Biomedical subjects

S Fauve

Publications and source records attributed to S Fauve.

16 recordsLinked to original sources

PubMed2006

Transport of magnetic field by a turbulent flow of liquid sodium.

We study the effect of a turbulent flow of liquid sodium generated in the von Kármán geometry, on the localized field of a magnet placed close to the frontier of the flow. We observe that the field can be transported by the flow on distances larger than its integral length scale. In the most turbulent configurations, the mean value of the field advected at large distance vanishes. However, the rms value of the fluctuations increases linearly with the magnetic Reynolds number. The advected field is strongly intermittent.

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PubMed2005

Effect of phase noise on parametric instabilities.

We report an experimental study on the effect of an external phase noise on the parametric amplification of surface waves. We observe that both the instability growth rate and the wave amplitude above the instability onset are decreased in the presence of noise. We show that all the results can be understood with a deterministic amplitude equation for the wave in which the effect of noise is just to change the forcing term. All the data for the growth rate (respectively the wave amplitude), obtained for different forcing amplitudes and different intensities of the noise, can be collapsed on a single curve using this renormalized forcing in the presence of noise.

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PubMed2003

Scattering of sound by sound in the vicinity of the liquid-vapor critical point.

We report an experimental study of the scattering of sound by sound in the vicinity of the liquid-vapor critical point of carbon dioxide. We measure the amplitude of the scattered difference frequency wave generated by acoustic bulk nonlinearities. We observe that it is strongly increased in the vicinity of the critical point.

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PubMed2003

Nonlinear magnetic induction by helical motion in a liquid sodium turbulent flow.

We report an experimental study of the magnetic field B--> induced by a turbulent swirling flow of liquid sodium submitted to a transverse magnetic field B-->(0). We show that the induced field can behave nonlinearly as a function of the magnetic Reynolds number, R(m). At low R(m), the induced mean field along the axis of the flow, , and the one parallel to B-->(0), , first behave like R(2)(m), whereas the third component, , is linear in R(m). The sign of is determined by the flow helicity. At higher R(m), B--> strongly depends on the local geometry of the mean flow: decreases to zero in the core of the swirling flow but remains finite outside. We compare the experimental results with the computed magnetic induction due to the mean flow alone.

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PubMed2001

Noise induced bistability of parametric surface waves.

We report an experimental study on the effect of an external multiplicative noise on a subcritical bifurcation leading to the parametric amplification of surface waves. We show that the probability density function of the wave amplitude in the presence of noise has two maxima that do not correspond to any of the deterministic states. When the deterministic forcing is varied in the presence of noise, these most probable values give two new branches in the bifurcation diagram that involve a much larger difference in oscillation amplitude. The bistable region is also strongly enlarged. This noise induced bistability can be understood in the general framework of noise induced transitions.

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PubMed1999

Frozen wave induced by high frequency horizontal vibrations on a CO2 liquid-gas interface near the critical point.

We used the liquid-vapor equilibrium of CO2 near its critical point (T(C)-T=1 to 150 mK) in order to study the stability of an interface between a gas and a liquid having close densities rho(L) approximately rho(V) when submitted to high frequency f (3-57.5 Hz) horizontal vibrations (of amplitude a from 0.1 to 2.5 mm). Above a given velocity threshold (2piaf )(0) we observed a "frozen wave," corresponding to an interface profile of sinelike shape which is stationary in the reference frame of the vibrated sample cell. By varying the vibration parameters, the surface tension, and the density difference between the two phases via the temperature, it was found that the wavelength and the amplitude of the stationary profile are both increasing functions of the frequency and of the amplitude of the vibration and that they are proportional to the capillary length. Our measurements are consistent with a model of inviscid and incompressible flow averaging the effect of the vibration over a period and leading to a Kelvin-Helmholtz-like instability mechanism due to the relative motion of the two fluids.

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PubMed1993