化工学报 ›› 2020, Vol. 71 ›› Issue (4): 1510-1519.doi: 10.11949/0438-1157.20191331

• 流体力学与传递现象 • 上一篇    下一篇

流动聚焦微通道内牛顿微液滴在幂律剪切致稀流体中的生成研究

陈琦1(),李京坤1,宋昱2,何倩1,李雪芳1()   

  1. 1. 山东大学热科学与工程研究中心,山东 济南 250061
    2. 清华大学能源与动力工程系,北京 100084
  • 收稿日期:2019-11-04 修回日期:2020-01-09 出版日期:2020-04-05 发布日期:2020-02-10
  • 通讯作者: 李雪芳 E-mail:cq019@outlook.com;lixf@email.sdu.edu.cn
  • 作者简介:陈琦(1995—),男,硕士研究生,cq019@outlook.com
  • 基金资助:
    山东省自然科学基金项目(ZR2017BEE003);山东大学基本科研业务费项目

Newtonian droplet generation in shear-thinning fluids in flow-focusing microchannel

Qi CHEN1(),Jingkun LI1,Yu SONG2,Qian HE1,Christopher David M2,Xuefang LI1()   

  1. 1.Institute of Thermal Science and Technology, Shandong University, Jinan 250061, Shandong, China
    2.Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
  • Received:2019-11-04 Revised:2020-01-09 Online:2020-04-05 Published:2020-02-10
  • Contact: Xuefang LI E-mail:cq019@outlook.com;lixf@email.sdu.edu.cn

摘要:

采用开源CFD软件OpenFOAM中的interFoam求解器对流动聚焦微通道内微液滴的形成过程进行了数值模拟。通过与文献中的实验数据进行对比,验证了VOF模型和幂律非牛顿流体模型的准确性。并以此为基础模拟了幂律剪切致稀流体中牛顿微液滴的形成过程,研究了幂律流体的幂律指数n和稠度系数K对微液滴生成的影响。研究表明,在滴状和挤压状流型中,离散线颈部宽度与周期内剩余时间呈幂律关系;离散线长度在坍塌阶段呈现线性缓慢增长,在夹断阶段呈现近似指数迅速增长的趋势。随着nK的增大,液滴的尺寸逐渐减小,而生成频率则逐渐增大,且n的变化比K的变化对其产生的影响更明显。

关键词: 多相流, 流动聚焦微通道, 微流体学, 非牛顿流体

Abstract:

The interFoam solver in the open source CFD software OpenFOAM was used to numerically simulate the formation of micro-droplets in a flow-focused microchannel. Predictions using the volume-of-fluid(VOF) model and the power-law non-Newtonian model were first validated against measurements in the literature. Then, the formation of Newtonian droplets in power-law shear-thinning fluids was modeled in three different flow regimes. The results illustrate the effects of the power-law index(n) and the consistency coefficient(K) of the power-law fluid on the droplet generation. The results show that the minimum width of the stretching thread has a power-law relationship with using the remaining time in the droplet release cycles in the squeezing and dripping regimes. The thread length increases slowly during the collapse stage and then grows rapidly during the pinch-off stage. The final droplet length decreases with increasing n or K. However, the generation frequency increases as n or K increase. The results also show that n has a greater effect than K on the droplet formation.

Key words: multiphase flow, flow-focusing microchannel, microfluidics, non-Newtonian fluids

中图分类号: 

  • O 359+.2

表 1

方程各项离散格式"

表达式离散格式
ddt?(ρu)?t,?α?tCrankNicolson 1

div

??(ρuu),??(αu)Gauss linear Upwind grad(U)
??(α(1-α)uc)Gauss Interface Compression
grad?u,?αGauss linear
snGrad?pcorrected
Laplacian??(μ(?u+?uT))Gauss linear corrected
interpolation(X)flinear

图1

流动聚焦型微通道几何模型"

图2

网格独立性验证"

表2

两相流体属性设置"

流体密度/(kg/m3)K/(Pa·sn)n界面张力/(mN/m)
离散相9200.011129.1
连续相10000.2~0.70.3~1

图3

液滴脱离过程中形态变化对比"

图4

液滴生成过程中主要形态参数的瞬态变化"

图5

微通道内速度及黏度分布状况"

图6

液滴形成过程中速度分布(Qd = 60 μl/min,Qc = 480 μl/min,K = 0.35 Pa?sn,n = 0.47)"

图7

不同n下不混溶线形态的变化过程(Qd = 60 μl/min,Qc = 480 μl/min,K = 0.35 Pa?sn)"

图8

不同n幂律流体中牛顿液滴的形成机制(Qd = 60 μl/min,Qc = 480 μl/min,K = 0.35 Pa?sn)"

图9

液滴尺寸及生成频率随n的变化(Qd = 60 μl/min,Qc = 480 μl/min,K = 0.35 Pa?sn)"

图10

不同K下不混溶线形态的变化过程(Qd = 60 μl/min,Qc = 480 μl/min,n = 0.47)"

图11

不同K幂律流体中牛顿液滴的形成机制(Qd = 60 μl/min,Qc = 480 μl/min,n = 0.47)"

图12

液滴长度及生成频率随K的变化(Qd = 60 μl/min,Qc = 480 μl/min,n = 0.47)"

图13

液滴长度与连续相毛细数的关系"

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