微通道内不混溶气液两相二氧化碳界面动力学行为的格子Boltzmann研究

将高精度的二氧化碳状态方程与气液两相流格子Boltzmann方法中的伪势模型耦合，研究微通道内二氧化碳气液两相流动的界面动力学行为，包括二氧化碳气泡和液滴的分裂、合并、变形，以及气液两相二氧化碳在演化过程中的质量交换.研究发现：当分裂和合并行为达到平衡，并且两相之间不发生质量交换时流动达到稳态.稳态时的流型主要依赖于表面张力，惯性力，管道的润湿性，以及初始体积分数.当表面张力较大时，微通道内形成的二氧化碳气泡或液滴会收缩成圆形，此时二氧化碳气泡或液滴会堵塞微通道，形成段塞流；随着表面张力的减小，形成的气泡或液滴不容易收缩，在微通道内更容易发生变形，出现泡状流或环状流.当壁面润湿性为强疏水性时，二氧化碳在微通道中的流动为环状流，其它润湿性下，流型为段塞流.体积分数较小时，二氧化碳两相流动的流型为段塞流，体积分数较大时，流型为环状流.

Interfacial Dynamics of Immiscible Gas-Liquid Two-phase Flow for CO2 in Microchannel: Lattice Boltzmann Method

An accurate equation of state (EOS) for carbon dioxide is coupled into an improved lattice Boltzmann equation (LBE) model. With the model continuous interfacial dynamics of carbon dioxide in two phase in a microchannel, including breaking up, coalescence, deformation, and mass exchange between gas and liquid phases, is studied. It is found that flows achieve a steady-state as balance of breaking up and coalescence is reached, and mass exchange occurs. Comprehensive results show that flow shape at steady-state depends mainly on surface tension, inertial force, wettability of channel surface, and initial volume fraction. Specially, formative bubbles or droplets are almost spherical as inertial force is smaller than surface tension. As surface tension overcomes inertial force, slug flow is formed since bubbles or droplets are easy to expand to contact with solid surface. On the other hand, it shows that influence of wettability on flow pattern is also important. Slug flow is observed if contact angle is small while annular flow is observed if contact angel is large. At different volume fraction slug flow and annular flow are obtained.