Analysis of interfacial effect and boundary layer for forced convection on the macroscopic hydrophilic-hydrophobic hybrid surface: A large eddy simulation

Haotian Cong, Minli Bai, Xuecheng Lv, Yubai Li, Yongchen Song
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Abstract

Hydrophilic-hydrophobic hybrid surfaces are developed to solve the flow and heat transfer performance contradiction. However, hybrid surfaces often have micro- or nano-scale featured sizes and are used in phase change heat transfer because hydrophilic regions contribute to droplet nucleation, and hydrophobic regions contribute to bubble nucleation. In this study, large eddy simulation is used to investigate the forced convection on macroscopic hydrophilic-hydrophobic hybrid surfaces where only the surface local wettability is changed. Three hybrid surfaces with different hydrophilic-hydrophobic ratios and two homogeneous wettability surfaces are designed, and representative flow Reynolds numbers of 4000, 6000, 10 000, and 40 000 are explored to achieve different turbulent styles. The transient parameters of kinematics, vorticity, and boundary layer are analyzed to clarify the mechanism of turbulence change and eddy generation and explain the causes of variations in flow and heat transfer performances. It proves that macroscopic hydrophilic-hydrophobic hybrid surfaces are suitable for forced convection due to the drag reduction on hydrophobic regions, backflows at hydrophilic-hydrophobic interfaces, and eddies at hydrophobic-hydrophilic interfaces, which can enhance the internal disturbance and harmonize the flow and heat transfer performances. The mechanism has a profound significance in broadening the application of hydrophilic-hydrophobic hybrid surfaces and designing the arrangement of hydrophobic regions.
宏观亲水-疏水混合表面强制对流的界面效应和边界层分析:大涡模拟
开发亲水-疏水混合表面是为了解决流动和传热性能之间的矛盾。然而,混合表面通常具有微米或纳米尺度的特征尺寸,并被用于相变传热,因为亲水区域有助于液滴成核,而疏水区域有助于气泡成核。本研究采用大涡流模拟来研究宏观亲水-疏水混合表面上的强制对流,其中只改变了表面的局部润湿性。设计了三种不同亲水疏水比的混合表面和两种均匀润湿性表面,并探讨了具有代表性的 4000、6000、10000 和 40000 雷诺数流动,以实现不同的湍流风格。通过分析运动学、涡度和边界层等瞬态参数,阐明了湍流变化和涡流产生的机理,解释了流动和传热性能变化的原因。研究证明,宏观亲水疏水混合表面由于疏水区域阻力减小、亲水疏水界面产生逆流、疏水亲水界面产生漩涡,可增强内部扰动,协调流动和传热性能,因此适合强制对流。该机理对于拓宽亲水-疏水混合表面的应用范围和设计疏水区域的排列方式具有深远意义。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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