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Volume 41 (2013)
- Issue 5 Pages 271-
- Issue 4 Pages 187-
- Issue 3 Pages 113-
- Issue 2 Pages 45-
- Issue 1 Pages 1-
Volume 41, Issue 5
Displaying 1-8 of 8 articles from this issue
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AWARD LECTURE ARTICLES
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Atsushi Takahara2014 Volume 41 Issue 5 Pages 271-281
Published: January 15, 2014
Released on J-STAGE: January 12, 2014
JOURNAL FREE ACCESSSurface and interfacial dynamics and surface mechanical properties are important for both fundamental and practical aspects. In this paper, our recent researches on 1) surface molecular motion and frictional properties of organosilane monolayer immobilized on Si-substrate, 2) characterization of mechanical and thermal properties buried interface in multiphase polymer thin films by scanning force microscopy, 3) wettability, friction, and adhesion of polymer brushes, and 4) application of X-ray photon correlation spectroscopy for soft materials are summarized.View full abstractDownload PDF (2391K)
AWARD LECTURE ARTICLES
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Sathish K. Sukumaran2014 Volume 41 Issue 5 Pages 283-287
Published: January 15, 2014
Released on J-STAGE: January 12, 2014
JOURNAL FREE ACCESSThe dynamics of chains in entangled polymeric liquids and its relationship to the macroscopic rheological properties is of both fundamental and industrial interest. One approach that has proven quite illuminating is to investigate the motion of relatively simple, bead-spring type, polymer model chains simulated on a computer using the molecular dynamics technique. In order to highlight the power and the potential of molecular dynamics simulations, I will provide two illustrations of the use of molecular dynamics to elucidate aspects of entangled polymer liquids. The first will deal with the relationship between the structure of a polymer melt and a physical property that is determined by the topological constraints experienced by a chain in the melt, the plateau modulus. The second will deal with the use of molecular dynamics to obtain adequately detailed information to perform a rigorous test of the ability of a single chain model to describe the dynamics and rheology of entangled polymer liquids in the linear regime.View full abstractDownload PDF (821K) -
Shinji Tamano2014 Volume 41 Issue 5 Pages 289-300
Published: January 15, 2014
Released on J-STAGE: January 12, 2014
JOURNAL FREE ACCESSThe unsteady flow behavior and turbulent drag reduction were investigated experimentally and numerically. Regarding unsteady swirling flows of aqueous polymer solutions due to a rotating disc in a cylindrical casing, we found a new phenomenon of vortex shedding in which the ring vortex formed near the rotating disc was periodically shed away from the rotating disc. The numerical simulation of the confined swirling flow was also performed at low Reynolds numbers, in which the Giesekus model was used as a constitutive equation. For drag-reducing turbulent boundary layers of aqueous cationic and nonionic surfactant solutions, turbulence statistics and structures were investigated by the LDV and PIV systems. For the cationic surfactant solution, the additional maximum of the streamwise turbulence intensity near the center of boundary layer was explained by the bilayered structure model. The mechanism of the drag reduction was investigated by the direct numerical simulation of viscoelastic fluids.View full abstractDownload PDF (4244K) -
Yasuya Nakayama2014 Volume 41 Issue 5 Pages 301-307
Published: January 15, 2014
Released on J-STAGE: January 12, 2014
JOURNAL FREE ACCESSDepartment of Chemical Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
Most complex fluids are characterized different disparities: disparity of sizes of components as in colloidal dispersions, disparity of viscosity typically found in blends, disparity of relaxation times, and so on. Furthermore, most complex fluids are characterized by specific properties of interfaces. One important application of the rheology of complex fluids is melt-mixing process as used in polymer industries, food processing and pharmaceutical industries. We present a summary on our studies including a direct numerical simulation for colloidal dispersions in complex solvents which is called “Smoothed Profile method” (Phys. Rev. E 71, 036707 (2005);Phys. Rev. Lett.,96, 208302 (2006);Eur. Phys. J. E, 26, 361 (2008)), a characterization of melt-mixing process in a twin-screw extruder (Chem. Eng. Sci., 66, 103 (2011)), and dynamic shear response of melt polymer-polymer interfaces (Nihon Reoroji Gakkaishi, 40, 245 (2012)).View full abstractDownload PDF (1555K)
ORIGINAL ARTICLES
