• Title/Summary/Keyword: Continuous Fluid

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Visualization of Flow Characteristics on Thermosyphon with Immiscible Binary Working Fluid (비 혼합 2유체 열사이폰의 유동 특성에 관한 가시적 연구)

  • Do, Sun Yub;Kang, Hawn Kook;Park, Seung Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.5
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    • pp.3022-3029
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    • 2015
  • This study presents experiments to visualize the internal flow and heat transfer characteristics of thermosyphon with immiscible of water-FC40 adopted as binary working fluid. Three different regimes depending on the amount of heat flux applied to the thermosyphon were observed: natural convection, pulse boiling, and continuous boiling. Boiling incipience took place in water, which has lower vapor pressure than FC40. During natural convection water was vaporized in liquid pool while liquid film flows were formed. On the other hand, meanwhile bubbles were generated in the liquid pool during pulse and continuous boiling, the binary working fluid of water-FC40 was observed as the mixture throughout a whole range of the thermosyphon.

Experimental Investigation of Flow Oscillations in a Semi-closed Two-phase Natural Circulation Loop (준밀폐형 2상자연순환 회로 내에서의 유동 진동에 관한 실험적 연구)

  • Kim, Jong Moon;Lee, Sang Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.12
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    • pp.1763-1773
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    • 1998
  • In the present experimental study, the flow behavior in a semi-closed two-phase natural circulation loop was examined. Water was used as the working fluid. Heat flux, heater-inlet subcooling, and flow restrictions at the heater-inlet and at the expansion-tank-line were taken as the controlling parameters Six circulation modes were identified by changing heat flux and inlet subcooling conditions ; single-phase continuous circulation, periodic circulation (A), two-phase continuous circulation, and periodic circulations (B), (C), and (D). Among these, the single-phase and two-phase continuous-circulation modes exhibit no significant oscillations and are considered to be stable. Periodic circulation (A) is characterized by the large amplitude two-phase f10w oscillations with the temporal single-phase circulation between them, while periodic circulation (B) featured by the flow oscillations with continuous boiling inside the heater section. Periodic circulation (C) appears to be the manometric oscillation with continuous boiling. Periodic circulation (D) has the longer period than periodic circulation (B) and a substantial amount of liquid flow back and forth through the expansion-tank-line periodically ; this mode is considered the pressure drop oscillation. Parametric study shows that the increases of the inlet- and expansion-tank-line- restrictions and the decrease of inlet subcooling broaden the range of the stable two-phase(continuous circulation) mode.

Fluid-Oscillation Coupled Analysis for HAWT Rotor Blade (One Degree of Freedom Weak Coupling Analysis with Hinge-Spring Model)

  • Imamura, Hiroshi;Hasegawa, Yutaka;Murata, Junsuke;Chihara, Sho;Takezaki, Daisuke;Kamiya, Naotsugu
    • International Journal of Fluid Machinery and Systems
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    • v.2 no.3
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    • pp.197-205
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    • 2009
  • Since large-scale commercial wind turbine generator systems such as MW-class wind turbines are becoming widely operated, the vibration and distortion of the blade are becoming larger and larger. Therefore the soft structure design instead of the solid-design is one of the important concepts to reduce the structural load and the cost of the wind turbine rotors. The objectives of the study are development of the fluid-structure coupled analysis code and evaluation of soft rotor-blade design to reduce the unsteady structural blade load. In this paper, fluid-structure coupled analysis for the HAWT rotor blade is performed by free wake panel method coupled with hinge-spring blade model for the flapwise blade motion. In the model, the continuous deflection of the rotor blade is represented by flapping angle of the hinge with one degree of freedom. The calculation results are evaluated by comparison with the database of the NREL unsteady aerodynamic experiment. In the analysis the unsteady flapwise moments in yawed inflow conditions are compared for the blades with different flapwise eigen frequencies.

Dynamics of the oscillating moving load acting on the hydroelastic system consisting of the elastic plate, compressible viscous fluid and rigid wall

  • Akbarov, Surkay D.;Ismailov, Meftun I.
    • Structural Engineering and Mechanics
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    • v.59 no.3
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    • pp.403-430
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    • 2016
  • This paper studies the dynamics of the lineal-located time-harmonic moving-with-constant-velocity load which acts on the hydro-elastic system consisting of the elastic plate, compressible viscous fluid - strip and rigid wall. The plane-strain state in the plate is considered and its motion is described by employing the exact equations of elastodynamics but the plane-parallel flow of the fluid is described by the linearized Navier-Stokes equations. It is assumed that the velocity and force vectors of the constituents are continuous on the contact plane between the plate and fluid, and impermeability conditions on the rigid wall are satisfied. Numerical results on the velocity and stress distributions on the interface plane are presented and discussed and the focus is on the influence of the effect caused by the interaction between oscillation and moving of the external load. During these discussions, the corresponding earlier results by the authors are used which were obtained in the cases where, on the system under consideration, only the oscillating or moving load acts. In particular, it is established that the magnitude of the aforementioned interaction depends significantly on the vibration phase of the system.

