medium in order to get a particular waveform. Examples of this include the design of media with effective (e.g. cubic) nonlinearities, or extremely linear media (where distortion can be cancelled). The presented ideas open a way towards the control of acoustic wave propagation in nonlinear regime.