Transition to chaotic thermocapillary convection in a half zone liquid bridge

A series of fluid physics microgravity experiments with an enough long run time were performed in the "KIBO," the Japanese Experiment Module aboard the International Space Station, to examine the transition to chaos of the thermocapillary convection in a half zone liquid bridge of silicone oil with a Prandtl number of 112. The temperature difference between the coaxial disks induced the thermocapillary-driven flow, and we experimentally demonstrated that the flow fields underwent a transition from steady flow to oscillatory flow, and finally to chaotic flow with increasing temperature difference. We obtained the surface temperature time series at the middle of the liquid bridge to quantitatively evaluate the transition process of the flow fields. By Fourier analysis, we further confirmed that the flow fields changed from a periodic, to a quasi-periodic, and finally to a chaotic state. The increasing nonlinearity with the development of the flow fields was confirmed by time-series chaos analysis. The determined Lyapunov exponent and the translation error indicated that the flow fields made transition to the chaotic field with the increasing temperature difference.