• Title, Summary, Keyword: non-Newtonian flow phenomena

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Pulsatile Flow Analyses of Newtonian Fluid and Non-Newtonian Pluid in Circular Tube (원관내 뉴턴유체와 비뉴턴유체의 맥동유동특성)

  • Cho, Min-Tae;Roh, Hyung-Woon;Suh, Sang-Ho;Kim, Jae-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.11
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    • pp.1585-1596
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    • 2002
  • The objectives of the present study are to numerically and experimentally investigate the steady and pulsatile flow phenomena in the circular tubes, to quantitatively compare the flow characteristics of Newtonian and non-Newtonian fluids, and to find meaningful hemodynamic information through the flow analysis in the human blood vessels. The particle image velocimetry is adopted to visualize the flow fields in the circular tube. and the results from the particle image velocimetry are used to validate the results of the numerical analysis. In order to investigate the blood flow phenomena in the circular tube. constitutive equations, which are suitable to describe the rheological properties of the non-Newtonian fluids. are determined, and the steady and pulsatile momentum equations are solved by the finite volume prediction. The velocity vectors of the steady and pulsatile flow in the circular tube obtained by the particle image velocimetry arc in good agreement with those by the numerical analysis. For the given mass flow rate. the axial velocity profiles of the Newtonian and the non-Newtonian fluids appear differently. The pulsatile flow phenomena of the Newtonian and the non-Newtonian fluids are quite different from those of the steady flow.

Non-Newtonian Rheological Properties of Poly(vinyl alcohol) hydrogel (Poly(vinyl alcohol) hydrogel의 비 뉴톤 유변학적인 성질)

  • Kim, Nam-Jeong
    • Elastomers and Composites
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    • v.44 no.3
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    • pp.323-328
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    • 2009
  • The rheological properties of complex materials such as polymer melts show complicated non-Newtonian flow phenomena when they are subjected to shear flow. These flow properties are controlled by the characteristics of flow units and the interactions among the flow segments. The non-Newtonian flow curves of poly(vinyl alcohol) hydrogel were obtained in various concentrations and temperatures by using a cone-plate rheometer. By applying non-Newtonian flow equation to the flow curves for PVA hydrogel samples, the rheological parameters were obtained. The PVA hydrogel samples are shear thinning under increasing shear rate modes which result in thixotropic behavior.

Numerical analysis of viscoelastic flows in a channel obstructed by an asymmetric array of obstacles

  • Kwon, Young-Don
    • Korea-Australia Rheology Journal
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    • v.18 no.3
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    • pp.161-167
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    • 2006
  • This study presents results on the numerical simulation of Newtonian and non-Newtonian flow in a channel obstructed by an asymmetric array of obstacles for clarifying the descriptive ability of current non-Newtonian constitutive equations. Jones and Walters (1989) have performed the corresponding experiment that clearly demonstrates the characteristic difference among the flow patterns of the various liquids. In order to appropriately account for flow properties, the Navier-Stokes, the Carreau viscous and the Leonov equations are employed for Newtonian, shear thinning and extension hardening liquids, respectively. Making use of the tensor-logarithmic formulation of the Leonov model in the computational scheme, we have obtained stable solutions up to relatively high Deborah numbers. The peculiar characteristics of the non-Newtonian liquids such as shear thinning and extension hardening seem to be properly illustrated by the flow modeling. In our opinion, the results show the possibility of current constitutive modeling to appropriately describe non-Newtonian flow phenomena at least qualitatively, even though the model parameters specified for the current computation do not precisely represent material characteristics.

The Non Newtonian Flow Mechanism and Rheological Properties of Polyurethane Melts (용융 폴리우레탄의 비 뉴톤 유동 메카니즘과 유변학적인 성질)

  • Kim, Nam-Jeong
    • Elastomers and Composites
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    • v.44 no.4
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    • pp.423-428
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    • 2009
  • The non-Newtonian flow curves of polyurethane melts were obtained by using a Physica cone-plate rheometer at various temperatures. The rheological parameters were obtained by applying non-Newtonian flow equation to the flow curves for polyurethane samples. When the polyurethane samples are under increasing-decreasing shear rate modes, the hysteresis loop and thixotropic behavior were shown. Polyurethane melts behave as strong gels when they are subjected to shear flow, but when the applied stress surpasses the yield stress, they exhibit non-linear viscoelasticity. Upon decreasing shear rate, its shear stress remains smaller than the values measured in the increasing shear rate mode, because of broken of its structure.

Flow Characteristics of Non-Newtonian Fluids in the Stenosed Branch Tubes (협착이 발생된 분기관내 비뉴턴유체의 유동특성 연구)

  • Suh, S.H.;Yoo, S.S.;Roh, H.W.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.8 no.3
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    • pp.307-316
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    • 1996
  • The objective of present study is to obtain information on the stenosis effects in the branch tubes for industrial piping system and atherogenesis processing in human arteries. Numerical solutions for flows of Newtonian and non-Newtonian fluids in the branch tubes are obtained by the finite volume method. Centerline velocity and pressure along the bifurcated tubes for water, blood and aqueous Separan AP-273 solution are computed and the numerical results of blood and the Separan solution are compared with those of water. Flow phenomena in the stenosed branch tubes are discussed extensively and predicted effectively. The effects of stenosis on the pressure loss coefficients are determined.

