T型受限微通道内液滴生成特性数值模拟

Numerical simulation of droplet generation characteristics in T-confined microchannel

为给控制液滴均匀高频的生成提供参考,针对受限微通道内液滴的生成,考虑流体物性和流动条件的影响,进行了T型受限微通道内液滴生成特性的数值模拟研究。利用COMSOL软件建立了液滴生成过程仿真模型,采用相场法探究了毛细数、两相流量比、黏度比以及壁面润湿性对液滴生成的影响。研究结果表明:当连续相黏度为0.01 Pa·s,分散相速度和黏度分别为0.005 m/s和0.001 Pa·s,连续相毛细数从0.001 5增大到0.007 5时,无量纲液滴长度从2.8幂指数减小到1.5,无量纲液柱长度从2.6线性增大到7.6,液滴生成频率从每秒30个幂指数增大到52个;当连续相黏度为0.01 Pa·s,分散相黏度为0.001 Pa·s,流量比从0.1增大到0.9时,无量纲液滴长度从1.05线性增大到2.55,无量纲液柱长度从6.49幂指数减小到2.51,液滴生成频率从每秒170个幂指数减小到65个;当连续相速度为0.01 m/s,分散相速度为0.005 m/s,黏度比从0.025增大到0.5时,无量纲液滴长度从1.72函数式增大到2.1,无量纲液柱长度从3.11函数式增大到3.9,液滴生成频率从每秒31个函数式减小到24个;壁面润湿性会影响液滴的形态,但并无明显的函数关系;流体物性和流动条件对液滴的生成具有显著影响。

To provide reference for controlling the generation of uniform high frequency of drop-lets,aimed at droplet generation in confined microchannels,considering the influence of fluid physical properties and flow conditions,numerical simulation of droplet formation in a T-confined microchannel was carried out.Using COMSOL software,droplet generation process simulation model was established,and the phase field method was adopted to explore the capillary number,two-phase flow ratio,viscosity ratio and wall wettability effects on droplet generation.Results showed that when the continuous phase viscosity is 0.01 Pa·s,and the dispersed phase velocity and viscosity are 0.005 m/s and 0.001 Pa·s,respectively,as the continuous phase capillary number increases from 0.0015 to 0.0075,the continuous phase capillary number increased from 0.0015 to 0.0075,the dimensionless droplet length decreased from 2.8 power index to 1.5,the dimensionless liquid column length increased linearly from 2.6 to 7.6,the droplet generation fre-quency increased from 30 power exponents per second to 52;when the continuous phase viscosity is 0.01 Pa·s,the dispersed phase viscosity is 0.001 Pa·s,and the flow ratio increased from 0.1 to 0.9,the dimensionless droplet length increased linearly from 1.05 to 2.55,the dimension-less liquid column length decreased from 6.49 power index to 2.51,the droplet generation fre-quency decreased from 170 power index per second to 65,when the continuous phase velocity is 0.01 m/s,the dispersed phase velocity is 0.005 m/s,and the viscosity ratio increased from 0.025 to 0.5,and the dimensionless droplet length increased from 1.72 to 2.1 The length of the dimen-sionless liquid column increased from 3.11 to 3.9,and the droplet generation frequency decreased from 31 functions per second to 24.Wall wettability affects the morphology of droplets,but there is no obvious functional relationship.The physical properties and flow conditions of fluid have significant influence on droplet formation.