Catégorie : Article

L. Bellon, L. Fourtune, V. Ter Minassian and M. Rabaud, Physical Review E 58 565-574 (1998)

doi: 10.1103/PhysRevE.58.565

We present a mechanism of limitation for the possible wave numbers above an instability threshold. This mechanism is experimentally investigated in the interfacial instability of directional viscous fingering in a finite system. It is shown experimentally to be controlled by the divergence of a phase-diffusion constant. Theoretically, this limitation on the low value of the accessible wave numbers is a consequence of the interaction between the fundamental and the first harmonic modes. The analysis of coupled amplitude equations demonstrates theoretically the existence of a divergence of a phase-diffusion constant when approaching the threshold of a parity-breaking instability.

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A. Garcimartin, A. Guarino, L. Bellon and S. Ciliberto, Physical Review Letters 79 3202-3205 (1997)

doi: 10.1103/PhysRevLett.79.3202

We present the data of a mode-I fracture experiment. The samples are broken under imposed pressure. The acoustic emission of microfractures before the breakup of the sample is registered. From the acoustic signals, the position of microfractures and the energy released are calculated. A measure of the clustering of microfractures yields information about the critical load. The statistics from energy measurements strongly suggest that the fracture can be viewed as a critical phenomenon; energy events are distributed in magnitude as a power law, and a critical exponent is found for the energy near fracture.

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