Dependency of transition in thermocapillary convection on volume ratio in annular pools of large-Pr fluid in microgravity

Abstract

Thermocapillary convection driven by the horizontal temperature gradient is a typical nonlinear dynamical system. As the applied temperature difference increases, the flow undergoes a series of transitions into turbulence. Volume ratio of the liquid layer Vr (liquid volume/volume of the container) is a critical parameter that affects transition behaviors of the convection. Direct numerical simulations on thermocapillary convection in annular liquid pools with various volume ratios are carried out. Characteristics of the oscillatory convection are detected by time series and frequency spectrum analyses. The dynamic mode decomposition (DMD) method is also adopted to investigate inherent structures of the flow field. Effect of Vr on oscillation characteristics under a wide range of temperature differences from 10K to 90K is discussed. Results show that in annular pools with lager volume ratios, the thermocapillary convection is chaotic under very large ΔT and its transition behaviors are more complicated.