Nihon Reoroji Gakkaishi
Online ISSN : 2186-4586
Print ISSN : 0387-1533
ISSN-L : 0387-1533
Volume 40, Issue 2
Displaying 1-10 of 10 articles from this issue
FOREWORD
ORIGINAL ARTICLE
  • Takehiro Yamamoto, Junji Suzuki, Keisuke Taniguchi
    2012 Volume 40 Issue 2 Pages 55-60
    Published: May 15, 2012
    Released on J-STAGE: May 17, 2012
    JOURNAL FREE ACCESS
    In aqueous solutions of cetyltrimethylammonium bromide (CTAB), wormlike micelles are formed at concentrations above a critical micelle concentration. In addition when counter ion is added to a CTAB solution, wormlike micelles entangle to form networks, which have gel-like structures under some conditions. The present study investigates the formation of gel-like structures when an aqueous solution of sodium salicylate (NaSal) is injected into a flow of a CTAB solution in a circular channel. The condition at which the adhesion of gel to a channel wall occurs is relevant to both the concentration of NaSal and the flow velocity of CTAB solutions. When the concentration is high, the adhesion is observed even at high velocities. Experimental results imply that salicylate ions in injected fluids have an important role in both the adhesion and the growth phenomena of gel-like materials on the channel wall and these phenomena depend on the concentration of NaSal.
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  • Akiomi Ushida, Tomiichi Hasegawa, Masato Kawami, Hiroshige Uchiyama, T ...
    2012 Volume 40 Issue 2 Pages 61-68
    Published: May 15, 2012
    Released on J-STAGE: May 17, 2012
    JOURNAL FREE ACCESS
    Flows of microbubble/liquid mixtures have been extensively studied in both theoretical and applied research, and important results, such as drag reduction effects, have been reported. However, the majority of researchers have focused on only mixtures of microbubbles and water. Studies on microbubble mixtures in complex liquids, for example, for surfactant solutions and polymer solutions, are limited. The present study considers the flow of microbubble mixtures in a dilute polymer solution. In the present research, microbubbles (particle size: 20 μm) are suspended in either water or a dilute solution of polyethylene glycol. The liquids and suspensions were passed through various sizes of orifices (200 μm to 1.0 mm) and slits (397 μm and 596 μm), pressure drops were measured, and elongational stresses were estimated. Pressure drops of the polyethylene glycol solution were less than those of water, and the measured pressure drops of both microbubble mixtures were greater than those of the polyethylene glycol solution. As a result, polymer chains in the polyethylene glycol solution are considered to be laden with microbubbles, and this effect is seen in the corresponding elongational stress estimates.
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  • Shinji Tamano, Kotaro Miyagawa, Yohei Morinishi, Motoyuki Itoh, Keijir ...
    2012 Volume 40 Issue 2 Pages 69-77
    Published: May 15, 2012
    Released on J-STAGE: May 17, 2012
    JOURNAL FREE ACCESS
    We investigated effects of solution concentration C, solution temperature T, and degradation on drag reduction (DR) of nonionic surfactant aqueous solutions, which were non-toxic and biodegradable, by measuring the pressure drop and flow rate in the circuit pipe flow with the inner diameter of 25.1 mm. The maximum drag reduction ratio DRmax increased from about 70 % to 80 % with increasing from C = 50 to 1000 ppm at T ≈ 20 °C. The DRmax at C = 100 ppm was independent of the solution temperature T from 10 to 40 °C, while the region of Reynolds number at the large DR (> 60 %) was dependent on T. The degradation property strongly depended on whether the Reynolds number was smaller or larger than the critical Reynolds number, at which the DR was maximum. The drag-reducing effects obtained here were discussed as taking into account the strength of the shear thickening observed in the plot of shear viscosity vs. shear rate, which was measured by the homemade capillary viscometer.
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  • Yurika Kawai, Eiko Tamura, Toshiyuki Shikata, Tadashi Inoue
    2012 Volume 40 Issue 2 Pages 79-83
    Published: May 15, 2012
    Released on J-STAGE: May 17, 2012
    JOURNAL FREE ACCESS
    Simultaneous measurements of complex modulus and complex strain-optical (birefringence) coefficient were performed for silica particle suspensions in order to clarify the stress-optical relationship. The dynamic modulus was found to be described with three Maxwell models. The strain-optical coefficient changed its sign form positive to negative with increasing frequency, suggesting the coefficient was composed of two relaxation modes. The relationship between stress and birefringence were found to be described with the modified stress-optical rule, composed of two relaxation modes. The fast mode having negative birefringence was assigned to the anisotropic distribution of particles due to deformation. The slow mode having positive birefringence was tentatively assigned to the aggregation of particles. Although the examined particle dispersion system was not ideal it was strongly suggested that the stress-optical rule would hold valid for the ideal hard particle dispersion systems.
