Marangoni instability of self-rewetting films modulated by chemical reactions flowing down a vertical fibre

This paper examines the Marangoni instability of a self-rewetting film coating on a vertical heated fibre and its modulation by chemical reactions. A single evolution equation based on the classic thin-film model is derived to study the flow dynamics. Linear stability analysis shows that without chemical reactions, wall heating plays a stabilizing role when T_i>T₀ (T_i is the interfacial temperature and T₀ is the temperature corresponding to the minimum of surface tension in self-rewetting fluids), and it plays a destabilizing role when T_i<T₀. However, chemical reactions can strongly modulate how the wall heating affects the flow dynamics. For both situations (T_i>T₀ or T_i<T₀), the endothermic reaction further enhances respective Marangoni effects, and the exothermic reaction suppresses respective Marangoni effects. In particular, a strong exothermic reaction can totally neutralize and even reverse Marangoni effects. These findings are further confirmed by performing nonlinear traveling wave solutions and transient numerical simulations.