【作者】 汪洋；

【导师】 周治平；

【作者基本信息】 哈尔滨工业大学 ， 微电子学与固体电子学， 2016， 博士

【摘要】 减少微流体器件及水面舰艇与流体的摩擦阻力,对于提高器件性能及舰艇速度具有重要意义。为此,减少固-液界面摩擦阻力成为研究热点,国内外研究学者就减阻问题开展了大量理论研究。然而,对于微纳结构固-液界面减阻效应的研究还不够深入,其内在机理尚未完全弄清并且缺乏实验验证。本文建立了微观结构固-液界面空泡减阻模型,理论研究了表面微结构对减阻的影响,提出固-液界面微弱摩擦阻力测试方法,应用这种方法对制备的超疏水和超疏油表面与液体的摩擦阻力进行测量,实验研究了表面微纳结构对减阻的影响。超疏水表面存在气泡,从而减少了固-液接触面积,而气泡角度和微观结构的变化影响固-液界面减阻效应。本文建立了微观结构固-液界面空泡减阻模型,分析了表面空泡角度和微观结构对减阻的影响。理论分析表明:空泡角度影响流体边界滑移长度及固-液界面摩擦阻力,空泡角度为0°时,流体边界滑移长度最大,固-液界面摩擦阻力最小;表面微纳结构影响减阻特性,减少微结构固-液接触面积,可以提高超疏水表面减阻效果。依据理论分析结果,采用一步浸泡法和化学沉积法在金属基底上制备出具有不同微纳结构的超疏水表面。实验结果表明具有锥形结构的超疏水表面减阻效果最佳,在流速为1.5 m/s时,减阻率约为32%,同时具有锥形结构的超疏水表面具有更好的耐久性,经过52小时冲刷试验后,表面仍保持稳定的减阻效果。目前测量固-液界面摩擦阻力的方法主要采用间接测量法,主要通过研究流体边界滑移长度间接分析固-液界面减阻效应。本文提出固-液界面微弱摩擦阻力直接测量方法。根据测量方法采用力传感器搭建了固-液界面摩擦阻力测试装置,为减阻研究提供了实验平台。基于提出的固-液界面摩擦阻力测试方法,测量制备的超疏水表面与水的摩擦阻力,通过实验验证微观结构固-液界面空泡减阻模型的正确性。超疏油表面的制备仍是难点,这也限制了超疏油表面减阻的研究。本文提出并实现了采用电沉积法与氧化法相结合的复合方法制备铜基超疏油表面,分析了微纳结构对表面疏油性及减阻的影响。研究发现与普通微纳结构相比,悬垂形结构可以提高表面疏油性及减阻效果。制备的具有悬垂形结构的超疏油表面与油滴接触角约为156°,滚动角约为7°,在流速为1.5 m/s时,减阻率约为23%,经过52小时冲刷试验后,表面仍具有较好的减阻效果。在此基础上,利用复合方法在转子上制备出超疏油表面并通过液浮支撑式转子样机进行测试,结果表明,超疏油表面可以有效减少转子与油的摩擦阻力,提高转子的转速。更多还原

【Abstract】 Reduce the frictional resistance between microfluidic devices and surface vessels and the fluid,which has important significance to improve the device performance and ship speed.Hence,reducing solid-liquid interfacial friction has been the research hotspots.The domestic and foreign scholars have lots of theoretical research on drag reduction problem.However,the study of drag reduction effect of solid-liquid interface with micro/nano structure is not profound enough and the internal mechanism is not clarified.It also lacks of experimental verification.The paper builds up a model of cavitation drag reduction on solid-liquid interface with microstructure and study the influence of surface microstructure to the reduction of frictional resistance theoretically.We suggest the test method for weak frictional resistance of solid-liquid interface and applie this method to measure frictional resistance on the prepared superhydrophobic and superoleophobic surfaces.We also study the influence of surface microstructure to the reduction of frictional resistance by experiment.There are many bubbles on superhydrophobic surface.The bubbles can reuduce contact area between solid and liquid.While the change of bubble angle and microstructure affects the drag reduction effect of solid-liquid interface.The paper builds up a model of cavitation drag reduction at solid-liquid interface with micro structures.We analyze the influence of surface cavitation and microstructure on drag reduction.The theoretical analysis shows that the bubble angle affects the fluid boundary slip length and solid-liquid interfacial friction.When the bubble angle is 0°,the fluid boundary slip length is the largest and the solid-liquid interfacial friction is the smallest;the micro-nano structures affect the drag reduction characteristics and reducing solid-liquid contact can improve the drag reduction effect of superhydrophobic surface.According to the theoretical analysis results,we use one step immersion method and chemical replacement method to prepare the superhydrophobic surface with different micro-nano structures on metal.The experiment result shows that the superhydrophobic surface with conical structure has the best hydrophobicity and drag reduction effect.The prepared surface has water contact angle about 158° and the rolling angle about 4°.When it is in 1.5m/s velocity,the drag reduction rate is about 32%.Meanwhile,the superhydrophobic surface with conical structure has better durability.The surface still keep stable drag reduction effect when it is tested with rushing for 52 hours.So far,the methods of measuring solid-liquid interfacial friction are indirect measuring.These methods analyze the drag reduction at solid-liquid interface by the fluid slip length.The test result is always affected by liquid gravity.The paper suggests the method for direct measurement of weak frictional resistance of solid-liquid interface.We use the resistance sensor to build up the device for testing frictional resistance of solid-liquid interface.The testing device provides an experimental platform for the drag reduction.Based on the suggested test method for frictional resistance of solid-liquid interface,the prepared superhydrophobic surface and water frictional resistance are measured.We prove the model of cavitation drag reduction at solid-liquid interface with microstructure by the experiment.The preparation of superoleophobic surface is still the difficulty and it also restricts the study of drag reduction on superoleophobic surface.The paper suggests the composite method of electro deposition method and oxidation method to prepare the superoleophobic surface on copper.We analyze the influence of micro/nano structures on oleophobic and drag reduction effect.The study finds that compared with the common micro/nano structures,the hanging structure can reduce the actual surface connection of liquid and solid.The structure also can improve the oleophobic property and drag reduction.The prepared superoleophobic surface with hanging structure has oil contact ange about 156° and the rolling angle about 7°;meanwhile,the superoleophobic surface with hanging structure has well drag reduction effect and durability.When it is in 1.5 m/s velocity,drag reduction rate is about 23%.The surface still keep stable drag reduction effect when it is tested with rushing for 52 hours.Based on these,we prepare the superoleophobic surface on the rotor by compound method and study the rotor by the hydraulic floating support prototype.The experiment result shows that the superoleophobic surface can reduce the frictional resistance between rotor and oil and improve the speed of the rotor.更多还原