Effect of Density Fluctuation on Flow in Rotational Near-Critical Fluid

摘要

We investigated on phenomena in a shear flow caused by rotational Couette flow in a near-critical fluid. The aim of the present study is to clarify the effect of density fluctuation on the flow near the critical point. To investigate the effect of density fluctuation on shear flow, we conducted velocity measurements and light scattering experiments to measure correlation length in fixed shear rates. The experiments were conducted under microgravity conditions using drop tower (MGLAB) as well as under terrestrial conditions. We found that as the temperature approaches the critical point, the velocity profile becomes very different from usual Couette flow pattern for a radial direction. The results suggest that an increase in the fluctuation near the critical point has a great influence on the flow. In static field, the measured correlation lengths are qualitatively consistent with the theoretical values. We also found, however, that in shear flow field the correlation length becomes much longer than that in static field. The result is in accord with the order estimation that we made using characteristic wave number and the lifetime of the fluctuations.