Flow characteristics of water in hydrophobic micro cylinders group with different contact angles

Hydrophobic solution was prepared by adding 2% perfluorinated octyl fluorine silane and micro-nano particles to modified silicone dilute solution. This hydrophobic solution could be solidified to obtain hydrophobic surfaces, and the contact angle of water on these surfaces could be adjusted by changing the content of micro-nano particles in hydrophobic solution. Using the method above, different micro cylinders groups with contact angles of 99.5°, 119.5° and 151.5° (de-ionized water) were prepared, respectively. Using de-ionized water as working fluid, the flow resistance and pressure drops in micro cylinders groups with different contact angles were measured. The value of friction factor of test section with hydrophobic layer was apparently lower than that without the layer at the same Reynolds number, and this was because the surface tension on hydrophobic interaction interface led to a reduction of friction resistance. The larger the contact angle, the smaller the distance between the micro/nano bumps on the double structure of hydrophobic layer at the same Re, meanwhile the ratio of liquid-air contact area to the total flow area became higher, thus flow resistance decreased. The drag reduction rates attributed to the three kinds of hydrophobic coatings on surfaces of micro pin fins decreased continuously with the increase of Re. 2014-12-05收到初稿,2015-01-23收到修改稿。 联系人:刘志刚。第一作者:姜桂林(1981—),男,硕士,助理 研究员。 基金项目:国家自然科学基金项目 (51176105);山东省自然 科学基金项目( ZR2012EEQ015);山东省科技发展计划项目 (2014GGX104008)。 Received date: 2014-12-05. Corresponding author: Prof. LIU Zhigang, zgliu9322@163.com Foundation item: supported by the National Natural Science Foundation of China (51176105 ), the Natural Science Foundation of Shandong Province (ZR2012EEQ015), and the Shandong Province Science and Technology Development Plans (2014GGX104008). 第 5期 姜桂林等:水在不同接触角微柱群内的流动特征 ·1705·