• Title, Summary, Keyword: CFD calculation

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A comparative analysis of the total window thermal transmittance simulation result according to the evaluation method of effective conductivity(λeff) of frame cavity - Focused on unventilated frame cavity simulation results of single window - (창틀 공기층의 유효 열전도율(λeff) 산정방법 차이가 창 전체 열관류율(Uw) 시뮬레이션 결과에 미치는 영향에 대한 비교 분석 - 단창 창틀의 비환기 공기층에 대한 시뮬레이션을 중심으로 -)

  • Lee, Yong-jun;Oh, Eun-joo;Kim, Sa-kyum;Choi, Gyeong-seok;Kang, Jae-sik
    • KIEAE Journal
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    • v.16 no.2
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    • pp.79-85
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    • 2016
  • Purpose: It is difficult to calculate frame U-value because of the two reason. First is selection of air properties in cavity. Second is calculation method in window frame. For this reason, it is important to decide cavity properties in window frame. However, international standards offered different method(ISO 15099, ISO 10077) and air properties was changed according to the two methods. The aim of this study was to suggest method for deriving accurate frame U-value using international standard methods and CFD simulation. Method: First, this study conducted analysis calculation method of ISO 15099 and ISO 10077. And, CFD simulation conducted based on same condition. Finally, ISO calculation and CFD simulation results were verified through comparison with real experiment results. Result: The results show that effective conductivity of ISO 15099 was the highest value. ISO 10077 and CFD result followed. The convergent values of ISO 10077 was the highest. ISO 15099 and CFD followed. ISO calculation reflecting CFD simulation results will reduce error with experimental results.

Evaluation of Head Loss within In-Line Mixer for Water Treatment using CFD Technique (CFD모사 기법을 이용한 관내 혼화장치내 수두손실 발생 특성 평가)

  • Hwang, Young-Jin;Lim, Sung-Eun;Kim, Seong-Su;Park, No-Suk;Wang, Chang-Keun
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.1
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    • pp.107-112
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    • 2009
  • This study was conducted for verification and systematization of estimation method about the headloss using CFD(Computational Fluid Dynamics). Head loss which happens between the inlet and outlet of in-line mixer can be a major factor for the design and construction. Also, this Case studies about the sensitivity related to the velocity in the piping system. As result, program's default calculation function was used to get each side's total pressure and the differential of each total pressure could be defined as head loss from in-line mixer. In the case of adopting pipe surface friction factor and geometry loss, Calculation residual can be much more reduced. It was found that residual of value between CFD method and field test ranged about 3 through 18 precent.

Evaluation of the added mass for a spheroid-type unmanned underwater vehicle by vertical planar motion mechanism test

  • Lee, Seong-Keon;Joung, Tae-Hwan;Cheon, Se-Jong;Jang, Taek-Soo;Lee, Jeong-Hee
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.3 no.3
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    • pp.174-180
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    • 2011
  • This paper shows added mass and inertia can be acquired from the pure heaving motion and pure pitching motion respectively. A Vertical Planar Motion Mechanism (VPMM) test for the spheroid-type Unmanned Underwater Vehicle (UUV) was compared with a theoretical calculation and Computational Fluid Dynamics (CFD) analysis in this paper. The VPMM test has been carried out at a towing tank with specially manufactured equipment. The linear equations of motion on the vertical plane were considered for theoretical calculation, and CFD results were obtained by commercial CFD package. The VPMM test results show good agreement with theoretical calculations and the CFD results, so that the applicability of the VPMM equipment for an underwater vehicle can be verified with a sufficient accuracy.

Analysis of SLF Interruption Performance of Self-Blast Circuit Breaker by Means of CFD Calculation

  • Kim, Hong-Kyu;Chong, Jin-Kyo;Lee, Se-Hee
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.254-258
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    • 2014
  • This paper presents the performance analysis results of a short line fault interruption of a gas circuit breaker, particularly a self-blast type breaker. Hot gas flow analysis was carried out using a CFD calculation combined with the arc model and nozzle ablation model. To evaluate the interruption performance, the index function was defined using the pressure in the heating chamber and the density above the arc region. The simulation and test results showed that the gas flow field and suitable choice of an interruption performance index can be used to predict the interruption characteristics and provide guidelines for designing self-blast breakers with a higher interruption capability.

