• Title, Summary, Keyword: shear thinning

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NUMERICAL STUDY OF THE DROPLET EJECTION BEHAVIOR OF NEWTONIAN AND SHEAR-THINNING FLUIDS (뉴튼유체와 전단희석유체의 액적분사 거동에 대한 수치해석적 연구)

  • Kim, E.;Baek, J.
    • Journal of computational fluids engineering
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    • v.17 no.3
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    • pp.33-38
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    • 2012
  • The droplet ejection behavior from drop-on-demand printhead are investigated numerically for Newtonian and shear-thinning fluid. The numerical simulation is performed using a volume-of-fluid model. In this study, we compare the printable range in terms of Z number and pinch-off time for Newtonian and shear-thinning fluids. The printability range are found to be 1.08 $$\leq_-$$ Z $$\leq_-$$ 12.9 for Newtonian fluid and 0.8 $$\leq_-$$ Z $$\leq_-$$ 12.9 for shear-thinning fluid. However, air entrainment is observed during merging of primary and satellite droplet within the printability range. The pinch-off time of the shear-thinning fluid is apparently shorter compared to the corresponding Newtonian fluid due to shear-thinning effects and the differences in the pinch-off time is enlarged significantly when the capillary number is larger than 0.5.

Characteristics of Shear-Thinning Fluid Viscosity under Traversal Vibration (진동장에서의 전단박화 유체 점도의 특성 연구)

  • Ku Yun-Hee;Lee Ji-Hyung;Shin Sehyun
    • Proceedings of the KSME Conference
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    • pp.317-320
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    • 2002
  • The effect of vibration on the viscosity of a shear-thinning fluid was investigated with a newly designed pressure-scanning capillary viscometer. The viscometer was designed to measure non-Newtonian viscosity continuously over a range of shear rates at a time. Low frequency vibration was applied perpendicularly to the direction of the flow. The effect of the transversal vibration was investigated for both Newtonian fluids and non-Newtonian fluids. The experimental results showed that the vibration had no effect on the viscosity of the Newtonian fluids. However, the vibration caused a significant reduction of the shear-thinning fluid viscosity. The viscosity reduction was strongly dependent on both vibration frequency and shear rate. In addition, the viscosity reduction was affected by the amplitude of vibration, and, the bigger amplitude applied, the more viscosity reduction occurred.

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A Study on Heat Transfer Enhancement for a Shear-Thinning Fluid in Triangular Ducts (삼각형 단면 덕트 내의 Shear-Thinning 유체에 대한 열전달 촉진에 관한 연구)

  • Lee, Dong-Ryul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.9
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    • pp.3808-3814
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    • 2011
  • The prediction of heat transfer and pressure drops in the exchanger passages is a clue to the problem of heat exchanger design. In order to make such predictions for non-Newtonian fluids, it is necessary to know the relation between the viscous properties of the fluid and the wall shear rate in the duct. This study deals with the limits of validity of the power law equation. The useful methodology of the present research involves a consideration of a more general equation which has power law and Newtonian behavior as asymptotes. It isconcluded that use of the power law equation outside of its applicability range can lead to serious errors inpredicting the heat transfer and pressure drops. The present computational results of the friction factors times Reynolds number for shear-thinning fluid flows in a triangular duct are compared with previous published results, showing agreement with 0.13 % in Newtonian region and 2.85 % in power law region. These shear-thinning fluid results also showed the 12% increase of convective heat transfer enhancement compared with Newtonian heat transfer.

