• 대한기계학회논문집B
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• 제30권4호
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• pp.314-319
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• 2006

To analyze in-vivo blood flow characteristics in a chicken embryo, in-vivo experiment was carried out using micro-PIV technique. Because endothelial cells in blood vessels are subject to shear stress of blood flow, it is important to get velocity field information of the placental blood flow. Instantaneous velocity fields of an extraembryonic blood vessel using a high-speed camera and intravital microscope. The flow images of RBCs were obtained with a spatial resolution of $20\times20{\mu}m$ in the whole blood vessels. The mean velocity field data confirm that the blood flow does show non-Newtonian fluid characteristic. The blood in a branched vessel merged smoothly without any flow separation into the main blood vessel with the presence of a slight bump. This in-vivo micro-PIV measurement technique can be used as a powerful tool in various blood flow researches.

• 유변학
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• 제2권1호
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• pp.33-45
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• 1990

This study analyzes the planar 4:1 contraction flow of viscoelastic fluids with retardation time using finite volume method. To consider separately the elasticity effect of the viscoelastic fluid without shear thinn-ing effect, Oldroyd B liquid model is adopted for the numerical simulation. Instead of the stream function-vorticity formulation, SIMPLER algorithm with staggered grid system which incorporates primitive variable has been introduced in discretizing the momentum equations. An upwind corrected scheme has been used in discetizing the constitutive equations for the non-Newtonian part of the stress. The size of the corner vortex is shown to be slightly influenced by the Weissenberg number. However as the Weissenberg number is increased the chang-ing of the vortex shape agrees qualitatively well with some experimental studies.

• 산업기술연구
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• 제34권
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• pp.11-14
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• 2014

Viscosity and shear stress of the dental impression materials on commercial market(Imprint Garant LB(3M, U.S.A), EXAMIXFINE IT(GC, Japan), Vonflex S LB(Vericom, Korea), S-Silicone LB(Shinwon, Korea)) were measured with increasing shear rate from 50(1/sec) to 100(1/sec). The viscosity of EXAMIXFINE IT was decreased from 20,542(cP) to 14,684(cP), which is the shear thinning property of pseudoplastic as non-Newtonian fluid. Since the pseudoplastic property makes the impression material shear thinning and softly injected from cartridge, EXAMIXFINE IT might be popularly used in dentistry.

• 산업경영시스템학회지
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• 제29권1호
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• pp.151-154
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• 2006

The high degree of viscosity and the non-Newtonian fluid dynamics characterizes the process inside a glass furnace. Because the temperature is fluctuating in very short time-intervals, it is hard to determine that the status of its fluctuation is stable or unstable. Usually Shewhart-chart is used to determine the control status. However because of the characteristics of the temperature fluctuations in the glass furnace it does not directly serve the purpose here. Therefore we suggest using ARIMA to diagnose control status and confirm that the method using ARIMA can be a better tool than Shewhart-chart.

• 한국인쇄학회지
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• 제23권2호
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• pp.59-75
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• 2005

In gravure printing, the amount of ink from cells has a great effect on the qualities of final printed products. And printability of final products is determined by every kinds variables. Ink transfer process is not verified scientifically because gravure cell is of small size and print speed is rapid. Therefore in order to study of ink transfer mechanism, this study is using the Computational Fluid Dynamics Evaluation. Polyflow 3-10 simulation software is used for considering of non-Newtonian flow. Among the various factors, this study have dealt with gravure cell types used computer simulation in order to define distinctive features in ink flow and transfer. The results of simulation, it defined the distribution of pressure, speed, stream function, viscosity, shear rate during the gravure printing. It is fined out the difficulties and characteristics according to the shape of cell types. Through this study, the condition of gravure printing is depending on the print condition and characteristic of cells.

• 소성∙가공
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• 제14권6호
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• pp.570-576
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• 2005

Powder Injection Molding(PIM) has recently been recognized as an advanced manufacturing technology for low-cost mass production of metal or ceramic parts of complicated geometry With this regards, design technology of dental scaler tip PIM mold, which has complex shape and small core pin (diameter=0.6mm), with the help of computer-aided analysis of powder injection molding process was developed. Computer-aided analysis for dental scaler tip mold was implemented by finite element method with non-Newtonian fluid, modified Cross model viscosity, PvT data of powder/binder mixture. Compter-aided analysis results, such as filling pattern, weldline formation, air vent position prediction were compared with experimental result, and eventually have been shown good agreement. The core pin (diameter=0.6mm) deflection analysis of dental scaler tip PIM mold during PIM filling process was also investigated before mold fabrication.