Aerodynamic Shape Design of a Partial Admission Turbine Using CFD (CFD를 이용한 부분흡입형 터빈 공력형상 설계)

  • Lee, Eun-Seok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.11
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    • pp.1131-1138
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    • 2006
  • Aerodynamic shape design of a partial admission turbine using CFD has been performed. Two step approaches are adopted in this study. Firstly, two-dimensional blade shape is optimized using CFD and genetic algorithm. Initially, the turbine cascade shape is represented by four design parameters. By controlling the design parameters as variables, the non-gradient search is analyzed for obtaining the maximum efficiency. The final two-dimensional blade proved to have a more blade power than the initial blade. Secondly, the three-dimensional CFD analysis including the nozzle, rotor and stator has been conducted. To avoid a heavy computational load due to an unsteady calculation, the frozen rotor method is implemented in steady calculation. The frozen rotor method can detect a variation of the flow-field dependent upon the blade's circumferential position relative to the nozzle. It gives a better idea of wake loss mechanism starting from the lip of the nozzle than the mixing plane concept. Finally, the combination of two and three dimensional design method of the partial admission turbine in this study has proven to be a robust tool in development phase.

A High-efficiency Trim Method for CFD Numerical Calculation of Helicopter Rotors

  • Ye, Zhou;Xu, Guo-hua;Shi, Yong-jie;Xia, Run-ze
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.2
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    • pp.186-196
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    • 2017
  • In order to resolve the trimming difficulty in rotor CFD calculations, a high-efficiency and improved "delta trim method" is established to compute the blade control settings that are necessary to identify the blade motion. In this method, a simplified model which combines the blade element theory and different inflow models is employed to calculate the control settings according to the target aerodynamic forces, then it is coupled into a CFD solver with unsteady Navier-Stokes equations by the delta methodology, which makes the control settings and aerodynamics calculated and updated in the meantime at every trim cycle. Different from the previous work, the current research combines the inflow model based on prescribed wake theory. Using the method established, the control settings and aerodynamic characteristics of Helishape 7A, AH-1G and Caradonna-Tung rotors are calculated. The influence of different inflow models on trimming calculations is analyzed and the computational efficiency of the current "delta trim method" is compared with that of the "CFD-based trim method". Furthermore, for the sake of improving the calculation efficiency, a novel acceleration factor method is introduced to accelerate the trimming process. From the numerical cases, it is demonstrated that the current "delta trim method" has higher computational efficiency than "CFD-based trim method" in both hover and forward flight, and up to 70% of the amount of calculation can be saved by current "delta trim method" which turns out to be satisfactory for engineering applications. In addition, the proposed acceleration factor shows a good ability to accelerate the trim procedure, and the prescribed wake inflow model is always of better stability than other simple inflow models whether the acceleration factor is utilized in trimming calculations.

CFD/Kirchhoff Integral Method for the Prediction of the Air-Pumping Noise by a Car Tyre (CFD/Kirchhoff 적분 방법을 이용한 자동차 타이어의 Air-Pumping 소음 예측)

  • Kim, Sung-Tae;Lee, Soo-Gab
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.916-919
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    • 2004
  • The monopole theory has long been used to model air-pumped effect from the elastic cavities in car tire. This approach models the change of an air as a piston moving backward and forward on a spring and equates local air movements exactly with the volume changes of the system. Thus, the monopole theory has a restricted domain of applicability due to the usual assumption of a small amplitude acoustic wave equation and acoustic monopole theory. This paper describes an approach to predict the air-pumping noise of a car ave with CFD/Kirchhoff integral method. The type groove is simply modeled as piston-cavity-sliding door geometry and with the aid of CFD technique flow properties in the groove of rolling car tyre are acquired. And these unsteady flow data are used as a air-pumping source in the next Cm calculation of full tyre-road geometry. Acoustic far field is predicted from Kirchhoff integral method by using unsteady flow data in space and time, which is provided by the CFD calculation of full tyre-road domain. This approach can cover the non-linearity of acoustic monopole theory with the aid of using Non-linear governing equation in CFD calculation. The method proposed in this paper is applied to the prediction of air-pumping noise of modeled car tyre and the predicted results are qualitatively compared with the experimental data.

