考虑非稳态自然对流的固体溶解过程数值模拟

Numerical simulation of solid dissolution process considering unsteady natural convection

为了揭示封闭腔内考虑非稳态自然对流的固体溶解的流动、传质以及固体表面形貌变化规律,利用溶解动力学和传质学相关理论,建立了固体溶解过程的二维数学模型,并借助有限元分析软件COMSOL进行了数值模拟,得到了溶解过程中固体尺寸对流动、传质和固体表面形貌的影响规律.研究结果表明:该方法可以很好地捕捉由于溶解引起的界面运动和变形的位置,进而获得速度分布及浓度分布的演化过程.在Ra=1×107,当ε≤0.4,流场中有2个对称且方向相反的漩涡,浓度分布呈中心对称;随着ε增大,溶液与壁面之间的作用增强,流场中2个对称且方向相反漩涡转变为统一的单漩涡,且传质效率降低;固体表面形貌的演化与固体尺寸和时间有关.

To reveal the variation patterns of flow structure,mass transfer and solid surface morphology in solid dissolution process under the effect of unsteady natural convection inside closed cavity,a two-dimensional mathematical model of solid dissolution process was established based on theories of dissolution kinetics and mass transfer.The finite element software COMSOL was used for numerical stimulation to investigate the effect of solid size on the flow,mass transfer and solid surface morphology.The results show that the method can well capture the interface motion and position caused by dissolution,and obtain the propagations of flow and mass transfer.At Ra=1×107,while ε≤0.4,two counter-rotating cells are formed in the cavity and iso-concentrations are symmetrical about the centre line;with the increase of ε,two counter-rotating cells become a primary cell in the cavity due to the increasing effect of wall confinement.As a result,the mass transfer is also decreased.The solid surface morphology depends not only on the solid size but also on the time.