Abstract:

To improve the efficiency of capillary evaporation process in seawater desalination, an appropriate capillary pressure should be maintained for the porous media with a fast bubble passing process. A parametric model of the porous media structure was established to investigate the dynamic characteristics of the bubbles passing through the channel of porous media. The purpose was to find general rules that could make it easier for bubbles to pass through the porous medium layer by regulating the size and channel arrangement of the porous structure under a steady capillary pressure. The lattice Boltzmann pseudo-potential model was used to analyze the influencing factors, such as materials’porosity, skeleton’s wettability, channel arrangement, bubbles’ initial velocity in the horizontal direction, etc. The dependable variables including the transportation characteristics of bubble morphology, rising velocity and capillary pressure in the bubble rising process were discussed. This study obtained an operable porosity range and the criterion for the selection of wettability and channel arrangement of the porous structure. Furthermore, it revealed that bubbles with a certain horizontal velocity could detach from the porous media faster than those without horizontal velocity in the actual evaporation process.

Key words: lattice Boltzmann method, porous media, bubble dynamics

摘要：

为提高毛细蒸发海水淡化技术中的蒸发效率，多孔介质层需要维持一定的毛细压力，同时还要确保气泡能够快速通过。基于此背景，本文建立了多孔介质参数化模型，探究了气泡穿越多孔介质间隙过程的运动特征，研究在保持一定孔隙毛细压力的同时，通过调控孔道尺寸及排布从而使气泡能够更快速地通过多孔介质层。基于格子Boltzmann伪势模型分析了多孔介质孔隙率、壁面润湿特性、孔道排布及气泡水平方向初速度等对气泡形貌、上升速度、与壁面平均接触面积及孔隙毛细力的影响，获得了多孔介质的孔隙率设计范围，骨架润湿特性调控以及孔道排布方式的选择依据。同时还获得了在实际蒸发过程中，可以使气泡存在一定的水平方向初速度，从而能够更快地脱离多孔介质的策略。

关键词: 格子Boltzmann方法, 多孔介质, 气泡动力学