• 제목/요약/키워드: turbulence and fluid dynamics

검색결과 376건 처리시간 0.021초

CFD 모델링을 이용한 화학공장의 안전거리 산정 방법론에 관한 연구 (A Methodology for Determination of the Safety Distance in Chemical Plants using CFD Modeling)

  • 백주홍;이향직;장창봉
    • 한국안전학회지
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    • 제31권3호
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    • pp.162-167
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    • 2016
  • As the simple empirical and phenomenological model applied to the analysis of leakage and explosion of chemical substances does not regard numerous variables, such as positional density of installations and equipment, turbulence, atmospheric conditions, obstacles, and wind effects, there is a significant gap between actual accident consequence and computation. Therefore, the risk management of a chemical plant based on such a computation surely has low reliability. Since a process plant is required to have outcomes more similar to the actual outcomes to secure highly reliable safety, this study was designed to apply the CFD (computational fluid dynamics) simulation technique to analyze a virtual prediction under numerous variables of leakages and explosions very similarly to reality, in order to review the computation technique of the practical safety distance at a process plant.

Conceptual design and numerical simulations of a vertical axis water turbine used for underwater mooring platforms

  • Wenlong, Tian;Baowei, Song;Zhaoyong, Mao
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제5권4호
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    • pp.625-634
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    • 2013
  • Energy is a direct restriction to the working life of an underwater mooring platform (UMP). In this paper, a vertical axis water turbine (VAWT) is designed to supply energy for UMPs. The VAWT has several controlled blades, which can be opened or closed by inside plunger pumps. Two-dimensional transient numerical studies are presented to determine the operating performance and power output of the turbine under low ocean current velocity. A standard k-${\varepsilon}$ turbulence model is used to perform the transient simulations. The influence of structural parameters, including foil section profile, foil chord length and rotor diameter, on the turbine performance are investigated over a range of tip-speed-ratios (TSRs). It was found that turbine with three unit length NACA0015 foils generated a maximum averaged coefficient of power, 0.1, at TSR = 2.

바닥취출 및 흡입시스템 공조방식에서 취출조건 변경시 실내공기환경 평가 (Evaluation of Indoor Air Environment by Changing Diffuser Location and Air Temperature with Under Floor Air Conditioning System)

  • 김세환;박종일
    • 설비공학논문집
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    • 제17권5호
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    • pp.397-403
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    • 2005
  • The thermal comfort of occupants is directly related to several environmental factors such as velocity of air flow, turbulence intensity and temperature distribution of indoor air. The purpose of this study is to evaluate the indoor air flow and temperature distribution in office area using under-floor air-conditioning system (UFAC System) based on the results from physical measurements and to perform a Computer Fluid Dynamics (CFD) under the same condition of inlet and outlet as field measurement. The results from the CFD simulation are similar to those from the field measurement. The results show that UFAC system is provide proper indoor condition for occupants.

CFD와 PIV test를 통한 원형 2차침전지 유입 및 유출배플 형상 최적화 (Optimization of influent and effluent baffle configuration of circular secondary clarifier using CFD and PIV test)

  • 최영균;배강형
    • 상하수도학회지
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    • 제28권1호
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    • pp.73-81
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    • 2014
  • One-dimensional flux theory (1DFT) is conventionally used for design of secondary clarifier of wastewater treatment plant. However, the 1DFT cannot describe turbulence, density current, shape parameters of the clarifier. In this study, we optimized the configurations of influent guide baffle and effluent baffle through the simulation using computational fluid dynamics (CFD) and its verification by particle image velocity (PIV) test. The energy dissipating inlet (EDI) without influent guide baffle ($0^{\circ}$) showed the best efficiency for minimizing downward velocity under the center well of the clarifier. The lowest velocity distribution around the effluent weir region could be obtained with the McKinney baffle (EB-2). The performances of the influent and effluent baffles were clearly verified by PIV test results.

An estimation of static aerodynamic forces of box girders using computational fluid dynamics

  • Watanabe, Shigeru;Inoue, Hiroo;Fumoto, Koichiro
    • Wind and Structures
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    • 제7권1호
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    • pp.29-40
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    • 2004
  • This study has focused on aerodynamics for a wind-resistance design about the single and tandem box girder sections to realize a super-long span bridge in the near future. Three-dimensional static analysis of flows around the fundamental single and tandem box girder sections with fairing is carried out by means of the IBTD/FS finite element technique with LES turbulence model. As the results of the analysis, computations have verified aerodynamic characteristics of both sections by the histories of aerodynamic forces, the separation and reattachment flow patterns and the surface pressure distributions. The relationship between the section shapes and the aerodynamic characteristics is also investigated in both sections. And the mechanism about the generation of fluctuating aerodynamic forces is discussed.