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  • Hiroshi Suzuki, Yuta Higuchi, Hirofumi Watanabe, Yoshiyuki Komoda, Sho ...
    2012 Volume 40 Issue 2 Pages 85-90
    Published: May 15, 2012
    Released on J-STAGE: May 17, 2012
    JOURNAL FREE ACCESS
    Experimental study on the relaxation behavior of the drag-reducing surfactant solution has been performed in order to investigate the mechanism of the drag reduction occurrence. The relaxation times and the drag reduction rates were measured in a wide range of the surfactant concentration and of the molar ratio of the counter-ions to surfactants. From the results, it was found that the present surfactant solution has at most three relaxation times in a middle range of the surfactant concentration and of the molar ratio. It was also found that the drag reduction occurs when the shortest relaxation time of 0.1 s exists. Thus, it was concluded that the existence of the shear-induced structure having this shortest relaxation time is important for the drag reduction occurrence.
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  • Tomohiko Anazawa, Takeaki Tsuda, Hiroshi Yoshiba, Takatsune Narumi, No ...
    2012 Volume 40 Issue 2 Pages 91-99
    Published: May 15, 2012
    Released on J-STAGE: May 17, 2012
    JOURNAL FREE ACCESS
    In this work, entrance flows of viscoelastic fluids from a cavity to a slot in a slot die coating were investigated experimentally and numerically. Aqueous solutions of polyethylene glycol (PEG) and polyethylene oxide (PEO) mixtures, having viscoelasticity and Newtonian viscosity, were tested in order to clarify the effects of viscoelastic characteristics to the excess pressure drops at the entrance. The measured excess pressure drop changes corresponded to the flow pattern changes from a Newtonian-like flow pattern to vortex generation and growth patterns in an asymmetric entrance flow with a submillimeter slot. Numerical predictions of the transitions in the flow patterns and the pressure drops were also made utilizing exponential Phan-Thien-Tanner (EPTT) model with a finite element method. The predictions qualitatively indicated the increase in excess pressure drop and the vortex generation and growth.
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  • Nono Darsono, Hiroshi Mizunuma, Hiromichi Obara
    2012 Volume 40 Issue 2 Pages 101-109
    Published: May 15, 2012
    Released on J-STAGE: May 17, 2012
    JOURNAL FREE ACCESS
    We herein describe our investigation of the rheological and electrical characteristics of single- and multi-walled carbon nanotube dispersions. The effect of the viscosity of the dispersing liquids was investigated under shear. At low shear rates, a dispersing liquid with a low viscosity caused the relative viscosity to increase more than a dispersing liquid with a high viscosity, in the case of single-walled carbon nanotube dispersions. The shear viscosity approached the same value regardless of the viscosity of the dispersing liquid. The independence of the shear viscosity suggests that at low shear rates it is dominated by the microstructure of the single-walled carbon nanotubes rather than the viscosity of the dispersing liquid. Extensional flow was produced by the capillary thinning of a liquid thread, and both the apparent extensional viscosity and the electrical conductivity were measured for the carbon nanotube dispersions. During capillary thinning, the apparent extensional viscosity approached the theoretical extensional viscosity predicted by Batchelor for low concentrations, but was notably higher than the theoretical values predicted for high concentrations. The electrical conductivity was increased via the stretching of the threads and the solidification of the dispersing photopolymer. The concentration at the electrical percolation threshold was approximately the same as the concentration at which the apparent extensional viscosity deviated from the theoretical prediction of Batchelor. A network structure of carbon nanotubes is herein suggested to increase the apparent extensional viscosity at concentrations above the percolation threshold.
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  • Tomohiro Shimizu, Takehiro Yamamoto
    2012 Volume 40 Issue 2 Pages 111-116
    Published: May 15, 2012
    Released on J-STAGE: May 17, 2012
    JOURNAL FREE ACCESS
    A micro-macro computational approach was applied to a numerical simulation for slot coating flows of concentrated dispersion system of disclike particles. In the present simulation, the computation of macro flows was coupled with the micro simulation of dynamics of dispersed particles. Disc like particles were modeled by oblate spheroids, and the effect of interaction among particles was introduced using a Maier-Saupe type mean field potential. The Brownian configuration field method was used for solving the stochastic differential equation of particle motion. The numerical results indicated that particles were aligned well near the exit of a die and the particle orientation relaxed along the flow. The orientation order was larger for higher Peclet number. Furthermore, the orientation distribution was obtained from the numerical prediction of the orientation vector of each particle.
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