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Volume 37 (2009)
- Issue 5 Pages 211-
- Issue 4 Pages 173-
- Issue 3 Pages 121-
- Issue 2 Pages 57-
- Issue 1 Pages 1-
Volume 37, Issue 4
Displaying 1-5 of 5 articles from this issue
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Original Articles
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Navid Khabazi, Kayvan Sadeghy2009 Volume 37 Issue 4 Pages 173-180
Published: September 15, 2009
Released on J-STAGE: December 12, 2009
JOURNAL FREE ACCESSThe effect of a fluid's elasticity is investigated on the instability of Blasius flow at the presence of a transverse magnetic field. To determine the critical Reynolds number as a function of the elasticity and magnetic numbers, a two-dimensional linear temporal stability analysis is used assuming that the viscoelastic fluid of interest obeys Walters' B model as its constitutive equation. Neglecting terms nonlinear in the perturbation quantities, an eigenvalue problem is obtained which is solved numerically using the Chebychev collocation method. Based on the results obtained in this work, fluid's elasticity is predicted to have a destabilizing effect on Blasius flow. In contrast, the effect of the magnetic field is predicted to be always stabilizing in Blasius flow, at least in the range of parameters used in this work.View full abstractDownload PDF (681K) -
Mostafa Esmaeili, Kayvan Sadeghy2009 Volume 37 Issue 4 Pages 181-189
Published: September 15, 2009
Released on J-STAGE: December 12, 2009
JOURNAL FREE ACCESSIn the present study, the effect of a transverse magnetic field is investigated on the flow separation phenomenon at the lee of a single, two-dimensional symmetric constriction assuming that the fluid of interest is of the power-law type. For steady, two-dimensional, and incompressible flow, the equations of motion will be solved using the finite volume formulation based on a staggered grid. Numerical results obtained for the velocity and pressure fields suggest that flow separation occurring downstream the constriction can be controlled by manipulating the degree of the shear-thinning behavior of the fluid and/or by applying an external magnetic field. That is, the size of the separation bubble formed in flow through constrictions is predicted to decrease by an increase in the power-law exponent and/or the strength of the externally imposed magnetic field. The wall shear stress is also predicted to increase by an increase in the strength of the magnetic field.View full abstractDownload PDF (1986K) -
Emi Hasegawa, Hiroshi Suzuki, Yoshiyuki Komoda, Hiromoto Usui2009 Volume 37 Issue 4 Pages 191-198
Published: September 15, 2009
Released on J-STAGE: December 12, 2009
JOURNAL FREE ACCESSA model estimating the time-dependent distribution of cluster size consisting of fine particles in Newtonian molten polymer has been improved. The present model for agglomerative suspension was developed based on Usui's thixotropy model, derived by taking the balance between shear breakup, shear coagulation and Brownian coagulation process. The interparticle bonding energy in the model was assumed as a function of a cluster size in this study though it was assumed to be constant in the previous study. The analysis was applied to the experimental results for silica/(ethylene methyl-meta acrylate copolymer) suspensions. The time variation of cluster size distributions, of viscosities and of the mean number of particles in a cluster was calculated and the results were compared with experimental results mainly for the cases of the solid volume fractions from 0.10 to 0.25 when the shear rate was changed from 0.2 to 10 s-1. From the results, it was found that the present model could estimate well the time dependency of cluster size distributions in a wide range of shear rate when the solid volume fraction was set at 0.15, and that the effect of the solid volume fraction was also sufficiently explained by the present model.View full abstractDownload PDF (868K) -
Kazuhiko Matsumura, Hiroshi Yamaguchi2009 Volume 37 Issue 4 Pages 199-204
Published: September 15, 2009
Released on J-STAGE: December 12, 2009
JOURNAL FREE ACCESSIn the present study various magneto-rheological elastomers, which are mixtures with ferromagnetic particles and silicone gel, are introduced in order to develop a new type of magnetic viscoelastic material. Such materials, in view of industrial application, require substantial change of mechanical properties to create a large deformation due to magnetic traction force when even a moderate strength of magnetic field is imposed. In this study, in particular tensile tests for various magneto-rheological elastomers were performed and reported under uniform steady magnetic field. In order to clarify the rheological parameter, the elastic moduli of the elastomers are obtained under tensile strain deformation. As results of the experiment, it was found that at the presence of the applied magnetic field, the elastic moduli of the magneto-rheological elastomers increase and are largely dependent upon magnetic property and size of the magnetic particle to be dispersed, and also upon materials of the dispersant, the silicone gel. The most appropriate combination of those, within the materials used in the present investigation, is discussed in view of gaining large magnetic traction force, which effectively gives large material deformation under applied field.View full abstractDownload PDF (1968K) -
Chieko Hayashi, Tadashi Inoue2009 Volume 37 Issue 4 Pages 205-210
Published: September 15, 2009
Released on J-STAGE: December 12, 2009
JOURNAL FREE ACCESSA new apparatus for simultaneous measurements of dynamic birefringence and dynamic viscoelasticity under oscillatory shear flow was developed with an oblique laser beam. Reliability of the apparatus was confirmed with the measurements on polystyrene solution and polystyrene melt, for which the stress-optical rule is known to hold valid. The values of the estimated stress-optical coefficient were reasonably in accord with the literature data. The measurement on a model supramolecular system having a linear thread-like shape showed that the breakdown of stress-optical rule at high frequencies, suggesting that this supramolecular system cannot be regarded as a simple ordinary polymeric system. This preliminary result indicates the promised advantage of the apparatus to discuss the molecular origin of the stress for complex systems.View full abstractDownload PDF (989K)
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