Abstract :
[en] In this study, a linear stability analysis is performed for both monotonic and oscillatory modes within a horizontal polymersolution layer, which solely the solvent evaporates into air. The approach is based on general thermodynamic principles and alsoon the physics of the gas phase and its interactions with the liquid phase. Due to evaporation, the solvent mass fraction changesand cooling occurs at the liquid-gas interface. This can trigger solutal and thermal Rayleigh-Bénard-Marangoni instabilities in thesystem. For the monotonic mode, the effects of composition dependent diffusion coefficient and dynamic viscosity on the onsetof Rayleigh-Bénard-Marangoni convection are studied. Moreover, the effect of different total heights of the liquid-gas system onthe behavior of convection onset is considered. The results show that a variable diffusion coefficient and a variable viscosity cannotably change the onset of instability for a polyisobutylene (PIB)/toluene solution. Our model for the monotonic mode is alsosatisfactorily compared with an experimental study. For the oscillatory mode, where the relaxation time is also compositiondependent, we observe that very thin layers will be susceptible to an oscillatory instability when drying occurs in the system.Finally, an approximate model is derived exploiting the fact that the solutal Marangoni is by far the most dominant instabilitymechanism here. A negligible difference with respect to the full model confirms the predominance of the solutal Marangonimechanism.
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