CFD-FEA ANALYSIS OF HYDRAULIC SHOCK ABSORBER VALVE BEHAVIOR

  • Shams, M.;Ebrahimi, R.;Raoufi, A.;Jafari, B.J.
    • International Journal of Automotive Technology
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    • 제8권5호
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    • pp.615-622
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    • 2007
  • In this study, a Coupled Computational Fluid Dynamics(CFD) and Finite Element Analysis(FEA) method are used to predict and evaluate the performance of an automotive shock absorber. Averaged Navier-Stokes equations are solved by the SIMPLE method and the RNG $k-\varepsilon$ is used to model turbulence. CFD analysis is carried out for different intake valve deflections and piston velocities. The force exerted on the valve in each valve deflection is obtained. The valve deflection-force relationship is investigated by the FEA method. The force exerted on the valve in each piston velocity is obtained with a combination of CFD and FEA results. Numerical results are compared with the experimental data and have shown agreement. Dependence of valve deflection as a function of piston velocity is investigated. Effects of hydraulic oil temperature change on valve behavior are also studied.

Numerical Visualization of Fluid Flow and Filtration Efficiency in Centrifugal Oil Purifier

  • Jung, Ho-Yun;Choi, Yoon-Hwan;Lee, Yeon-Won;Doh, Deog-Hee
    • Journal of Advanced Marine Engineering and Technology
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    • 제34권1호
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    • pp.84-91
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    • 2010
  • The centrifugal oil purifier is used in ships for purifying the engine lubrication oil. The momentum needed for the rotation of the cylindrical chamber is obtained by jet injections. The dust particles in the oil are separated by the centrifugal forces moving to the inner wall of the rotating cylindrical chamber body. The dust particles are eliminated when the particles are adsorbed onto the surface of the inner wall of the chamber body. The flow characteristics and the physical behaviours of particles in this centrifugal oil purifier have been investigated numerically and the filtration efficiencies have been evaluated. For the calculations, a commercial code has been used and the SST k-${\omega}$ turbulence model has been adopted. The MRF (Multiple Reference Frame) method has been introduced to consider the rotating effect of the flows. Under various variables, such as particle size, particle density and rotating speed, the filtration efficiencies have been evaluated. It has been verified that the filtration efficiency is increased with the increments of the particle size, the particle density and the rotating speed of the cylindrical chamber.

Numerical simulation of air discharged in subcooled water pool

  • Y. Cordova ;D. Blanco ;Y. Rivera;C. Berna ;J.L. Munoz-Cobo ;A. Escriva
    • Nuclear Engineering and Technology
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    • 제55권10호
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    • pp.3754-3767
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    • 2023
  • Turbulent jet discharges in subcooled water pools are essential for safety systems in nuclear power plants, specifically in the pressure suppression pool of boiling water reactors and In-containment Refueling Water Storage Tank of advanced pressurized water reactors. The gas and liquid flow in these systems is investigated using multiphase flow analysis. This field has been extensively examined using a combination of experiments, theoretical models, and Computational Fluid Dynamics (CFD) simulations. ANSYS CFX offers two approaches to model multiphase flow behavior. The non-homogeneous Eulerian-Eulerian Model has been used in this work; it computes global information and is more convenient to study interpenetrated fluids. This study utilized the Large Eddy Simulation Model as the turbulence model, as it is better suited for non-stationary and buoyant flows. The CFD results of this study were validated with experimental data and theoretical results previously obtained. The figures of merit dimensionless penetration length and the dimensionless buoyancy length show good agreement with the experimental measurements. Correlations for these variables were obtained as a function of dimensionless numbers to give generality using only initial boundary conditions. CFD numerical model developed in this research has the capability to simulate the behavior of non-condensable gases discharged in water.

Experimental and numerical aerodynamic investigation of a prototype vehicle

  • Akansu, Selahaddin Orhan;Akansu, Yahya Erkan;Dagdevir, Toygun;Daldaban, Ferhat;Yavas, Feridun
    • Wind and Structures
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    • 제20권6호
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    • pp.811-827
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    • 2015
  • This study presents experimental and numerical aerodynamic investigation of a prototype vehicle. Aerodynamics forces examined which exerted on a prototype. This experimental study was implemented in a wind tunnel for the Reynolds number between $10^5-3.1{\times}10^5$. Numerical aerodynamic analysis of the vehicle is conducted for different Reynolds number by using FLUENT CFD software, with the k-$\varepsilon$ realizable turbulence model. The studied model aims at verifying the aerodynamic forces between experimental and numerical results. After the Reynolds number of $2.8{\times}10^5$, the drag coefficient obtained experimentally becomes independent of Reynolds number and has a value of 0.25.

플라스틱 판형 열교환기의 와류발생기에 관한 연구 (A Study on the Vortex Generators of Plastic Plate Heat Exchangers)

  • 오윤영;유성연;고성호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2002년도 학술대회지
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    • pp.107-110
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    • 2002
  • The present study deals with CFD analysis of 'The vortex generators on plastic plate heat exchanger'. When a vortex generator is placed on the heat transfer surface, the flow gets more complex because it entails complicated three-dimensional flows such as separation, reattachment, and recirculation. CFX-5.4, a commercial code utilizing unstructured mesh, has been used as a computational method for solving RANS(Reynolds-Averaged Wavier-Stokes) equations, and the applied turbulence model is $k-{\varepsilon}$ model. In addition, those computational analyses were implemented under various conditions , with or without the vortex generator between two plates, the number, form and the size of vortex generator, and different attack of angle. From the calculated temperature, velocity and pressure distribution, vorticity, wall heat flux and so on under those conditions, this study shows the effect of vortex on heat transfer.

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