• 대한의용생체공학회:의공학회지
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• 제18권2호
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• pp.187-196
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• 1997

The three-dimensional flow analysis using the finite volume method is presented to compare the steady flow characteristics of blood with those of blood substitutes such as water and aqueous polymer solution in an idealized double branching model. The model is used to simlllate the region of the abdominal aorta near the celiac and superior mesenteric branches. Apparent viscosities of blood and the aqueous Separan solution are represented as a function of shear rate by the Carreau model, Water and aqueoiu Separan AP-273 500wppm solution are frequently used as blood substitutes in vitro experiments. Water is a typical Newtonian fluid and blood and Separan solution are non-Newtonian fluids. Flow phenomena such as velocity distribution, pressure variation and wall shear stress distribution of water, blood and polymer solution are quite different due to differences of the rheological characteristics of fluids. Flow phenomena of polymer solution are qualitatively similar to those of blood but the phenomena of water are quite different from those of blood and polymer solution. It is recommended that a lion-Newtonian fluid which exhibits very similar rheological behavior to blood be used in vitro experiments. A non-Newtonian fluid whose rheological characteristics are very similar to those of blood should be used to obtain the meaninylll hemodynamic data for blood flow in vitro experiment and by numerical analysis

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1037-1049
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• 2001

Considerable interest has evolved in the flow of non-Newtonian fluids in channels of noncircular cross section in compact heat exchanges. Analytical solution was developed for prediction of the flow rate and maximum velocity in steady laminar flow of any incompressible, time-independent non-Newtonian fluids in straight closed and open channels of arbitrary, but axially unchanging cross section. The geometric parameters and function of shear describing the behavior of the fluid model were evaluated for fluid flow among a bundle of rods arranged in triangular and square array. Numerical values of dimensionless maximum velocities, mean velocities, pressure-drop-flow parameters and friction factors were evaluated as a function of porosity and pitch-to-radius ratio.

• Korea-Australia Rheology Journal
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• 제21권4호
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• pp.269-280
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• 2009

The drop formation dynamics of a shear thinning, elastic, yield stress ($\tau_o$) fluid (Carbopol 980 (poly(acrylic acid)) dispersions) in silicone oil has been investigated in a flow-focusing microfluidic channel. The rheological character of each solution investigated varied from Netwonian-like through to highly non-Newtonian and was varied by changing the degree of neutralization along the poly (acrylic acid) backbone. We have observed that the drop size of these non-Newtonian fluids (regardless of the degree of neutralisation) showed bimodal behaviour. At first we observed increases in drop size with increasing viscosity ratio (viscosity ratio=viscosity of dispersed phase (DP)/viscosity of continuous phase (CP)) at low flowrates of the continuous phases, and thereafter, decreasing drop sizes as the flow rate of the CP increases past a critical value. Only at the onset of pinching and during the high extensional deformation during pinch-off of a drop are any differences in the non-Newtonian characteristics of these fluids, that is extents of shear thinning, elasticity and yield stress ($\tau_o$), apparent. Changes in these break-off dynamics resulted in the observed differences in the number and size distribution of secondary drops during pinch-off for both fluid classes, Newtonian-like and non-Newtonian fluids. In the case of the Newtonian-like drops, a secondary drop was generated by the onset of necking and breakup at both ends of the filament, akin to end-pinching behavior. This pinch-off behavior was observed to be unaffected by changes in viscosity ratio, over the range explored. Meanwhile, in the case of the non-Newtonian solutions, discrete differences in behaviour were observed, believed to be attributable to each of the non-Newtonian properties of shear thinning, elasticity and yield stress. The presence of a yield stress ($\tau_o$), when coupled with slow flow rates or low viscosities of the CP, reduced the drop size compared to the Newtonian-like Carbopol dispersions of much lower viscosity. The presence of shear thinning resulted in a rapid necking event post onset, a decrease in primary droplet size and, in some cases, an increase in the rate of drop production. The presence of elasticity during the extensional flow imposed by the necking event allowed for the extended maintenance of the filament, as observed previously for dilute solutions of linear polymers during drop break-up.

• 청정기술
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• 제14권4호
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• pp.281-286
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• 2008

Polyacrylamide (PAA) 수용액의 유변학적 특성이 $CO_2$의 흡수속도에 미치는 영향을 고찰하기 위해 $25^{\circ}C$, 1기압에서 평판조의 흡수기(교반조의 임펠러 크기 0.05 m, 교반속도 50 rpm)를 사용하여 PAA 수용액에 $CO_2$의 흡수실험을 행하였다. 제시한 Deborah수와 $CO_2$의 물질전달계수와의 상관관계식으로부터 물질전달계수를 구하여 triethanolamine을 첨가한 PAA수용액에서 $CO_2$의 화학흡수속도의 산출에 사용하였다. PAA수용액에서 $CO_2$의 흡수속도는 동일점도의 기준에서 뉴튼액체에서의 값보다 감소하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제16권3호
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• pp.181-192
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• 2012

Here in this paper, the steady paint film flow on a vertical wall of a non-Newtonian pseudo plastic fluid for drainage problem has been investigated. The exact solution of the nonlinear problem is obtained for the velocity profile. Also the average velocity, volume flux, shear stress on the wall, force to hold the wall in position and normal stress difference have been derived. We retrieve Newtonian case, when material constant ${\mu}_1$ and relaxation time ${\lambda}_1$ equal zero. The results for co-rotational Maxwell fluid is also obtained by taking material constant ${\mu}_1$ = 0. The effect of the zero shear viscosity ${\eta}_0$, the material constant ${\mu}_1$, the relaxation time ${\lambda}_1$ and gravitational force on the velocity profile for drainage problem are discussed and plotted.

