• Title/Summary/Keyword: fluid and flow

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Multiphase CFD Analysis of Microbubble Generator using Swirl Flow (선회유동을 이용한 마이크로버블 발생기의 다상유동 전산유체역학 해석)

  • Yun, S.I.;Kim, H.S.;Kim, J.K.
    • Journal of the Korean Society for Heat Treatment
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    • v.35 no.1
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    • pp.27-32
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    • 2022
  • Microbubble technology has been widely applied in various industrial fields. Recently, research on many types of microbubble application technology has been conducted experimentally, but there is a limit in deriving the optimal design and operating conditions. Therefore, if the computational fluid dynamics (CFD) analysis of multiphase flow is used to supplement these experimental studies, it is expected that the time and cost required for prototype production and evaluation tests will be minimized and optimal results will be derived. However, few studies have been conducted on multiphase flow CFD analysis to interpret fluid flow in microbubble generators using swirl flow. In this study, CFD simulation of multiphase flow was performed to analyze the air-water mixing process and fluid flow characteristics in a microbubble generator with a dual-chamber structure. Based on the simulation results, it was confirmed that a negative pressure was formed on the central axis of rotation due to the strong swirling flow. And it could be seen that the air inside the suction tube was introduced into the inner chamber of the microbubble generator. In addition, as the high-speed mixed fluid collided with external water sucked by the negative pressure near the outlet, a large amount of microbubbles was ejected due to the shear force between the two flows flowing in opposite directions.

Critical Fluid Velocity of Fluid-conveying Cantilevered Cylindrical Shells with Intermediate Support (중간 지지된 유체 유동 외팔형 원통셸의 임계유속)

  • Kim, Young-Wann
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.5
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    • pp.422-429
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    • 2011
  • The critical fluid velocity of cantilevered cylindrical shells subjected to internal fluid flow is investigated in this study. The fluid-structure interaction is considered in the analysis. The cantilevered cylindrical shell is supported intermediately at an arbitrary axial position. The intermediate support is simulated by two types of artificial springs: translational and rotational spring. It is assumed that the artificial springs are placed continuously and uniformly on the middle surface of an intermediate support along the circumferential direction. The steady flow of fluid is described by the classical potential flow theory. The motion of shell is represented by the first order shear deformation theory (FSDT) to account for rotary inertia and transverse shear strains. The effect of internal fluid can be considered by imposing a relation between the fluid pressure and the radial displacement of the structure at the interface. Numerical examples are presented and compared with existing results.

Numerical investigation of ceramic particle movement for injected gas flow rate in cyclone separator system (사이클론 분리기 시스템 내에서의 가스 주입 유속에 따른 세라믹 입자 거동 전산모사)

  • 우효상;심광보;정용재
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.13 no.3
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    • pp.145-151
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    • 2003
  • Using computational fluid dynamics (CFD) method, we investigated three-dimensional fluid flow field and particle movement with respect to the injected gas flow rate variation in typical cyclone separator system. The results of numerical investigation were deduced by coupling the analysis of fluid flow field with Wavier-stokes equation and the tracking of the particle trajectory with Langrangian approach. It was shown that the increasing of injected gas flow rate resulted in the increasing of pressure loss in the separator. This change of inner pressure had an effect on an aspect of the fluid flow in the separator. Particle movement was determined by fluid flow in the separator and was fully depended on a diameter of particles under the fixed flow rate. Increasing of injected gas flow rate was led to an increasing of the trace of particle, so the particles moved to the lower part of the separator. For this reason, the minimum diameters of the particles were decreased and increased the separation rate under the fixed particle diameter. In conclusion, the changes of injected gas flow rate have an important factor to the fluctuation of the fluid flow field and particle trajectory in the separator.

The visual Simulation of Fluid Flow with Free Surface in a Virtual Water Tank (가상수조에서 자유표면을 가진 유체흐름의 가시화시뮤레이션)

  • 김남형;김남국
    • Journal of Ocean Engineering and Technology
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    • v.14 no.3
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    • pp.35-40
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    • 2000
  • SMAC method is, one of the numerical simulation techniques, modified from the original MAC for the time-dependent variation of fluid flows. The Navier-Stokes equation for incompressible time-dependent viscous flow is applied and, also marker particles which move with the fluid are used. Two-dimensional numerical computations of fluid flow are carried out in a virtual water tank. This paper has shown very well the movements of marker particles using SMAC method.

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Nonlinear Characteristics of Flow Separation Induced Vibration at Low-Speed Using Coupled CSD and CFD technique (전산구조진동/전산유체 기법을 연계한 저속 유동박리 유발 비선형 진동특성 연구)

  • Kim, Dong-Hyun;Chang, Tae-Jin;Kwon, Hyuk-Jun;Lee, In
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.140-146
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    • 2002
  • The fluid induced vibration (FIV) phenomena of a 2-D.O.F airfoil system have been investigated in low Reynolds number incompressible flow region. Unsteady flows with viscosity are computed using two-dimensional incompressible Navier-stokes code. To validate developed Navier-Stokes code, steady and unsteady flow fields around airfoil are analyzed. The present fluid/structure interaction analysis is based on the most accurate computational approach with computational fluid dynamics (CSD) and computational structural dynamics (CSD) techniques. The highly nonlinear fluid/structure interaction phenomena due to severe flow separations have been analyzed fur the low Reynolds region (R$_{N}$ =500~5000) that has a dominancy of flow viscosity. The effect of R$_{N}$ on the fluid/structure coupled vibration instability of 2-DOF airfoil system is presented and the effect of initial angle of attack on the dynamic instability are also shown.own.

