• Title, Summary, Keyword: immiscible fluids

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DIRECT NUMERICAL SIMULATION OF IMMISCIBLE GAS BUBBLE DISPLACEMENT IN 2D CHANNEL (2차원 관내 유동에서 불활성 기체 제거과정의 직접 수치 해석)

  • Shin, S.
    • Journal of computational fluids engineering
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    • v.12 no.3
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    • pp.41-46
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    • 2007
  • Dynamic behavior of immiscible gas bubble attached to the wall in channel flow plays very important role in many engineering applications. Special attention has been paid to micro direct methanol fuel cell(${\mu}$DMFC) where surface tension becomes dominant factor with minor gravitational effect due to its reduced size. Therefore, displacement of $CO_2$ bubble generating on a cathode side in ${\mu}$DMFC can be very difficult and efficient removal of $CO_2$ bubbles will affect the overall machine performance considerably. We have focused our efforts on studying the dynamic behavior of immiscible bubble attached to the one side of the wall on 2D rectangular channel subject to external shear flow. We used Level Contour Reconstruction Method(LCRM) which is the simplified version of front tracking method to track the bubble interface motion. Effects of Reynolds number, Weber number, advancing/receding contact angle and property ratio on bubble detachment characteristic has been numerically identified.

Numerical Study on The Pressure Drop of Immiscible Two-Phase Flow in The Pressure Driven Micro Channel Using Lattice Boltzmann Method (Lattice Boltzmann 방법을 이용한 압력구동 미세채널 내 비혼합 2상 유체 흐름의 압력강하에 대한 수치적 연구)

  • Jeong, Soo-In;Kim, Kui-Soon;Kang, Beom-Soon
    • 한국전산유체공학회:학술대회논문집
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    • pp.436-439
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    • 2008
  • Computer simulation of multiphase flows has grown dramatically in the last two decades. In this work, we have studied the flow characteristics of immiscible two fluids in a 2-D micro channel driven by pressure gradient using multi-phase lattice Boltzmann method suggested by Shan and Chen(1993) considering the fluid-surface interaction. we tried to examine the effects of parameters related to the two phase flow characteristics and pressure drop in the micro channel like contact angle and channel configuration by changing their value. The results of current study could show the lattice Boltzmann method can simulate the behaviors of two phase flow in the region of micro fluidics well.

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Coalescence behavior of dispersed domains in binary immiscible fluid mixtures having bimodal size distributions under steady shear flow

  • Takahashi Yoshiaki;Kato Tsuyoshi
    • Korea-Australia Rheology Journal
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    • v.17 no.3
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    • pp.125-130
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    • 2005
  • Coalescence process of binary immiscible fluid mixtures having bimodal size distributions, prepared by mixing two pre-sheared samples at different shear rates, ${\gamma}_{pre1}\;and\;{\gamma}_{pre2}$, under shear flow at a final shear rate, ${\gamma}_f$, are examined by transient shear stress measurements and microscopic observations in comparison with the results for simply pre-sheared samples having narrow size distributions (unimodal distribution samples). Component fluids are a silicone oil (PDMS) and a hydrocarbon-formaldehyde resin (Genelite) and their viscosities are 14.1 and 21.0 $pa{\cdot}sec$ at room temperature $(ca.\;20^{\circ}C)$, respectively. The weight ratio of PDMS: Genelite was 7:3. Three cases, $({\gamma}_{pre1}=7.2sec^{-1},\;{\gamma}_{pre2}=12.0sec^{-1}\;and\;{\gamma}_f=2.4sec^{-1}),\;({\gamma}_{pre1}=0.8sec^{-1},\;{\gamma}_{pre2}=4.0sec^{-1}\;and\;{\gamma}_f=2.4sec^{-1}),\;and\;({\gamma}_{pre1}=7.2sec^{-1},\;{\gamma}_{pre2}=12.0^sec^{-1}\;and\;{\gamma}_f=7.2sec^{-1})$ the first case, transient shear stress did not show any significant difference but domains larger than the initial state are observed at short times. In the latter cases, there exist undershoot of shear stress, reflecting existence of deformed large domains, which is confirmed by the direct observation. It is concluded that coalescence between large and small domains more frequently occur than coalescence between the domains with similar size in the bimodal distribution samples.

Recent Emulsion Technology in Cosmetics (화장품용 유화 제조기술 최근동향)

  • Hwang, So-Ra;Nam, Jin-Oh;Lee, Byung-Jin;Song, Woo-Ho;Lee, Chang-Soo
    • KSBB Journal
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    • v.27 no.4
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    • pp.207-214
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    • 2012
  • Emulsions are mixture of immiscible liquids in which one is dispersed in all over the other. They have been applied to many applications including cosmetics, foods, drug delivery system (DDS), fine chemicals, and chemical separations. Especially, emulsion technology is one of the most useful technique to formulate cosmetics such as eye cream, foundation, and foam cleansing. In general, the emulsions can be generated by mechanical agitation of two immiscible fluids. However, the emulsions obtained by conventional method have limited in stability, monodispersity, and complicate process. We describe here preparation techniques of representative cosmetic emulsions such as liposome, liquid crystal emulsion, nanoemulsion, multiple emulsion, and pickering emulsion. Furthermore, various factors which can control the physical properties of each cosmetic emulsions are briefly discussed.