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Thixotropic Equation and Rheological Parameters on Non-Newtonian Flow Mechanism (비 뉴톤 유동 메카니즘에서 틱소트로피 식과 유변 파라메타)

  • Kim, Nam Jeong
    • Journal of the Korean Applied Science and Technology
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    • v.32 no.3
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    • pp.386-393
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    • 2015
  • The rheological properties of complex materials such as colloid dispersion show complicated non-Newtonian flow phenomena when they are subjected to shear flow. These flow properties are controlled by the characteristics of flow units and the interactions among the flow segments. The rheological parameters of relaxation time $({\beta}_2)_0$, structure factor $C_2$ and shear modulus $X_2/{\alpha}_2$ for various thixotropic flow curves was obtained by applying thixotropic equation to flow curves. The variations of rheological parameters are directly related to non-Newtonian flows, viscosities and activation energies of flow segments.

3-D Flow Analysis of Blood and Blood Substitutes in a Double Branching Model (이중 분지관내 혈액 및 혈액대용유체의 3차원 유동해석)

  • Suh, Sang-Ho;Yoo, Sang-Sin;Roh, Hyung-Woon
    • Journal of Biomedical Engineering Research
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    • v.18 no.2
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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

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NUMERICAL SIMULATION OF DEBRIS FLOW USING MULTIPHASE AND NON-NEWTONIAN FLUID MODEL (비선형 점성유체의 다상유동 모형을 이용한 토석류 전산해석)

  • Lee, S.;Hwnag, K.K.
    • Journal of computational fluids engineering
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    • v.22 no.1
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    • pp.95-102
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    • 2017
  • Debris flow is a composition of solid objects of various sizes, suspension and water, which occurs frequently as the results of landslide following heavy rainfall. This often causes extensive damage in the form of socio-economic losses and casualties as witnessed during the incident around Mt. Umyeon, Seoul in 2011. There have been numerous investigation to mitigate the impacts from debris flow; however, the estimation as preparedness measure has not been successful due to nonlinear and multiphase characteristics of phenomena both in material and process inherent in the debris flow. This study presents a numerical approach to simulate the debris flow using open source code of computational fluid dynamics, OpenFOAM with non-Newtonian viscosity model for three phase material modeling. In order to validate the proposed numerical method, the quantitative evaluations were made by comparisons with experimental results and qualitative analysis for the dispersion characteristics was carried for the case of debris flow in the actual incident from Mt. Umyeon.

Viscosity Measurement of Non-Newtonian Fluids Using the Transient Flow Phenomena in the Capillary Tube (모세관내 과도유동현상을 이용한 비뉴턴유체의 점도측정)

  • Cho, Min-Tae;Suh, Sang-Ho;Yoo, Sang-Sin
    • Proceedings of the KSME Conference
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    • pp.738-741
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    • 2001
  • The purpose of the present study is to measure the viscosity of liquid in the capillary tube viscometer using the unsteady flow concept. The capillary tube viscometer is consisted of a small cylindrical reservoir, capillary tubes, and the mass flow rate measuring system interfaced with computer. Two capillary tubes with 1.152 and 3.002 mm I.D. are used to determine the diameter effects on the viscosity measurements. The instantaneous shear rate and gravitational driving force in the capillary tube are determined by measuring the mass flow rate through the capillary tube instantaneously. The measured viscosities of water and aqueous Separan solution are in good agreement with the reported experimental data.

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Effect of Viscosity Variation on Flow Characteristic in Thixoforming Process of Semi-Solid Aluminium Alloys (반용융 알루미늄 합금의 Thixoforming 공정에서 점도의 변화가 유도특성에 미치는 영향)

  • 강충길;이유철
    • Transactions of Materials Processing
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    • v.8 no.2
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    • pp.188-199
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    • 1999
  • Semi-Solid Forming Process(Thixoforming, Rheocasting) is a novel forming process which has some advantages compared with conventional die casting, squeeze casting and hot/cold forging. In this study. Thixoforming process was selected as analysis processing in terms of billet handling and easiness of automation process. The Thixoforming process consists of reheating process of billet, billet handling, filling inot the die cavity and solidification of SSM part. In filling process, two rheology models which were Newtonian and Non-Nettonian model (Ostwald-deWaele)were verified with experimental results. The Ostwald-deWaele model shows the good agreement to the real flow and filling phenomena in die cavity. To give a boost the economical efficiency of Thixoforming process and to ensure the good forming result, reheating device coupled die set was proposed and the initial billet temperature for system that was found from experimental resluts. This study presents an overview of application of numerical analysis for simulation of semi-solid metal forming process to reduce the lead time for development of manufacturing part in industrial field.

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