2004 Fiscal Year Final Research Report Summary
Study of Turbulent Drag Reduction Mechanisms in Dilute Polymer Solution by Using Micro Opto-imaging Technique
| Project/Area Number |
15360093
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fluid engineering
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| Research Institution | Yokohama National University |
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Principal Investigator |
NISHINO Koichi Yokohama National University, School of Engineering, Professor, 大学院・工学研究院, 教授 (90192690)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Flow Visualization / Turbulence / High Polymer Solution / Drag Reduction / Toms Effect / Micro Visualization / Dark-field Microscopy |
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| Research Abstract |
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
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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
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