T型微通道内液滴在幂律流体中运动机理的格子Boltzmann方法研究

Study of Movement Mechanisms of Droplets in Power-Law Fluids in T-Junction Microchannels With the Lattice Boltzmann Method

采用非Newton不可压两相流格子Boltzmann模型研究了T型微通道内Newton液滴在非Newton幂律流体中的运动过程.研究了非Newton流体幂律指数n、主管道毛细数Ca、两相流量比Q、两相黏度比M以及主管道壁面润湿性θ对液滴在T型微通道内的形成尺寸、形成时间和变形参数(DI)的影响.研究结果表明:首先,主管道流体幂律指数n从0.4增加到1.6时,液滴的形成尺寸近似呈线性减小,而液滴的形成时间和变形参数先快速减小,然后缓慢减小;其次,黏度比对液滴形成尺寸、液滴形成以及变形参数的影响与幂律指数的影响基本一致;再者,随着Ca和主管道壁面润湿性的增加,形成液滴的尺寸近似呈线性减小,形成液滴的时间和变形参数先快速减小然后缓慢减小,且减小趋势随幂律指数的增加而减缓;最后,研究结果还表明主管道和子管道的流量比Q越大,液滴形成时间越长,液滴形成尺寸和变形参数越小.

The movement mechanisms of Newtonian droplets in power-law fluids in T-junction microchannels were studied with the lattice Boltzmann method.The effects of power-law index n,capillary number Ca,flow ratio Q,viscosity ratio M,and surface wettabilityθon the droplet formation size,the formation time and the deformation index(DI)were investigated in detail.The results show that,first,with the increase of power-law index n from 0.4 to 1.6,the droplet formation size decreases almost linearly,and both the droplet formation time and the deformation index decrease quickly at first and then much more slowly.Second,the influences of the viscosity ratio on the droplet formation size,the formation time and the deformation index are basically the same as those of the power law index.In addition,with the increases of Ca andθof the main channel,the droplet formation size decreases almost linearly,while the droplet formation time and deformation index decrease rapidly at first and then slowly,and the decreasing rates weaken with the increase of the power-law index.At last,with the increase of flow ratio Q of the continuous phase over the dispersed phase,the droplet formation size increases,and the droplet formation time as well as the deformation index decrease.