Effects of thermocapillarity on the dynamics of an exterior coating flow of a self-rewetting fluid

摘要

The effects of thermocapillarity on the dynamics of an exterior coating flow of a self-rewetting fluid on a vertical fibre are investigated theoretically. Whereas surface tension decreases linearly with temperature for most fluids, the surface tension of a self-rewetting fluid exhibits a well-defined minimum. We developed an evolution equation for the interface in the framework of the long wave approximation. Linear stability analysis and numerical simulations on the nonlinear evolution have been performed to investigate the effects of thermocapillarity for axisymmetric disturbances. The results showed that thermocapillarity plays different roles in the stability and dynamics depending on the value of difference between the temperature at the interface, (Theta) over bar (i), and the temperature corresponding the minimum of the surface tension, Theta(0). The results of linear stability analysis showed that the thermocapillarity is destabilizing or stabilizing as (Theta) over bar (i) - (Theta) over bar (0) is negative or positive. At the nonlinear stage, for (Theta) over bar (i) - (Theta) over bar (0) 0 more pronounced beads-like structures are observed due to the reinforcement between the thermocapillarity and the Rayleigh-Plateau instability. However, for (Theta)over bar(i) - (Theta) over bar (0) 0 the thermocapillarity weakens the tendency of formation of beads due to the Rayleigh-Plateau mechanism. (C) 2019 Elsevier Ltd. All rights reserved.