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蒸发弯月面附近的传热传质过程具有非常广阔的应用背景而得到人们的广泛关注。但另一方面，由于相变现象及微尺度现象的存在，又使得该过程的研究具备相当的复杂性。近年来，Gazzola等人在边界条件对称的情况下，观测到在竖直管中，蒸发的凸弯月面下存在有非对称流动。而根据以往人们针对蒸发液面的研究，对称的边界条件下产生的流动往往应该是对称的。为了深入探究该现象的产生及原因，本文建立了一套数理模型以描述该蒸发弯月面附近的传热传质过程。本模型包括了界面上的蒸发，蒸汽在空气中的扩散，液体的Marangoni流动以及自然对流等过程。模拟结果与实验结果吻合。特定条件下对称流动的不稳定性被认为是这种非对称流动产生的原因。“,”Evaporating menisci have gained increasing attentions because of their wide applications. Recently, Gazzola, et al. have observed asymmetrical Marangoni flow patterns under a convex meniscus though the boundary conditions were symmetrical. The experimental results are distinct from those in previous literatures. In this paper, a numerical model is proposed to clarify the mechanism behind the abnormality. Factors including liquid evaporation at the interface, vapor transport in the gas domain, Marangoni effect and the natural convections are considered. The simulation well reproduced the experiments and further indicated that the symmetrical Marangoni convections under certain conditions are instable. Once a perturbation is performed, the original symmetrical convection will evolve to be a single vortex convection.