液桥重开过程的两相格子Boltzmann模型及计算

发布时间：2018-03-09 04:00

本文选题：格子Boltzmann方法　切入点：两相流动　出处：《西安交通大学学报》2016年09期 　论文类型：期刊论文

【摘要】：根据最近提出并发展的相场格子Boltzmann方法,建立了阻塞气道重开过程的不混溶两相流动模型和计算方法。基于自由能理论、引入指示函数对两相流体界面进行描述,指示函数的演化遵循Cahn-Hilliard方程,具有坚实的物理基础;通过压力分布函数对流场信息进行求解,可有效降低密度梯度离散所诱发的数值不稳定性;引入势能形式的界面张力项,与压力形式的相比可有效抑制界面处的假拟速度。应用该模型对液桥重开的两相流动过程进行了数值研究,并着重分析了毛细数对阻塞液桥演化过程的影响,结果表明,阻塞液桥的轴向厚度变化存在临界毛细数现象,当毛细数大于临界值时,阻塞液桥的轴向厚度随时间逐渐减小,最终发生破裂,实现气道的重开;利用该模型重现了无液滴和有液滴形成的两种气道重开现象,对比研究发现,在无液滴形成的气道重开过程中,壁面经历的压力变化更大。研究工作可为深入认识人体肺气道的生理病理机制、微通道内不混溶两相流体的流动规律提供一定的理论依据。
[Abstract]:Based on the recently proposed and developed phase field lattice Boltzmann method, an immiscible two-phase flow model and a computational method for re-opening of blocked airways are established. Based on the theory of free energy, an indicator function is introduced to describe the interface of the two-phase fluid. The evolution of the indicator function follows the Cahn-Hilliard equation and has a solid physical foundation; the numerical instability induced by density gradient discretization can be effectively reduced by solving the flow field information of the pressure distribution function; the interfacial tension term in the form of potential energy is introduced. Compared with the pressure form, the pseudo-pseudo velocity at the interface can be suppressed effectively. The numerical study on the two-phase flow process of the reopening of the liquid bridge is carried out by using the model, and the effect of the capillary number on the evolution process of the blocked liquid bridge is emphatically analyzed. The results show that, When the capillary number is greater than the critical value, the axial thickness of the clogged liquid bridge decreases gradually with time, and finally breaks down, realizing the re-opening of the airway. The model was used to reproduce the re-opening of two kinds of airways without droplets and droplets. The results of comparative study showed that in the course of re-opening of airways without droplets, The study can provide a theoretical basis for further understanding the physiological and pathological mechanism of human pulmonary duct and the flow law of immiscible two-phase fluid in microchannels.
【作者单位】：西安交通大学能源与动力工程学院;
【基金】：国家自然科学基金资助项目(51176146,51506168) 中组部“千人计划”青年人才项目西安交通大学青年拔尖人才支持计划
【分类号】：TK124

【参考文献】