Numerical study of low frequency g-gitter effect on thermal diffusion

Abstract

Convection has a major impact on diffusion in fluid mixtures either on the Earth or in the microgravity condition. G-jitters, as the primary source that induces the vibrational convection in space laboratories, should be studied thoroughly in order to improve the diffusion-dominated fluid science experiments. In this paper we consider the effect of g-jitters on thermal diffusion. The mixture water-isopropanol (90:10 wt%) bounded in a cubic cell is simulated with a lateral heating and various vibration conditions. The fluid flow, concentration and temperature distributions are thoroughly analyzed for different g-jitter scenarios. It is shown that the overall effect of vibrations on diffusion can be regarded basically as a nonlinear interaction between the effects caused by each individual g-jitter component. In the presence of large static residual gravity, the effect of convection on diffusion is very significant, thus resulting in a limited Soret separation. On the contrary, the importance of periodic vibration on diffusion changes according to the frequency. Low frequency vibrations exhibit a more dangerous effect on diffusion measurements with respect to high frequency vibrations. The dependence of the Soret separation on frequency and the driving mechanisms at low frequency g-jitters are discussed on the basis of these behaviors. keyword: Thermal diffusion, Convection, Numerical simulation, Finite volume, Microgravity, G-jitter