• Title/Summary/Keyword: Viscosity Effect

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Effect of nonionic surfactants on the electrorheology of emulsions

  • Ha, Jong-Wook;Moon, Jung-Hyuk;Yang, Seung-Man
    • Korea-Australia Rheology Journal
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    • v.11 no.3
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    • pp.241-246
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    • 1999
  • In this study, we consider the effect of nonionic surfactants on the rheological responses of emulsion systems under the action of a uniform do electric field. The model emulsions consist of a less conducting dispersed phase and a more conducting continuous phase. When the shear flow is weak, the positive viscosity effect is produced due to the formation of chain-like morphology. The nonionic surfactants used here generate two distinctively different effects. Specifically, first, the steric hindrance induced by the surfactant molecules renders the structure unstable, and thereby reduces the degree of positive viscosity effect. Secondly, the presence of surfactant molecules also prevents the rotation of the dispersed droplets by anchoring across the interface or by decreasing the size of dispersed phase. The second effect suppresses the negative viscosity effect.

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Numerical calculations of characteristics of Argon arc plasma using the control volume method (제어체적법에 의한 Ar 아크 플라즈마의 특성 계산)

  • Kim, Oe-Dong;Ko, Kwang-Cheol;Kang, Hyung-Boo
    • Proceedings of the KIEE Conference
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    • pp.1404-1406
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    • 1995
  • In this paper, argon gas was used for numerical analysis of an arc in a cutting plasma torch driven by constant current. We established nozzle-constricting type torch domain and calculated steady state characteristics of argon arc plasma using the control volume method(CVM). For simplicity, we assumed that the flow field is laminar and the local thermodynamic equilibrium(LTE) prevails in all domain regions. We also neglected cathode-fall and anode-fall effects. Considering magnetic pinch effect and viscosity effect, we solved the momentum equation. Voltage drop in the arc column due to input current was calculated from the temperature field obtained by the energy balance equation.

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Molecular Conformation and Non-Newtonian Viscosity Behavior of Poly(L-proline) in Various Solvent Systems

  • Jang, Chun-Hag;Kim, Hyun-Don;Lee, Jang-Oo
    • Bulletin of the Korean Chemical Society
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    • v.15 no.5
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    • pp.399-404
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    • 1994
  • The non-Newtonian viscosities (the specific or intrinsic viscosities) of poly(L-proline) (PLP, $M_v$=19,000 and 32,000) in various mixed-solvent systems like water-propanol and acetic acid-propanol of varying compositions were measured during the reverse mutarotation (Form II ${\rightarrow}$Form I) by the application of external pressure (up to 4.5 psi). The non-Newtonian viscosity effect was found to be larger in acetic acid-propanol system than in water-propanol system and to somewhat decrease during the reverse mutarotation at a given solvent system. The non-Newtonian viscosity behavior of PLP in aqueous salt ($CaCl_2$) solution was also studied, from which it was found that the degree of the non-Newtonian effect decreased with increasing salt concentration, and increased with increasing PLP molecular weight. These findings could be explained in terms of conformational changes of PLP in solution (like the helix-helix or helix-coil transition) involved.

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Numerical Simulation and Analysis for Optimum Design of a Thermoacoustic Refrigerator (공명관식 열음향 냉동기의 최적설계를 위한 수치모사 및 설계인자 분석)

  • Kim, D.H.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.7 no.2
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    • pp.329-340
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    • 1995
  • Basic refrigeration effect and efficiency of a thermoacoustic refrigerator is studied. The refrigerator model for numerical simulation is composed of half wavelength resonator and appropriate stack of plate. Theoretical model for thermoacoustic refrigeration suggested by Swift et. al is adapted for numerical calculation. The model contains arbitrary viscosity effect of the gas filled in the resonator. The wave equation is integrated by using 4-th order Runge-Kutta algorithm to give pressure distribution along the stack of plate. Heat flux and COP are also calculated based on the energy flux equation. By analyzing the numerical simulation results, optimum values of design parameters for thermoacoustic refrigerator are obtained.

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Design of a New Dispensing System Featuring Piezoelectric Actuator (압전 작동기를 이용한 새로운 디스펜싱 시스템 설계)

  • Hung, Nguyen Quoc;Choi, Min-Kyu;Yoon, Bo-Young;Choi, Seung-Bok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.821-826
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    • 2006
  • This paper presents a novel type of hybrid dispensing head for IC fabrication and surface mount technology. The proposed mechanism consists of solenoid valve and piezoelectric stack as actuators, and provides positive-displacement and jet dispensing. The positive-displacement dispensing can produce desired adhesive amount without viscosity effect, while the jet dispensing can produce high precision adhesive amount. In order to determine the relationship between required voltage of the piezo actuator and needle displacement, both static and dynamic analysis are undertaken, In addition, finite element analysis is performed in order to find optimal design parameters. Dispensing flow rate and pressure in the chamber are evaluated through fluid dynamic model.

