Observation of gravity-capillary wave turbulence

We report the observation of the cross-over between gravity and capillary wave turbulence on the surface of mercury. The probability density functions of the turbulent wave height are found to be asymmetric and thus non Gaussian. The surface wave height displays power-law spectra in both regimes. In the capillary region, the exponent is in fair agreement with weak turbulence theory. In the gravity region, it depends on the forcing parameters. This can be related to the finite size of the container. In addition, the scaling of those spectra with the mean energy flux is found in disagreement with weak turbulence theory for both regimes

Fluctuations of energy flux in wave turbulence

We report that the power driving gravity and capillary wave turbulence in a statistically stationary regime displays fluctuations much stronger than its mean value. We show that its probability density function (PDF) has a most probable value close to zero and involves two asymmetric roughly exponential tails. We understand the qualitative features of the PDF using a simple Langevin type model.Comment: submitted to PR

Observation of Sommerfeld precursors on a fluid surface

We report the observation of two types of Sommerfeld precursors (or forerunners) on the surface of a layer of mercury. When the fluid depth increases, we observe a transition between these two precursor surface waves in good agreement with the predictions of asymptotic analysis. At depths thin enough compared to the capillary length, high frequency precursors propagate ahead of the ''main signal'' and their period and amplitude, measured at a fixed point, increase in time. For larger depths, low frequency ''precursors'' follow the main signal with decreasing period and amplitude. These behaviors are understood in the framework of the analysis first introduced for linear transient electromagnetic waves in a dielectric medium by Sommerfeld and Brillouin [1].Comment: to be published in Physical Review Letter

Observation of gravity-capillary wave turbulence

International audienceWe report the observation of the crossover between gravity and capillary wave turbulence on the surface of mercury. The probability density functions of the turbulent wave height are found to be asymmetric and thus non-Gaussian. The surface wave height displays power-law spectra in both regimes. In the capillary region, the exponent is in fair agreement with weak turbulence theory. In the gravity region, it depends on the forcing parameters. This can be related to the finite size of the container. In addition, the scaling of those spectra with the mean energy flux is found in disagreement with weak turbulence theory for both regimes

Scaling of ac electrical conductivity of powders under compression

International audienceWe measured, at low applied voltage, the ac electrical resistance and capacitance of a metallic powder sample under uniaxial compression. Whatever the applied stress, the frequency-dependent resistance curves can be displayed on a master curve by an appropriate rescaling. The same property is also observed for the capacitance. A one-dimensional model shows that the strong frequency dependence of the macroscopic resistance and capacitance is a consequence of the broad contact resistance distribution between grains. No microscopic model of conduction nor any parameter related to the unknown disorder need to be assumed. Relevance to other systems like random conductor-insulator mixtures or metal-cluster compounds is discussed

Recueil des contributions de la 26e Rencontre du Non-Linéaire (Paris 2023)

International audienc

Recueil des contributions de la 26e Rencontre du Non-Linéaire (Paris 2023)

International audienc