Directional asymmetry of the nonlinear wave phenomena in a 3-dimensional phononic granular crystal under gravityReport as inadecuate




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* Corresponding author 1 LAUM - Laboratoire d-acoustique de l-université du Maine

Abstract : A periodic ordered structure of monodisperse spherical beads forms a granular phononic crystal. The granular crystals combine in their dynamic behavior the effects of the geometrical periodicity phononic effects, the rotational degrees of freedom rotational inertia and nonlinearities. We report the experimental observation of the asymmetry introduced by the gravity in the nonlinear transformation of acoustic waves in granular assemblages. Because of the gravity, the contact pre­-compression increases with depth inducing variations with depth of not only the linear and nonlinear elastic moduli but also of the linear and nonlinear dissipation of the acoustic waves. We show experimentally and explain theoretically that the amplitude of the self­demodulated wave i.e., the amplitude of the wave emitted by a parametric antenna through a frequency­mixing down­ conversion process depends in the granular media on whether the propagation of the pump waves is in the direction of the gravity or in the opposite direction. The measurements of the gravity­induced asymmetry in the nonlinear acoustic phenomena allow to compare the in­depth distributions of the contact nonlinearity and of acoustic absorption. This work is supported by project -STABINGRAM- ANR­2010­BLAN­0927­03.

Keywords : Granular phononic crystal Nonlinear Asymmetry





Author: Aurelien Merkel - Vincent Tournat - Vitaly Gusev

Source: https://hal.archives-ouvertes.fr/



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