An experimental study has been conducted on unstable structures induced in two-dimensional slit flows of liquid crystalline polymer solution. aqueous solution of hydroxyl-propylcellulose (HPC) was utilized as a test fluid and its flow behavior in L-shaped slit channels with a cross section of height and width was measured optically. The inner corner of the L-shaped channel was rounded off in order to clarify the influence of the radius of curvature on the unstable behavior. A conversing curved channel was also tested. The flow patterns of the HPC solution in the channels were visualized with two crossed polarizers and we observed that typical wavy textures generated in the upstream of the corner almost disappeared after the corner flow. However, an unstable texture was developed again only from the inner corner in downstream flow. The fluctuation of the orientation angle and dichroism were also measured with a laser opto-rheometric system and it was found that the unstable behaviors of the HPC solution have periodic oscillatory characteristics at a typical frequency. In the inner side flow after the corner, the periodic motion became larger toward the downstream and then higher harmonic oscillations were superimposed. Larger rounding off of the inner corner suppressed the redevelopment of unstable behavior, and it is considered that the rapid regrowth of unstable behavior was caused by rapid deceleration at the corner flow. Moreover, the unstable structure was stabilized with an accelerated (elongated) region in the corner flow and the converging channel was helpful to obtain a stable structure in the downstream region.
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e-mail: narumi@eng.niigata-u.ac.jp
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August 2008
Research Papers
Flow Induced Unstable Structure of Liquid Crystalline Polymer Solution in L-Shaped Slit Channels
Takatsune Narumi,
Takatsune Narumi
Faculty of Engineering,
e-mail: narumi@eng.niigata-u.ac.jp
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, Japan
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Jun Fukada,
Jun Fukada
Graduate School of Science and Technology,
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, Japan
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Satoru Kiryu,
Satoru Kiryu
Graduate School of Science and Technology,
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, Japan
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Shinji Toga,
Shinji Toga
Graduate School of Science and Technology,
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, Japan
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Tomiichi Hasegawa
Tomiichi Hasegawa
Faculty of Engineering,
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, Japan
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Takatsune Narumi
Faculty of Engineering,
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, Japane-mail: narumi@eng.niigata-u.ac.jp
Jun Fukada
Graduate School of Science and Technology,
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, Japan
Satoru Kiryu
Graduate School of Science and Technology,
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, Japan
Shinji Toga
Graduate School of Science and Technology,
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, Japan
Tomiichi Hasegawa
Faculty of Engineering,
Niigata University
, 2-8050 Ikarashi, Nishi Ward, Niigata 950-2181, JapanJ. Fluids Eng. Aug 2008, 130(8): 081503 (6 pages)
Published Online: July 24, 2008
Article history
Received:
May 15, 2007
Revised:
August 28, 2007
Published:
July 24, 2008
Citation
Narumi, T., Fukada, J., Kiryu, S., Toga, S., and Hasegawa, T. (July 24, 2008). "Flow Induced Unstable Structure of Liquid Crystalline Polymer Solution in L-Shaped Slit Channels." ASME. J. Fluids Eng. August 2008; 130(8): 081503. https://doi.org/10.1115/1.2956604
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