Local probe in a Rayleigh-Benard experiment in liquid helium

Local probe in a Rayleigh-Benard experiment in liquid helium

2014 We have measured, in a Rayleigh-Benard experiment in liquid helium, the time dependent effects occurring above the onset of convection, using a local probe. Results are very dependent on the aspect ratio 0393, ratio of the cylinder cell radius to its height. For a small aspect ratio, 0393 = 2 and 0393 = 2.5, well defined sharp oscillations are present for a large range of Rayleigh numbers....

A Cosmological Experiment in Liquid Helium

ALTHOUGH the birth of the universe is inaccessible to human experimental investigation, aspects of cosmological theories can nonetheless be explored in the laboratory. Tiny inhomogeneities in the mix of particles and radiation produced in the Big Bang grew into the clusters of galaxies that we see today, but how those inhomogeneities arose and grew is still unclear. Cosmologies based on grand u...

Rayleigh-Bénard experiment in liquid helium ; frequency locking and the onset of turbulence

2014 In a Rayleigh-Bénard experiment in liquid helium, we study the time-dependent regimes, above the onset of convection, in a parallelepipedic cell with two convective rolls of oblate cross-section 03B1 = 1.90, where 03B1 is the rolls wave number. A first frequency f1, associated to oscillating rolls, appears for a Rayleigh number R ~ 2 x 104, then for R ~ 2.7 104 a second frequency f2, much ...

Heat transport in turbulent rayleigh-Benard convection

We present measurements of the Nusselt number N as a function of the Rayleigh number R in cylindrical cells with aspect ratios 0. 5</=gamma identical withD/d</=12.8 ( D is the diameter and d is the height). We used acetone with a Prandtl number sigma = 4.0 for 10(5) less, similarR less, similar4x10(10). A fit of a power law N = N(0)R(gamma(eff)) over limited ranges of R yielded values of gamma(...

Surface deflection in Rayleigh-Benard convection