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A Study on Dehumidification Characteristics of Hollow Fiber Membrane Module for Pneumatic Power Unit Using Fluid-Solid Interaction Analysis (유동-구조 연성해석을 이용한 공압용 파워 유닛에 사용되는 중공사막 모듈에 대한 제습특성 연구)

  • Jeong, Eun-A;Khan, Haroon Ahmad;Lee, Kee-Yoon;Yun, So-Nam
    • Journal of Drive and Control
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    • v.16 no.4
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    • pp.65-73
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    • 2019
  • In this study, flow analysis and fluid-solid interaction analysis were conducted on a hollow fiber membrane module used for analysis of dehumidification characteristics. To ensure the reliability of the flow analysis results, the dehumidification experiment was performed under the temperature of 30℃ and relative humidity of 30% RH. The results of the dehumidification experiments were compared with the flow analysis results. The results of dehumidification experiments and flow analysis had a difference of approximately 5%. A 1-Way fluid-solid interaction analysis with various materials was conducted. From the results, it was found that the baffle with the largest shape deformation (polyethylene material) was subjected to 2-way fluid-solid interaction. The analysis of fluid flow and dehumidification characteristics were analyzed according to the shape deformation of the baffle.

Vibration and stability of embedded cylindrical shell conveying fluid mixed by nanoparticles subjected to harmonic temperature distribution

  • Shokravi, Maryam;Jalili, Nader
    • Wind and Structures
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    • v.25 no.4
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    • pp.381-395
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    • 2017
  • Nonlinear vibration and instability of cylindrical shell conveying fluid-nanoparticles mixture flow are studied in this article. The surrounding elastic medium is modeled by Pasternak foundation. Mixture rule is used for obtaining the effective viscosity and density of the fluid-nanoparticles mixture flow. The material properties of the elastic medium and cylindrical shell are assumed temperature-dependent. Employing first order shear deformation theory (FSDT), the motion equations are derived using energy method and Hamilton's principal. Differential quadrature method (DQM) is used for obtaining the frequency and critical fluid velocity. The effects of different parameters such as volume percent of nanoparticles, boundary conditions, geometrical parameters of cylindrical shell, temperature change, elastic foundation and fluid velocity are shown on the frequency and critical fluid velocity of the structure. Results show that with increasing volume percent of nanoparticles in the fluid, the frequency and critical fluid velocity will be increases.

Evaluation of the Effect on the Valve Flow Coefficient by Attached Fitting (밸브 후단 피팅에 따른 밸브 용량계수의 영향 평가)

  • Kang, Seung-Kyu;Lee, Won-Sik;Yoon, Joon-Yong;Min, Kyung-Wha
    • The KSFM Journal of Fluid Machinery
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    • v.6 no.4 s.21
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    • pp.29-37
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    • 2003
  • This study was undertaken to verify the effect of flow coefficient when a globe control valve was attached by different type of fitting. The valve flow coefficient is usually determined by measuring the flow rate and the pressure drop with the connection of straight pipe through the valve. The effect of different fitting that is mounted on the downstream of the valve is studied. Four types of fittings and three distances between the valve and a downstream fitting are compared parametrically to investigate the effect on the flow coefficient of it. Measured flow coefficient and numerically predicted value by using computational fluid dynamics were compared in detail. It is concluded that the flow coefficient is reduced if the fitting is attached after a valve, but the effect of different type of fitting is not crucial.

Effects of Fluid Velocity on Acoustic Transmission Loss of Simple Expansion Chamber (유동속도가 단순확장관 음향투과손실에 미치는 영향 해석)

  • Kwon, Jin;Jeong, Weui-Bong;Hong, Chin-Suk
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.10
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    • pp.994-1002
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    • 2012
  • Acoustic power transmission loss(TL) is an important performance of the muffler system. TL will be affected by the velocity of the fluid in duct since acoustic pressure varies according to the fluid velocity. In this paper, two kinds of fluid model, potential flow and turbulent flow, for the fluid flowing in simple expansion chamber are considered. The effects of their two fluid models in acoustic TL are investigated for the straight and L-shaped simple expansion chamber. In higher frequency range, the characteristics of TL of the two fluid models show different results. The variation of TL according to the fluid velocity is shown more distinctly when turbulence model is used. Turbulent flow model should be used to obtain better estimation of acoustic TL in higher frequency range.

Eulerian Two-Phase Flow Analysis for Solid-Liquid Mixing in a Industrial Mixer (산업용 교반기의 고체-액체 혼합에 대한 Eulerian Two-Phase 유동해석)

  • Song, Ae-Kyung;Hur, Nahm-Keon;Won, Chan-Shik;Ahn, Ick-Jin
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.471-474
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    • 2006
  • The Mixer is apparatus that help precipitation or an inhomogeneous distribution of various phases to be mixed and that user makes necessary material mixing one or the other. Mainly the mixer which is used from chemical and food industry is very important system in engineering that mixes the material. The inside flow of the mixer under the actual states which put a basis in flow of the fluid is formed rotation of the impeller. The inside flow of impeller will be caused by various reasons change with shape of impeller, number of rotation, mixing material and flow pattern of free surface etc. Also mixer study depended in single-phase flow and experimental research. So the numerical analysis of flow mixing solid-fluid particle is simulated. It is become known, that the case where agitator inside working fluid includes the solid particle the sinkage reverse which the solid particle has decreases an agitation efficiency. From the research which it sees the hazard solid which examines the effect where the change of the sinkage territory which it follows agitation number of revolution and diameter of the particle goes mad to an agitator inside flow distribution - numerical analysis the inside flow distribution of liquid state with Eulerian Two-Phase Method.

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