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Interfacial instability of Boger fluid in the pull-off test between two circular plates
Chongyoup Kim,Hyoung Mi Kang 한국유변학회 2004 Korea-Australia rheology journal Vol.16 No.4
In this study the deformation of liquid-air interface of Newtonian or Boger fluids filled between two parallel-plates geometry was investigated when two surfaces were separated at a constant speed. The interface between the fluid and air showed either stable or unstable deformation depending on experimental conditions. Repeated experiments for a wide range of experimental conditions revealed that the deformation mode could be classified into three types: 'stable region', 'fingering' and 'cavitation'. The experimental condition for the mode of deformation was plotted in a Capillary number vs. Deborah number phase plane. It has been found that the elasticity of Boger fluids destabilize the interface deformation. On the other hand, the elasticity suppresses the formation and growth of cavities.
( Chongyoup Kim ),( Jongeoun Hong ),( Suhyun Kim ),( Hakhee Kang ) 대한화장품학회 1999 대한화장품학회지 Vol.25 No.4
Liquid crystal known as a rheological barrier to coalescence of oil droplets, increases emulsion stability, water-holding capacity and promotes active material penetration to skin. Some investigation for its rheological characteristics have been reported but its relations to consumer perception have been rarely published. In this study. oil/watcr emulsion and oil/liquid cryslal/water systems were manufactured using the same composition of Bechenyltrimethylammonium chloride/(Cetostearyl alcohol/Lanolin oil and rheological properties each system were investigated with Cone and Plate rheometer. The formation of liquid crystalline phase was observed with polarized microscope and Differential Scanning Calorimeter. Continuous shear experiment, creep, yield and water holding capacity were measured for oil/water and oil/liquid crystal/water systems. The results were compared with sensory evaluations. ()il/liquid crystal/water system ‘showed higher .viscosity at the same shear rate, higher viseoeLasticity and higher yield stress than oil/water system. These properties were expected to show good spreadability and exceilent richness without waxiness in hair care products of creme type. This expectation was consistent with the results of sensory experiments. Water-holding capacity was evaluation by measuring residual water of specimens at specilie temperature and relative humidity. Oil/liquid cryslal/walcr system was proved to have higher ability lo hold writer in comparison with oil/water system. The results indicated that oii/Iiquid cryslal/water system was of benefit to rheological properties creme type hair care producls.
Migration in concentrated suspension of spherical particles dispersed in polymer solution
Kim, Chongyoup The Korean Society of Rheology 2001 Korea-Australia rheology journal Vol.13 No.1
In this symposium paper, the migration and hydrodynamic diffusion of non-colloidal, spherical particles suspended in polymer solutions are considered under Poiseuille or torsional flows. The migration phenomena in polymer solutions are compared with those in Newtonian fluids and the effect of fluid elasticity is discussed. The experimental results on particle migration in dilute polymer solution reveal that even a slight change in the rheological property of the dispersing medium can induce drastic differences in flow behavior and migration of particles, especially in dilute and semi-concentrated suspensions.
Kim, Chongyoup 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.1
In this paper, a mathematical model is considered of the migration of non-colloidal, spherical particles suspended in Newtonian fluid under Poiseuille flows by combining the inertial migration theory by Ho and Leal (JFM, 1974) and particle migration model in concentrated suspension by Phillips et al. (Phys. Fluids, 1992). The numerical solutions of the model equations reveal that the model set up here explains the experimental observation reported in the literature when Re_(p)<1, at least qualitatively. It was concluded that both the inertia and particle-particle interaction should be taken into account properly to understand the particle migration in tube flow of suspension regardless of particle loading.
Study on the growth of vapor bubble in devolatilization of polymers
Kim, Chongyoup The Korean Society of Rheology 1999 Korea-Australia rheology journal Vol.11 No.3
The growth of a spherical vapor bubble contained in a large body of upper convected Maxwell fluid is theoretically analyzed under the devolatilization condition of polymer by using a Galerkin FEM in the Lagrangian frame. Using the finite element technique, a fully explicit numerical scheme is developed both for the calculation of pressure distribution and for the tracking of bubble surface. Oscillatory behavior in bubble radius is observed during growth and the oscillatory behavior is found to be due to the interaction of mass transfer resistance and elasticity. It is found that the elasticity of fluid accelerates the growth and removal of volatile component. It is also found that the bubble growth in the devolatilization of polymers is affected by both mass transfer resistance and viscoelasticity of fluids.