• 대한기계학회논문집B
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• 제20권4호
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• pp.1501-1509
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• 1996

Differential pressure devices such as an orifice and Venturi are widely used in the measurement of flow rate of fluid mainly due to cost effectiveness and easy installation. In the current study, the viscoelastic effect on discharge and loss coefficients of those flow meters were investigated experimentally. Aqueous solutions of Polyacrylamide (200, 500, and 800 ppm) as viscoelastic fluids were used. Discharge coefficient of an orifice for viscoelastic fluids increased significantly up to approximately 15-20% when compared with that for water, while loss coefficient decreased up to 10-25% depending on the diameter ratio, .betha.. Also, pressure recovery for viscoelastic fluids was extended much longer than that for water. On the other hand, discharge and loss coefficients of Venturi for viscoelastic fluids were found to be strongly dependent on the Reynolds number. In both flow meters, the concentration effect for discharge and loss coefficients was not observed at more over than 200 ppm of aqueous solution. Conclusively, orifice and Venturi flow meters should be calibrated very carefully in the flow rate measurement for viscoelastic fluids.

• 공업화학
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• 제25권2호
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• pp.209-214
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• 2014

SDA (Solvent deasphalting)를 이용한 오일샌드 역청의 부분경질화 공정을 개발하기 위해 수행된 본 연구에서는 말텐에 대하여 포화탄화수소 용매의 종류, 용매 투입 비율, 온도, 전단속도 등에 따른 유변학적 거동과 비뉴톤 특성을 살펴보았다. 오일샌드 역청은 전단속도가 $50sec^{-1}$이고, 온도가 $25{\sim}85^{\circ}C$인 조건에서 $800{\sim}150000mPa{\cdot}s$의 겉보기 점도를 보이며, $35^{\circ}C$ 이하에서는 0.1~0.3 Pa의 항복응력을 나타냈다. 오일샌드와 말텐은 모두 Pseudoplastic의 특성을 보이고 포화탄화수소 용매의 탄소 수가 낮아질수록 말텐의 겉보기 점도는 감소하였다. 겉보기 점도와 온도와의 상관관계는 Guzman-Andrade식으로 나타낼 수 있었으며, n-Pentane의 투입 비율이 커짐에 따라 말텐의 점도가 감소하였다. 또한 온도가 높아질수록 말텐은 뉴톤 유체에 접근하였고, 용매로 사용된 포화탄화수소의 탄소 수가 작아질수록 비뉴톤 성질은 증가하였다.

• 대한기계학회논문집
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• 제17권5호
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• pp.1150-1160
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• 1993

본 연구에서는 보압과정시 급속한 압력구배에 의한 관성항의 영향을 고려하기 위해 수정된 Hele-Shaw 모델과 압축열 발생항, 온도와 압력의 변화에 따른 수지의 밀 도 이완현상에 대한 모델의 도입 및 유한요소법을 이용한 수치해석적 방법을 제시하여 정확한 잔류압력을 구하고 성형조건 및 물성치에 따른 수지의 거동을 살펴보고자 한다.

• 대한기계학회논문집A
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• 제30권1호
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• pp.32-41
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• 2006

We analyzed the non-Newtonian and non-isothermal flow in the melt conveying zone in co-rotating and counter-rotating screw extruder system with the commercial code, STAR-CD, and compared the mixing performance with respect to screw speed and rotating direction. The viscosity of fluid was described by power-law model. The dynamics of mixing was studied numerically by tracking the motion of particles in a twin screw extruder system. The extent of mixing was characterized in terms of the residence time distribution and average strain. The results showed that high screw speed decreases the residence time but increases the shear rate. Therefore higher screw speed increases the strain and has better mixing performance. Counter-rotating screw extruder system and co-rotating screw extruder has the similar shear rate with the same screw speed in spite of different rotating direction. However, the counter-rotating screw has good mixing performance, which is resulted from longer residence time than that of co-rotating screw extruder.