Steady Shear Flow Properties of Aqueous Poly(Ethylene Oxide) Solutions (폴리에틸렌옥사이드 수용액의 정상유동 특성)

  • Song, Ki-Won;Kim, Tae-Hoon;Chang, Gap-Shik;An, Seung-Kook;Lee, Jang-Oo;Lee, Chi-Ho
    • Journal of Pharmaceutical Investigation
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    • v.29 no.3
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    • pp.193-203
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    • 1999
  • In order to investigate systematically the steady shear flow properties of aqueous po1y(ethylene oxide) (PEO) solutions having various molecular weights and concentrations, the steady flow viscosity has been measured with a Rheometrics Fluids Spectrometer (RFS II) over a wide range of shear rates. The effects of shear rate, concentration, and molecular weight on the steady shear flow properties were reported in detail from the experimentally measured data, and then the results were interpreted using the concept of a material characteristic time. In addition, some flow models describing the non-Newtonian behavior (shear-thinning characteristics) of polymeric liquids were employed to make a quantitative evaluation of the steady flow behavior, and the applicability of these models was examined by calculating the various material parameters. Main results obtained from this study can be summarized as follows: (1) At low shear rates, aqueous PEO solutions show a Newtonian viscous behavior which is independent of shear rate. At shear rate region higher than a critical shear rate, however, they exhibit a shear-thinning behavior, demonstrating a decrease in steady flow viscosity with increasing shear rate. (2) As an increase in concentration and/or molecular weight, the zero-shear viscosity is increased while the Newtonian viscous region becomes narrower. Moreover, the critical shear rate at which the transition from the Newtonian to shear-thinning behavior occurs is decreased, and the shear-thinning nature becomes more remarkable. (3) Aqueous PEO solutions show a Newtonian viscous behavior at shear rate range lower than the inverse value of a characteristic time $1/{\lambda}_E$, while they exhibit a shear-thinning behavior at shear rate range higher than $1/{\lambda}_E$. For aqueous PEO solutions having a broad molecular weight distribution, the inverse value of a characteristic time is not quantitatively equivalent to the critical shear rate, but the power-law relationship holds between the two quantities. (4) The Cross, Carreau, and Carreau-Yasuda models are all applicable to describe the steady flow behavior of aqueous PEO solutions. Among these models, the Carreau-Yasuda model has the best validity.

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Comparison of shear rate and viscosity of the commercial dental impression materials (치과진료용 인상재의 전단율과 점도의 비교)

  • Jin, Myoung-Hoon;Lee, Kwang-Rae
    • Journal of Industrial Technology
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    • v.34
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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.

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Examination of Spread-Recoil Behavior of a Shear-thinning Liquid Drop on a Dry Wall (전단희석 액적의 건조 벽면 충돌 후 전개-수축 거동의 관찰)

  • An, Sang-Mo;Lee, Sang-Yong
    • Journal of ILASS-Korea
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    • v.14 no.3
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    • pp.131-138
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    • 2009
  • In the present study, spread-recoil behavior of a drop of shear-thinning liquid (xanthan solution) on a dry wall (polished stainless-steel plate) was examined and compared with that of Newtonian liquid (glycerin solution). Nine different kinds of xanthan and glycerin solutions were tested, including three pairs of xanthan and glycerin solutions, each having the same viscosity in low shear rate region ($10^{-2}-10^0\;l/s$). The drop behavior was visualized and recorded using a CCD camera. The maximum diameter and the spreading velocity of the xanthan drops turned out to be significantly larger and the time to reach their final shape was much shorter compared to the cases with the glycerin solutions, due to the smaller viscous dissipation resulted from lower viscosity in the higher shear rate region (>$10^0\;l/s$). As a result, the maximum diameters were measured to be larger than the predicted values based on the model proposed for Newtonian liquids, and the deviation was more pronounced with the solution with the larger viscosity variation. Consequently, viscosity variation with the shear rate was found to be a dominant factor governing the spread-recoil behavior of shear-thinning drops.

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Effects of Solvent Mixtures on Dispersion and Rheology of Alumina/zirconia Tape Casting Slurries (알루미나/지르코니아 테이프 케스팅 슬러리의 분산과 레올로지에 미치는 용매혼합의 영향)