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A. Ahmadpour, H. Amini-Kafiabad, K. Sadeghy2014 Volume 41 Issue 5 Pages 309-318
Published: January 15, 2014
Released on J-STAGE: January 12, 2014
JOURNAL FREE ACCESSIn the present work, the dynamics of a single spherical gas bubble surrounded by an elastic thixotropic liquid is addressed at the presence of an acoustic pressure field. The well-known Dullaert and Mewis' rheological model is used to represent different aspects of the fluid's thixotropic and elastic behavior. A numerical method based on Gauss-Laguerre quadrature is adopted to integrate the integro-differential equation governing bubble dynamics. The numerical results suggest that bubble response is significantly affected by the thixotropic properties of the surrounding fluid. A competition between the time constant set forth by the fluid's elasticity and the time constant related to the fluid's thixotropicity is predicted to give rise to the generation of second harmonics in the bubble's response for certain range of model parameters.View full abstractDownload PDF (1404K) -
M. Vahabi, K. Sadeghy2014 Volume 41 Issue 5 Pages 319-329
Published: January 15, 2014
Released on J-STAGE: January 12, 2014
JOURNAL FREE ACCESSRising of a single bubble in Newtonian and non-Newtonian fluid is numerically studied by weakly-compressible SPH method. In order to model different bubble rising regimes, various modifications are made to the existing WC-SPH algorithm. Several simulations are performed to investigate the effects of Re and Bo numbers. It is shown that the method is robust enough for simulating two-phase flows with density ratios as large as 1,000, and viscosity ratios as large as 20,000. Simulations are done assuming that the surrounding liquid is a purely-viscous shear-thinning fluid obeying the Carreau-Yasuda model. Based on the numerical results obtained in this work, shear-thinning is predicted to dramatically affect the bubble shape. It is shown that in a shear-thinning fluid, bubble moves more easily with a shape which is more oblate.View full abstractDownload PDF (4684K) -
Liwei Yu, Daisuke Tatsumi, Mitsuhiro Morita2014 Volume 41 Issue 5 Pages 331-336
Published: January 15, 2014
Released on J-STAGE: January 12, 2014
JOURNAL FREE ACCESSCellulose fibers were carbonized at 900 °C to make fiber networks having conducting properties. Dynamic viscoelasticity and electrical conductivity of the conductive fiber networks were examined. The storage modulus, G', of the networks increased with the network concentration, c, and a power law was found between G' and c: G' = kcα. The exponent, α, was almost the same as that of the other power law for non-carbonized cellulose fiber networks. The electrical conductivity, σ, of the conductive fiber networks also increased with c, and another power law was found between σ and c: σ = k'cβ. The value of exponent, β, was almost the same as α. The coincidence of the exponents for the power law relationships indicates that both of the viscoelastic and electric behaviors of the networks were expressed with the same formula attributed to transfer phenomena, that is momentum and electron transfer, respectively.View full abstractDownload PDF (1770K)
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Takashi Koshiba, Takehiro Yamamoto2014 Volume 41 Issue 5 Pages 337-340
Published: January 15, 2014
Released on J-STAGE: January 12, 2014
JOURNAL FREE ACCESSWe investigated rheological properties of surfactant solutions including a small amount of organic additives, and discussed the effect of additives on the structural transformation of micelles. Test fluids used were mixtures of an aqueous solution of CTAB/NaSal and 2,2,4-trimethylpentane (isooctane). The ratio of NaSal to CTAB (0.03 mol/l) was 7.7 and the concentrations of isooctane to the surfactant solution were 0.01 wt% and 0.1 wt%. In measurements of linear viscoelasticity, it was found that the dynamical property of fluids including additives was described by a single mode Maxwell model. However, the relaxation time decreased with the increase in isooctane concentration. Such change in relaxation time was related to the solubilization of organic additives into micelles, which weakened the mechanical strength of micelles. Furthermore, viscosity curves showed that the structural transformation from a wormlike micelle to a spherical one occurred. In experiments of small angle light scattering in shear flow, the comparison of scattering patterns between a fluid with additives and that without additives captured differences due to the structural transformation. In addition, it was found that the isooctane in solution took a spherical structure, which distributed in a wide range of diameter.View full abstractDownload PDF (842K)
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