Investigation of bubble formation dynamics of gas-non-Newtonian liquid two-phase flow in a flow-focusing generator

IF 2.3 4区 工程技术 Q2 INSTRUMENTS & INSTRUMENTATION
Gang Yang, Hui-Chen Zhang
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Abstract

In the present study, we explore the dynamics of bubble formation in a flow-focusing device designed for gas-non-Newtonian liquid two-phase flow. The flow-focusing device with a cross-section of a square (300 μm × 300 μm) is constructed on polydimethylsiloxane using lithographic techniques and subsequently sealed with polymethylmethacrylate. A high-speed camera is employed to document the process of bubble formation during the experiment, complemented by computational fluid dynamics methods for an in-depth analysis. The gas is nitrogen, and the liquid is sodium carboxymethyl cellulose solutions with mass fractions of 0.1, 0.2, and 0.3%, respectively. The inlet flow rates of gas and liquid are set at 1–2 ml/min in the simulation and the experiment, and the observed flow patterns are all slug flows. Experimental findings suggest that the duration of bubble formation can be bifurcated into two distinct parts. The first part is predominantly influenced by the velocity of the inlet gas, and the correlation coefficient between velocity and time is −0.56, while the second part is impacted by the shear-thinning properties of the liquid, which are correlated with the flow index and viscosity coefficient of the non-Newtonian liquids, and the correlation coefficients are −0.47 and 0.48, respectively. The computational fluid dynamics results of gas-non-Newtonian liquid two-phase flow with gas and liquid flow rates of 2 ml/min corroborate that the manifestation of the aforementioned time segmentation phenomenon primarily depends on the vortex intensity at the bubble’s head and the orientation of pressure gradients. When the bubble neck size approaches 0, the viscosity of the surrounding liquid decreases rapidly, and alterations in the velocity field near the bubble neck trigger fluctuations in the viscosity of the non-Newtonian liquid, thereby influencing the bubble formation process.

Abstract Image

流聚焦发生器中气体-非牛顿液体两相流的气泡形成动力学研究
在本研究中,我们探讨了气泡在专为气体-非牛顿液体两相流设计的流动聚焦装置中的形成动力学。我们利用平版印刷技术在聚二甲基硅氧烷上制作了一个横截面为正方形(300 μm × 300 μm)的流动聚焦装置,随后用聚甲基丙烯酸甲酯进行了密封。在实验过程中,使用高速摄像机记录气泡的形成过程,并辅以计算流体动力学方法进行深入分析。气体为氮气,液体为羧甲基纤维素钠溶液,质量分数分别为 0.1%、0.2% 和 0.3%。在模拟和实验中,气体和液体的入口流速均设定为 1-2 ml/min,观察到的流动模式均为蛞蝓流。实验结果表明,气泡形成的持续时间可分为两个不同的部分。第一部分主要受入口气体速度的影响,速度与时间的相关系数为-0.56;第二部分受液体剪切稀化特性的影响,与非牛顿液体的流动指数和粘度系数相关,相关系数分别为-0.47 和 0.48。气体和液体流速为 2 ml/min 的气体-非牛顿液体两相流的计算流体动力学结果证实,上述时间分段现象的表现主要取决于气泡头部的涡流强度和压力梯度的方向。当气泡颈部尺寸接近 0 时,周围液体的粘度迅速降低,气泡颈部附近速度场的变化会引发非牛顿液体粘度的波动,从而影响气泡的形成过程。
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来源期刊
Microfluidics and Nanofluidics
Microfluidics and Nanofluidics 工程技术-纳米科技
CiteScore
4.80
自引率
3.60%
发文量
97
审稿时长
2 months
期刊介绍: Microfluidics and Nanofluidics is an international peer-reviewed journal that aims to publish papers in all aspects of microfluidics, nanofluidics and lab-on-a-chip science and technology. The objectives of the journal are to (1) provide an overview of the current state of the research and development in microfluidics, nanofluidics and lab-on-a-chip devices, (2) improve the fundamental understanding of microfluidic and nanofluidic phenomena, and (3) discuss applications of microfluidics, nanofluidics and lab-on-a-chip devices. Topics covered in this journal include: 1.000 Fundamental principles of micro- and nanoscale phenomena like, flow, mass transport and reactions 3.000 Theoretical models and numerical simulation with experimental and/or analytical proof 4.000 Novel measurement & characterization technologies 5.000 Devices (actuators and sensors) 6.000 New unit-operations for dedicated microfluidic platforms 7.000 Lab-on-a-Chip applications 8.000 Microfabrication technologies and materials Please note, Microfluidics and Nanofluidics does not publish manuscripts studying pure microscale heat transfer since there are many journals that cover this field of research (Journal of Heat Transfer, Journal of Heat and Mass Transfer, Journal of Heat and Fluid Flow, etc.).
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