• Journal of Magnetics
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• 제21권3호
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• pp.468-475
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• 2016

In this article, entropy generation on MHD Williamson nanofluid over a porous shrinking sheet has been analyzed. Nonlinear thermal radiation and chemical reaction effects are also taken into account with the help of energy and concentration equation. The fluid is electrically conducting by an external applied magnetic field while the induced magnetic field is assumed to be negligible due to small magnetic Reynolds number. The governing equations are first converted into the dimensionless expression with the help of similarity transformation variables. The solution of the highly nonlinear coupled ordinary differential equation has been obtained with the combination of Successive linearization method (SLM) and Chebyshev spectral collocation method. Influence of all the emerging parameters on entropy profile, temperature profile and concentration profile are plotted and discussed. Nusselt number and Sherwood number are also computed and analyzed. It is observed that entropy profile increases for all the physical parameters. Moreover, it is found that when the fluid depicts non-Newtonian (Williamson fluid) behavior then it causes reduction in the velocity of fluid, however, non-Newtonian behavior enhances the temperature and nanoparticle concentration profile.

• 천문학회지
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• 제46권2호
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• pp.93-96
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• 2013

Modified Newtonian Dynamics (MOND) is a possible solution for the missing mass problem in galactic dynamics; its predictions are in good agreement with observations in the limit of weak accelerations. However, MOND does not derive from a physical mechanism and does not make predictions on the transitional regime from Newtonian to modified dynamics; rather, empirical transition functions have to be constructed from the boundary conditions and comparisons with observations. I compare the formalism of classical MOND to the scaling law derived from a toy model of gravity based on virtual massive gravitons (the "graviton picture") which I proposed recently. I conclude that MOND naturally derives from the "graviton picture" at least for the case of non-relativistic, highly symmetric dynamical systems. This suggests that-to first order-the "graviton picture" indeed provides a valid candidate for the physical mechanism behind MOND and gravity on galactic scales in general.

• 기술사
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• 제4권15호
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• pp.11-15
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• 1971

Bunker C fuel oil may be taken as a conc. solution of asphalt as a solute. It may be assumpt that there will be unalogical relationship between cone. solution and solute in regological behavior. Investigation was carried out to fiud out the -opitimum preheating temperature. The following results were obtained: the colloidal structure bunker C fuel oil undergoes a transition at around the softening point of the solute asphalt: and the flow charactor changes from non-Newtonian flow to Newtonian as well as its activation energy is memarkably reduced at around softening point of the solute asphalt for the purpose of the improvement of flow charater of Bunker C fuel oil, the preheating must be done above the softening point of a solute asphalt.

• Korea-Australia Rheology Journal
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• 제21권2호
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• pp.109-117
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• 2009

Absorption rate of carbon dioxide was measured in the aqueous xanthan gum (XG) solution in the range of 0~0.15 wt% containing diisopropanolamine (DIPA) of $0{\sim}2\;kmol/m^3$ in a flat-stirred vessel with an impeller of 0.05 m and agitation speed of 50 rpm at $25^{\circ}C$ and 101.3 kPa. The volumetric liquid-side mass transfer coefficient ($k_La$) of $CO_2$, which was obtained by the measured physical absorption rate, was correlated with the viscosity and the elastic behavior of XG solution such as Deborah number as an empirical formula. The chemical absorption rate of $CO_2$ ($R_A$), which was estimated by the film theory using the measured $k_La$ and the known kinetics of reaction between $CO_2$ and DIPA, was compared with the measured rate. The aqueous XG solution with elastic property of non-Newtonian liquid made $k_La$ and $R_A$ increased compared with Newtonian liquid based on the same viscosity of the solution.

• Korea-Australia Rheology Journal
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• 제20권1호
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• pp.1-6
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• 2008

Absorption rate of carbon dioxide was measured in the aqueous xanthan gum (XG) solution in the range of 0-0.15 wt% containing 2-amino-2-methyl-1-propanol (AMP) of $0-2\;kmol/m^3$ in a flat-stirred vessel with an impeller of 0.05m and agitation speed of 50rpm at $25^{\circ}C$ and 0.101 MPa. The volumetric liquid-side mass transfer coefficient ($k_La$) of $CO_2$, which was correlated with the viscosity and the elastic behavior of XG solution containing Deborah number as an empirical formula, was used to estimate the chemical absorption rate of $CO_2\;(R_A)$. $R_A$, which was estimated by mass transfer mechanism based on the film theory using the physicochemical properties and the kinetics of reaction between $CO_2$ and AMP, was compared with the measured rate. The aqueous XG solution with elastic property of non-Newtonian liquid made $R_A$ increased compared with Newtonian liquid based on the same viscosity of the solution.