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Effect of Matrix Viscosity on Clay Dispersion in Preparation of Polymer/Organoclay Nanocomposites

  • Ko, Moon-Bae;Jho, Jae-Young;Jo, Won-Ho;Lee, Moo-Sung
    • Fibers and Polymers
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    • v.3 no.3
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    • pp.103-108
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    • 2002
  • The viscosity effect of matrix polymer on melt exfoliation behavior of an organoclay in poly($\varepsilon$-caprolactone) (PCL) was investigated. The viscosity of matrix polymer was controlled by changing the molecular weight of poly($\varepsilon$-eaprolactone), the processing temperature, and the rotor speed of a mini-molder. Applied shear stress facilitates the diffusion of polymer chains into the gallery of silicate layers by breaking silicate agglomerates down into smaller primary particles. When the viscosity of PCL is lower, silicate agglomerates are not perfectly broken into smaller primary particles. At higher viscosity, all of silicate agglomerates are broken down into primary particles, and finally into smaller nano-scale building blocks. It was also found that the degree of exfoliation of silicate layers is dependent upon not only the viscosity of matrix but thermodynamic variables.

The Effect of Viscosity on the Spray Characteristics of Pressure Swirl Atomizer (스월분무특성에 미치는 점성의 영향)

  • Yoon, S.J.;Cho, D.J.
    • Journal of ILASS-Korea
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    • v.4 no.4
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    • pp.24-29
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    • 1999
  • In the pressure swirl atomizer, the liquid is injected through tangential passages into a swirl chamber, from which it emerges with both tangential and axial velocity components to form a thin conical sheet at the nozzle exit. This sheet rapidly attenuates, finally disintegrating into ligaments and then drops. The purpose of this study is to measure the spray characteristics according to variation of viscosity of the spray produced by the pressure swirl atomizer. The nozzle tested here were especially designed for this investigation. The discharge coefficient is determined by measuring the volume flow rate with a flow meter and the cone angle of the liquid sheets issuing from the nozzle is obtained from series of photographs of the sheet for various liquid viscosity and injection pressure. And mean drop size is measured by image processing method. It is found that the geometrical characteristics of the nozzle and the variation of viscosity were the influential parameters to determine the spray characteristics such as the cone angle, discharge coefficients and SMD.

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Design Optimization of Transonic Airfoils Based on the Navier-Stokes Equation (Navier-Stokes 방정식을 이용한 천음속 익형의 설계최적화 연구)

  • Lee Hyeong Min;Jo Chang Yeol
    • 한국전산유체공학회:학술대회논문집
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    • pp.177-185
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    • 1999
  • The airfoil design optimization procedures based on the Navier-Stokes equations were developed, This procedure enables more realistic and practical transonic airfoil designs. The modified Hicks-Henne functions were used to generate the shape of airfoils. Five Hick-Henne functions were used to design upper surface of airfoil only. To enhance the ability of Hick-Henne function to generate various airfoil shape with limited number of functions, the positions of control points were adjusted through optimization procedure. The design procedure was applied to the single-point design for the drag minimization problem with lift and area constraints. The result shows the capability of the procedure to generate much realistic airfoils with very small drag-creep in the low transonic regime. This is mainly due to the viscosity effect of Navier-Stokes flow analysis. However, in the higher transonic range tile drag-creep appears. The multi-point design is shown to be an effective way to avoid the drag-creep and improve off-design performance which is very similar in the Euler design.

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Simulation of free falling rigid body into water by a stabilized incompressible SPH method

  • Aly, Abdelraheem M.;Asai, Mitsuteru;Sonoda, Yoshimi
    • Ocean Systems Engineering
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    • v.1 no.3
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    • pp.207-222
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    • 2011
  • A stabilized incompressible smoothed particles hydrodynamics (ISPH) method is utilized to simulate free falling rigid body into water domain. Both of rigid body and fluid domain are modeled by SPH formulation. The proposed source term in the pressure Poisson equation contains two terms; divergence of velocity and density invariance. The density invariance term is multiplied by a relaxed parameter for stabilization. In addition, large eddy simulation with Smagorinsky model has been introduced to include the eddy viscosity effect. The improved method is applied to simulate both of free falling vessels with different materials and water entry-exit of horizontal circular cylinder. The applicability and efficiency of improved method is tested by the comparisons with reference experimental results.

Effect of Fluid Viscosity on the Suspension of a Single Particle in Channel Flow (채널 유동에서 점성이 단일 입자 혼합 유동의 suspension에 미치는 영향)

  • Choi, Hyoung-Gwon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.3
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    • pp.194-200
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    • 2009
  • Suspension of a single solid particle in a channel flow with a constant pressure gradient is studied numerically. The interaction of a circular particle with a surrounding Newtonian fluid is formulated using a combined formulation. Numerical results are presented using two dimensionless variables: the sedimentation Reynolds number and the generalized Froude number. From the present results, it has been shown that a solid particle is suspended at a smaller generalized Froude number as the viscosity of the surrounding fluid increases. The time taken for equilibrium position is found to be smaller as fluid viscosity increases when both : the sedimentation Reynolds number and the generalized Froude number are the same while, at the same situation, the dimensionless time taken for equilibrium position is to be nearly the same regardless of fluid viscosity when a dimensionless time variable is introduced