疏水表面减阻机理及减阻效果的稳定维持方法

发布时间：2018-05-02 11:13

本文选题：疏水表面 + 减阻　；参考：《西北工业大学》2015年硕士论文

【摘要】：论文利用实验测试、数值模拟和理论分析的方法,对疏水表面的减阻机理、气膜的驻留特性及其驻留方法进行了系统研究,找到了疏水表面减阻效果的稳定维持方法。所开展的主要研究内容及创新性成果包括:(1)在重力式低速水洞中,利用热线测速仪对多种疏水表面的湍流边界层流场进行了实验研究。近壁区的平均速度剖面会抬升,湍流度降低,证实了滑移的存在;基于小波分析理论,提出了湍流相干结构的精确提取方法,并发现壁面的疏水性对涡结构强度有抑制作用。(2)发现了疏水表面上气膜驻留的两种模式:气层模式和气泡模式。建立了相应的减阻模型,总结了气层和气泡消失的不同过程,揭示了疏水表面减阻不稳定的机理。(3)对格子Boltzmann方法进行了改进,并利用该方法对疏水表面的润湿性进行了表征。建立了与气层模式和气泡模式对应的格子Boltzmann模型,得到了流速、固液作用强度和微结构对疏水表面气膜驻留特性和减阻特性的影响规律。(4)基于空化效应,提出了在微结构上实现空化进而驻留气膜的方法。通过理论分析,得到了微结构的设计准则,并根据该准则,利用数值模拟,验证了微结构上实现空化的可能性,并分析了流速、微结构和接触模式对微结构空化的影响规律。(5)研究了基于人工通气的气膜驻留方法,对该情况下的气膜边界层进行了测试和分析,得到了气膜对平均速度剖面、边界层厚度、滑移特性、减阻特性和涡结构特性的影响规律,证实了该方法可以维持气膜的存在和疏水表面的减阻效果。
[Abstract]:By means of experimental test, numerical simulation and theoretical analysis, the mechanism of drag reduction on hydrophobic surface, the residence characteristics of gas film and its resident method are systematically studied in this paper, and the stable maintenance method of drag reduction effect on hydrophobic surface is found. The main research contents and innovative results include: (1) the turbulent boundary laminar flow field on various hydrophobic surfaces has been experimentally studied in a gravity low-speed tunnel with a hot-wire velocimeter. The average velocity profile near the wall will rise and the turbulence degree will decrease, which proves the existence of slippage. Based on the wavelet analysis theory, an accurate method for extracting turbulent coherent structures is proposed. It is also found that the hydrophobicity of the wall has an inhibitory effect on the strength of the vortex structure. (2) two modes of gas film residence on the hydrophobic surface are found: the gas layer model and the bubble mode. The corresponding drag reduction model was established, the different processes of gas layer and bubble disappearance were summarized, and the mechanism of drag reduction instability on hydrophobic surface was revealed. The lattice Boltzmann method was improved, and the wettability of hydrophobic surface was characterized by this method. The lattice Boltzmann model corresponding to the gas layer model and the bubble model is established. The effects of flow rate, solid-liquid interaction intensity and microstructure on the residence characteristics and drag reduction characteristics of the gas film on the hydrophobic surface are obtained based on the cavitation effect. A method to realize cavitation on the microstructure and then stay the gas film is presented. Through theoretical analysis, the design criteria of microstructures are obtained. According to these criteria, the possibility of cavitation in microstructures is verified by numerical simulation, and the velocity of flow is analyzed. The effect of microstructures and contact modes on the cavitation of microstructures. (5) the method of gas film residence based on artificial ventilation was studied. The film boundary layer was tested and analyzed, and the average velocity profile and boundary layer thickness were obtained. It is proved that the method can maintain the existence of gas film and the drag reduction effect of hydrophobic surface.
【学位授予单位】：西北工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U661.311

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