Study of Turbulent Drag Reduction Mechanisms in Dilute Polymer Solution by Using Micro Opto-imaging Technique

利用微观显示技术对链状聚合物稀溶液的湍流减阻机理进行了实验研究。它是基于暗视野显微镜。该系统采用市售的显微镜，配有干物镜（x40，NA0.75，WD0.51mm）或油浸物镜（x100，NA0.50 - 1.35，WD0.10mm）。照明由频闪或脉冲激光（25 mJ输出能量）与光纤光导一起提供。ICCD相机用于图像采集。本成像系统已成功地用于直径为800- 10 nm的标准胶乳颗粒的可视化;悬浮在载玻片和盖玻片之间形成的液体层中。通过将聚环氧乙烷（PEO，Alcox E-160）以50-500 ppm重量加入纯化水来制备稀链聚合物溶液。当溶液被夹在玻璃板之间时，受到适当的力的挤压，就会产生剪切应力。这导致 ...更多信息 成功地显示了在液体中拉伸的约20 μm长的单个链聚合物。通过构建一个由两块平行玻璃板组成的毫米级矩形通道，观察了PEO在静压差驱动下的湍流流动行为.照明是由脉冲Nd：YAG激光，以冻结PEO的行为在显微镜的放大视图。结果表明，本方法允许可视化的乳胶粒子，直径为150 nm，在湍流。然而，在湍流中PEO的行为的可视化中获得的图像质量不够高，这表明进一步优化本通道和暗场显微镜，以更好地微观可视化负责湍流减阻机制的分子行为。少

Experimental studies have been carried out to clarify turbulent drag reduction mechanisms in dilute chain polymer solution by using a micro visualization technique. It is based on the dark-field microscopy. The system employs a commercially available microscope equipped with a dry objective (x40,NA0.75,WD0.51mm) or an oil immersion objective (x100,NA0.50-1.35,WD0.10mm). Illumination is given by a strobe or a pulsed laser (25mJ output energy) together with fiber light guide. An ICCD camera is used for image acquisition. The present imaging system has successfully been used for visualization of standard latex particles, 800-10nm in diameter ; suspended in a liquid layer formed between a slide glass and a cover glass.Dilute chain polymer solutions are prepared by adding polyethyleneoxide (PEO, Alcox E-160) to purified water at 50-500 ppm at weight. Shear stress is given to the solutions when they are sandwiched by glass plates that are pressed by an appropriate force. This has resulted in … More a successful visualization of individual chain polymer, about 20 μm in length, stretched in the liquid. The 50 ppm solution shows the existence of isolated individual polymer molecule while the 500 ppm solution shows the existence of tangled structures of chain polymers.A millimeter-size rectangular channel formed by two parallel glass plates is constructed to visualize PEO's behaviors in a turbulent flow of 10m/s driven by a static pressure difference. Illumination is given by a pulsed Nd:YAG laser in order to freeze PEO'S behaviors in a magnified view of the microscope. It is shown that the present method permits visualization of latex particles, 150nm in diameter, in the turbulent flow. However, the image quality obtained in the visualization of PEO's behaviors in the turbulent flow is not sufficiently high, suggesting further optimization of the present channel and the dark-field microscope for better micro visualization of molecular behaviors responsible for the turbulent drag reduction mechanisms. Less