An Advection Scheme for the Transport of Fractional Volume of an Incompressible Fluid (비압축성 유체의 체적비 수송에 대한 대류항 계산 기법)

  • Kwak Ho Sang;Kuwahara Kunio
    • Journal of computational fluids engineering
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    • v.3 no.1
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    • pp.1-10
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    • 1998
  • 서로 섞이지 않는 두 비압축성 유체의 유동을 해석하기 위하여 VOF 방법에 기초한 수치 기법을 개발하였다. 유체간의 계면형상의 거동은 유동장내의 유체의 점유체적비의 변화에 의해 묘사되는데 이를 지배하는 이동방정식을 풀기 위한 새로운 대류항 계산법을 고안하였다. 대류항은 유체계면의 방향에 따라 풍상법과 역풍상법의 적절한 조합을 취하여 계산하는데 여기에 대각방향의 상류효과를 포함시켜 시간에 대한 2차 정확도를 갖도록 하였다. 또한 이 방법을 유량보정수송(FCT)법과 결합시켜 해의 단조성을 보장하였다. 몇 가지 단순 문제에 대한 시험 결과 이 기법이 수치오차에 의한 계면형상의 변형과 파손을 감소시킴을 확인하였다.

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The Effect of Flow Rate on the Process of Immiscible Displacement in Porous Media (다공성 매체 내 비혼성 대체 과정에서 주입 유량이 거동 양상에 미치는 영향)

  • Park, Gyuryeong;Kim, Seon-ok;Lee, Minhee;Wang, Sookyun
    • Journal of Soil and Groundwater Environment
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    • v.23 no.1
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    • pp.1-13
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    • 2018
  • A series of experiments using transparent micromodels with an artificial pore network etched on glass plates was performed to investigate the effects of flow rate on the migration and distribution of resident wetting porewater (deionized water) and injecting non-wetting fluid (n-hexane). Multicolored images transformed from real RGB images were used to distinguish n-hexane from porewater and pore structure. Hexane flooding followed by immiscible displacement with porewater, migration through capillary fingering, preferential flow and bypassing were observed during injection experiments. The areal displacement efficiency increases as the injection of n-hexane continues until the equilibrium reaches. Experimental results showed that the areal displacement efficiency at equilibrium increases as the flow rate increases. Close observation reveals that preferential flowpaths through larger pore bodies and throats and clusters of entrapped porewater were frequently created at lower flow rate. At higher flow rate, randomly oriented forward and lateral flowpaths of n-hexane displaces more porewater at an efficiency close to stable displacement. It may resulted from that the pore pressure of n-hexane, at higher flow rate, increases fast enough to overcome capillary pressure acting on smaller pore throats as well larger ones. Experimental results in this study may provide fundamental information on migration and distribution of immiscible fluids in subsurface porous media.

FREE SURFACE WAVES OF A TWO-LAYER FLUID OVER A STEP

  • Choi, Jeong-Whan;Whang, Sung-Im
    • Communications of the Korean Mathematical Society
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    • v.15 no.1
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    • pp.173-181
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    • 2000
  • The objective of this paper is to study two dimensional steady gravitational waves on the interface between two immiscible, inviscid and incompressible fluids bounded above by a horizontal rigid boundary and below by a rigid step. A KdV equation for the first order perturbation in an asymptotic expansion can appear. However the coefficient of the KdV theory fails in that case. By a unified asymptotic method, we overcome this difficulty and derive a modified KdV equation with forcing. We find homogeneous steady solutions and present numerical solutions.

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Numerical Study of Ejected Droplet Formation in Two-Liquid System

  • Song, Mu-Seok;Shunji Homma;Haruhisa Honda
    • Journal of Ship and Ocean Technology
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    • v.7 no.4
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    • pp.32-40
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    • 2003
  • Numerical simulation code is developed to study the formation of liquid drops from a nozzle into another quiescent liquid. The Navier-Stokes equations for two immiscible, incompressible, Newtonian fluids are solved on a fixed, staggered grid of cylindrical axisymmetric coordinates. Interfacial motion is captured using a Front-Tracking Method. The time variation of interfacial shape simulated by the code is in excellent agreement with experiments. Simulation results show that the viscosity ratio affects the size of the satellite drops.

Numerical study on the relation between flow parameters and the focal point of fluidic lens (유체 렌즈의 초점과 유동 인자의 상관관계에 대한 수치해석)

  • Lahooti, Mohsen;Kim, Daegyoum
    • Journal of the Korean Society of Visualization
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    • v.17 no.2
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    • pp.90-95
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    • 2019
  • In the present work, the effect of flow parameters such as volume flow rate on focal point of fluidic micro lens is investigated numerically. ANSYS Fluent is used for simulations, and the flow parameters and number of simulations are determined using the space filling method of design of experiment (DOE). Having determined the location of interfaces between fluids inside the micro lens which acts as the lens curvature, a ray tracking simulation on each case is performed using COMSOL Multiphysics to determine the focal point for each lens. These data are then used to provide a relation between flow parameters and the focal point of the lens.