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A Study on Three-Dimensional Flow Characteristics and Power Performance of HAWT(Horizontal Axis Wind Turbine) by CFD (CFD를 이용한 풍력발전 터빈의 3차원 유동해석 및 성능평가에 관한 연구)

  • Kim Beom-Seok;Kim Jeong-Hwan;Nam Chung-Do;Lee Young-Ho
    • Proceedings of the KSME Conference
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    • pp.447-450
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    • 2002
  • The purpose of this 3-D numerical simulation is to calculate and examine a 500 kW Horizontal Axis Wind Turbine (HAWT) power performance and 3-D rotor flow characteristics, which are compared to calculation data from Delft University. The experimental approach, which has been the main method of investigation, appears to be reaching its limits, the cost increasing relate with the size of wind turbines. Hence, the use of Computational Fluid Dynamics (CFD) techniques and Navier-Stokes solvers is considered a very serious contender. We has used the CFD software package CFX-TASCflow as a modeling tool to predict the power performance and 3-D flow characteristics of a wind turbine on the basis of its geometry and operating data. The wind turbine with 40m diameters rotor, it was scaled to compare with the calculation data from delft university. The HAWT, which has eight-rpm variations are investigated respectively. The pitch angle is $+0.5^{\circ}$and wind speed is fixed at 5m/s. The tip speed ratio (TSR) of the HAWT ranging from 2.89 to 9.63.

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Numerical Method for Prediction of Air-pumping Noise by Car Tyre (자동차 타이어의 Air-Pumping소음 예측을 위한 수치적 기법)

  • Kim, Sungtae;Jeong, Wontae;Cheong, Cheolung;Lee, Soogab
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.7
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    • pp.788-798
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    • 2005
  • The monopole theory has long been used to model air-pumped effect from the elastic cavities in car tire. This approach models the change of an air as a Piston moving backward and forward on a spring and equates local air movements exactly with the volume changes of the system. Thus, the monopole theory has a restricted domain of applicability due to the usual assumption of a small amplitude acoustic wave equation and acoustic monopole theory This paper describes an approach to predict the air-pumping noise of a car tyre with CFD/Kirchhoff integral method. The tyre groove is simply modeled as piston-cavity-sliding door geometry and with the aid of CFD technique flow properties in the groove of rolling car tyre are acquired.'rhese unsteady flow data are used as a air-pumping source in the next CFD calculation of full tyre-road geometry. Acoustic far field is predicted from Kirchhoff integral method by using unsteady flow data in space and time which is provided by the CFD calculation of full tyre-road domain. This approach can cover the non-linearity of acoustic monopole theory with the aid of Non-linear governing equation in CFD calculation. The method proposed in this paper is applied to the prediction of air-pumping noise of simply modeled car tyre and through the predicted results, the influence of nonlinear effect on air-pumping noise propagation is investigated.

Recalculation of the Particle Dynamic Model for Gas-Solid Cyclone (싸이클론에 대한 입자운동방정식의 재계산)

  • Lee, Kyung-Mi;Jang, Jung-Hee;Jo, Young-Min;Kim, Chang-Nyung
    • Journal of Korean Society for Atmospheric Environment
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    • v.23 no.6
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    • pp.708-717
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    • 2007
  • In the present study, one of the widely applied equations for gas-solid cyclones, Leith and Licht model, was evaluated based on the 3-D CFD technique. The initial and boundary values of radial position and tangential velocity obtain-ed from the CFD simulation enabled complete calculation of the nonlinear second differential equation. This approach showed about 30% errors between calculations with and without the second order differential term. The calculation by using the simple first order equation presented shorter times to migrate up to the inner wall of the cyclone than by the second order, which theoretically implies higher separation efficiency. Further comparison is now under evaluation in terms of the detailed grade efficiency.