An enhanced incompressible SPH method for simulation of fluid flow interactions with saturated/unsaturated porous media of variable porosity

  • Shimizu, Yuma;Khayyer, Abbas;Gotoh, Hitoshi
    • Ocean Systems Engineering
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    • v.12 no.1
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    • pp.63-86
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    • 2022
  • A refined projection-based purely Lagrangian meshfree method is presented towards reliable numerical analysis of fluid flow interactions with saturated/unsaturated porous media of uniform/spatially-varying porosities. The governing equations are reformulated on the basis of two-phase mixture theory with incorporation of volume fraction. These principal equations of mixture are discretized in the context of Incompressible SPH (Smoothed Particle Hydrodynamics) method. Associated with the consideration of governing equations of mixture, a new term arises in the source term of PPE (Poisson Pressure Equation), resulting in modified source term. The linear and nonlinear force terms are included in momentum equation to represent the resistance from porous media. Volume increase of fluid particles are taken into consideration on account of the presence of porous media, and hence multi-resolution ISPH framework is also incorporated. The stability and accuracy of the proposed method are thoroughly examined by reproducing several numerical examples including the interactions between fluid flow and saturated/unsaturated porous media of uniform/spatially-varying porosities. The method shows continuous pressure field, smooth variations of particle volumes and regular distributions of particles at the interface between fluid and porous media.

A Study on the Fluid Flew with Ultrasonic Forcing by PIV Measurement (초음파가 가진된 유체유동의 PIV계측에 의한 연구)

  • 주은선;이영호;나우정;정진도
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.6
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    • pp.1281-1290
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    • 2001
  • A study on the fluid flow with ultrasonic forcing is carried out to obtain data for the turbulence enhancement. A large water tank is made of the transparent acrylic plates and a horizontal flow field is given by setting two acrylic tubes to face mutually on a horizontal line. A 2-dimensional PlV system which is composed of a continuous-output 4W Argon-ion laser, a high-speed video camera, a PC based by an image grabber and a high resolution monitor is used to investigate characteristics of the complex turbulence flow field. And a 2MHz ultrasonic transducer is used fur ultrasonic vibration forcing. Some experiments are carried out at Reynolds numbers of 2,000 and 4,000 and at 7 angles of ultrasonic incidence. In results, the flew velocity vector distribution, kinetic energy and turbulence intensity in both cases of with and without ultrasonic forcing are examined, compared and discussed by using PIV measurement. It is clarified that the ultrasonic forcing into flow field is valid to obtain the turbulence enhancement.

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The Present Status of Pumps Installed in the Large Merchant Ships (대형 상선에서의 펌프사용 현황)

  • Kim, You-Taek;Nam, Chung-Do;Lee, Young-Ho
    • The KSFM Journal of Fluid Machinery
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    • v.4 no.4 s.13
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    • pp.43-52
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    • 2001
  • Pumps arre used extensively for transporting fluid in many ships. However, the present state of pumps used in the large merchant ships has not been studied. In this paper, we have reported the general description of the operating pumps according to the different ship types(Bulk, Container, Car-Carrier, Tanker, LNG). Moreover, the pump total powers are compared with the main engine Normal Continuous Rating power and the pump total weights are also compared with the ship deadweight.

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TWO-DIMENSIONAL SHOCK WAVE DIFFREACTION IN DROPPET-LADEN GAS MEDIA (액적을 동반한 기체에서 이차원 충격파 회절)

  • Yeom, G.S.;Chang, K.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.362-364
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    • 2010
  • Shock wave interaction with droplet-gas medium is investigated in this paper. In the present computation, the shock wave is initially started in a pure gas and reflected from the wedge to interact with the droplet-ridden gas flows. We used the compressible two-fluid two-phase model that is solved by the two-fluid version of the HLL scheme. The interfacial drag force and heat transfer were included to model the interaction between continuous and dispersed phases. The parametric effect of void fraction on the shock wave reflection in the two-phase media was investigated.

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Investigation on fluid-particle velocity double correlation in fluid- particle two-phase turbulent flows (유체에 입자가 부상된 2상난류운동에서 유체-입자속도 2차상관관계에 관한 연구)

  • 양선규;최영돈
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.6
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    • pp.1438-1449
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    • 1988
  • An analysis of radiative heat transfer has been conducted on axisymmetric finite cylindrical media. It is assumed that the temperature in the media is uniformly distributed and the boundaries are diffusely emitting and reflecting at a constant temperature. The scattering phase function is represented by the delta-Eddington approximation to account for highly forward scattering by particulates just as in the combustion system. Exact numerical solutions are obtained by Gaussian quadrature method and compared with P-1 and P-3 approximation solutions to verify their engineering application limit. The effects of optical thickness, scattering albedo, wall emissivity and aspect ratio are investigated. The results show that P-3 approximation is found to be in good agreement with the exact solution.

Two-fluid modelling for poly-disperse bubbly flows in vertical pipes: Analysis of the impact of geometrical parameters and heat transfer

  • Andrea Allio ;Antonio Buffo ;Daniele Marchisio;Laura Savoldi
    • Nuclear Engineering and Technology
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    • v.55 no.3
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    • pp.1152-1166
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    • 2023
  • The bubbly flow of air or steam in subcooled water are investigated here in several test cases, characterized by different pipe sizes, bubble dimensions and flow rates, by means of CFD using a Eulerian-Eulerian approach. The performance of models that differ for the turbulence closure in the continuous phase, as well as for the description of the lift force on the dispersed phase, are compared in detail. When air is considered, the space of the experimental parameters leading to a reasonable performance for the selected models are identified and discussed, while the issues left in the modelling of the concurrent condensation are highlighted for the cases where steam is used.