  • Kim, Ji-Hyeon;Yang, Tae-Yeong;Lee, Yun-Bok;Yun, Seok-Yeong;Park, Heung-Chae
    • Korean Journal of Materials Research
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    • v.11 no.6
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    • pp.519-526
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    • 2001
  • The effects of methyl isobutyl ketone(MIBK)/ethanol(EtOH) solvent mixtures on the dispension, particle size distribution and rheology of $Al_2$O$_3$/ZrO$_2$ nonaqueous suspensions were investigated by measuring sedimentation density and viscosity. The sedimentation density of $Al_2$O$_3$ and ZrO$_2$ particles increased in MIBK-rich($\geq$60 vol%) solvents with 'Hypermer' KD-1 as a dispersant. The ball-milled suspensions in 80MIBK/20EtOH(vol%) solvent exhibited the narrow and unimodal particle size distribution. Although all Suspensions exhibited the Pseduo-Plastic flow(Shear thinning) the shear thinning behavior was somewhat different depending on the mixture ratio of $Al_2$O$_3$/ZrO$_2$ and MIBK/EtOH. Under a given shear rate( <300 s$^{-1}$ for $Al_2$O$_3$; <3000 s$^{-1}$ for ZrO$_2$) the strongest shear thinning appeared in the $Al_2$O$_3$ and ZrO$_2$ suspensions with pure MIBK solvent. The shear thinning was nearly independable on the mixture ratio of $Al_2$O$_3$/ZrO$_2$ in case of using the identical solvent(80MIBK/20EtOH, vol%).

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Shear Thinning Effects by VII Added Lubricant with In-Situ Optical Viscometer

  • Jang Siyoul
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.215-223
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    • 2003
  • Viscosity index improver (VII) is one of the major additives to the modern multigrade lubricants for the viscosity stability against temperature rise. However, it causes shear thinning effects which make the film thickness lessened very delicately at high shear rate $(over\;10^5\;s^{-1})$ of general EHL contact regime. In order to exactly verify the VII's performance of viscosity stability at such high shear rate, it is necessary to make the measurement of EHL film thickness down to $\~100nm$ with fine resolution for the preliminary study of viscosity control. In this work, EHL film thickness of VII added lubricant is measured with the resolution of $\~5nm$, which will give very informative design tool for the synthesis of lubricants regarding the matter of load carrying capacity at high shear rate condition.

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Comparison of Shear-Thinning Blood Flow Characteristics between Longitudinal and Transverse Vibration

  • Choi, Sung-Ho;Shin, Se-Hyun;Lee, Kyung-Tae
    • Journal of Mechanical Science and Technology
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    • v.18 no.12
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    • pp.2258-2264
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    • 2004
  • This article described the numerical investigation of shear-thinning blood flow characteristics when subjected to longitudinal and transverse vibrations and delineated the underlying mechanisms of the flow rate enhancements, respectively. In order to fully consider the mechanical vibrations of the capillary, a moving wall boundary condition was adopted. The present numerical results showed that the longitudinal vibration caused a significant increase of wall shear rates, which resulted in a decrease of viscosity and the subsequent increase of flow rates. However, the shear rate for the transverse vibration was slightly increased and the calculated flow rate was underestimated comparing with the previous experimental results.

Atomization of Shear-Thinning Liquid Slurry Discharging from Fan Spray Nozzles (고형성분이 포함된 전단희석 유체의 선형(扇形) 분무노즐을 통한 미립화)

  • An, S.M.;Ryu, S.U.;Lee, S.Y.
    • Journal of ILASS-Korea
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    • v.13 no.1
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    • pp.42-50
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    • 2008
  • In the present work, atomization characteristics of shear-thinning liquid slurry discharging from fan spray nozzles were studied experimentally for spray painting applications. The effects of solid particle size and concentration on the properties (especially on the viscosity) of suspensions and mean drop size were examined by using model fluids. In the range of low particle concentration (below 3 wt%), the fluid viscosity was primarily determined by the particle size. On the other hand, in the range of high particle concentration (higher than 10 wt%), the agglomeration phenomenon and the oil absorption capability of solid particles played major roles in determining the fluid viscosity. In the high concentration region, which most of the paints belong to, the fluid became more viscous and the shear thinning behavior appeared more prominent as the particle concentration was increased. In this region, mean drop size(SMD) decreased more rapidly with the increase of the injection pressure. Also, SMD became larger with the higher particle concentration and the larger particle size.

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