• Title/Summary/Keyword: CFD technique

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On the Visualization of Turbulent Structures Using CFD Technique (CFD 데이터를 이용한 난류구조의 가시화)

  • Na Yang
    • Journal of the Korean Society of Visualization
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    • v.2 no.2
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    • pp.20-24
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    • 2004
  • Recent advances in CFD technique along with a rapid growth of computer resources provide valuable opportunities for developing an accurate way of visualizing turbulent structures. Not only this visualization technique made it possible to check the validity of many of theoretical achievements of the past but also it pushes the current turbulence research to a new paradigm. A brief history of visualization study will be summarized and discussed.

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Store Separation Analysis of Flow Angularity Wind Tunnel Test Technique using CFD (1) (CFD를 활용한 Flow Angularity 풍동시험기법의 외장분리 해석(1))

  • Son, Chang-Hyeon;Seo, Sung-Eun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.45 no.1
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    • pp.10-20
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    • 2017
  • This study presents the feasibility of CFD(computational fluid dynamic) analysis using the flow angularity wind tunnel test technique. The CFD analyzed data by the flow angularity technique has been constructed as the database to get store trajectories by 6-DOF simulation. The database has been checked out store aerodynamic coefficients by the analyses at each position under wing. After that process, the simulated trajectories by database have been compared with the store trajectories by CTS(Captive Trajectory Simulation) of CFD. The trajectories provided by the database of flow angularity have a good agreement with the store trajectories by CFD.

파워 효과를 고려한 스마트 무인기의 공력해석

  • Kim, Cheol-Wan;Chung, Jin-Deog
    • Aerospace Engineering and Technology
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    • v.4 no.1
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    • pp.39-44
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    • 2005
  • To validate the rotor performance analysis, 3D Computational Fluid Dynamics(CFD) analysis was performed for tilt rotor aeroacoustic model(TRAM). Also, 3D vehicle with rotating rotors was simulated for rotor power effect analysis. Multiple reference frame(MRF) and sliding mesh techniques were implemented to capture the effect of rotor revolution. CFD results were compared with the wind tunnel test results to validate their accuracy. At helicopter mode, CFD analysis predicted lower thrust than the wind tunnel test but CFD results showed good agreement with the test result at cruise mode. Rotor power effect decreased the lift but did not change drag and pitching moment.

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Evaluating Effective Volume and Hydrodynamic Behavior in a Full-Scale Ozone Contactor with CFD Simulation (전산유체역학을 이용한 실규모 오존 접촉에서의 수리거동과 유효 체적 평가에 관한 연구)

  • Park, No-Suk;Mizuno, Tadao;Tsuno, Hiroshi;Bea, Chul-Ho;Lee, Seon-Ju
    • Journal of Korean Society of Water and Wastewater
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    • v.18 no.5
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    • pp.656-665
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    • 2004
  • An Ozone reaction model combined with CFD(Computational Fluid Dynamics) technique was developed in this research, in the simulation of ozonation, hydrodynamic behavior as well as reaction model is important because ozone is supplied to treated water as gas ozone. In order to evaluate hydrodynamic behavior in an ozone contactor, CFD technique was applied. CFD technique elucidated hydrodynamic behavior in the selected ozone contactor, which consisted of three main chambers. Three back-mixing zones were found in the contactor. The higher velocities of water were observed in the second and third compartments than that in the first compartment. The flow of the opposite direction to the main flow was observed near the water surface. Based on the results of CFD simulation, the ozone contactor was divided into small compartments. Mass balance equations were established were established in each compartment with reaction terms. This reaction model was intended to predict dissolved ozone concentration, especially. We concluded that the model could predict favorably the mass balance of ozone, namely absorption efficiency of gaseous ozone, dissolved ozone concentration and ozone consumption. After establishing the model, we discussed the effect of concentration of gaseous ozone at inlet, temperature and organic compounds on dissolved ozone concentration.

Torque Prediction of Ball Bearings Considering Cages using Computational Fluid Dynamics (전산유체역학을 이용한 케이지가 고려된 볼 베어링의 토크 예측)

  • Jungsoo Park;Jeongsik Kim;Seungpyo Lee
    • Tribology and Lubricants
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    • v.40 no.1
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    • pp.1-7
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    • 2024
  • Ball bearings are a major component of mechanical parts for transmitting rotation. Compared to tapered roller bearings, ball bearings offer less rolling resistance, which leads to reduced heat generation during operation. Because of these characteristics, ball bearings are widely used in electric vehicles and machine tools. The design of ball bearing cages has recently emerged as a major issue in ball bearing design. Cage design requires pre-verification of performance using theoretical or experimental formula or computational fluid dynamics (CFD). However, CFD analysis is time-consuming, making it difficult to apply in case studies for design decisions and is mainly used in performance prediction following design confirmation. To use CFD in the early stages of design, main-taining analytical accuracy while reducing the time required for analysis are necessary. Accordingly, this study proposes a laminar steady-state segment CFD technique to solve the problem of long CFD analytical times and to enable the use of CFD analysis in the early stages of design. To verify the reliability of the CFD analysis, a bearing drag torque test is performed, and the results are compared with the analytical results. The proposed laminar steady-state segment CFD technique is expected to be useful for case studies in bearing design, including cage design.

Transonic Flutter Suppression of the 2-D Flap Wing with External Store using CFD-based Aeroservoelasticity

  • Lee, Seung-Jun;Lee, In;Han, Jae-Hung
    • International Journal of Aeronautical and Space Sciences
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    • v.7 no.2
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    • pp.121-127
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    • 2006
  • An analysis procedure for the combined problem of control algorithm and aeroelastic system which is based on the computational fluid dynamics(CFD) technique has been developed. The aerodynamic forces in the transonic region are calculated from the transonic small disturbance(TSD) theory. An linear quadratic regulator(LQR) controller is designed to suppress the transonic flutter. The optimal control gain is estimated by solving the discrete-time Riccati equation. The system identification technique rebuilds the CFD-based aeroelstic system in order to form an adequate system matrix which involved in the discrete-time Riccati equation. Finally the controller, that is constructed on the basis of system identification technique, is used to suppress the flutter phenomenon of the airfoil with attached store. This approach, that is, the CFD-based aeroservoelasticity design, can be utilized for the development of effective flutter controller design in the transonic region.

EXAMPLES OF REDUCED ORDER MODELLING FOR A 3D BACKWARD FACING STEP FLOW USING POD TECHNIQUE (POD를 사용한 3차원 후향계단 유동장 분석 예제)

  • Lee, K.S.;Lee, E.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.40-42
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    • 2010
  • Unsteady CFD results of the backward facing step (BFS) flow field is reconstructed by the low-dimenstional modes using the POD (Proper Orthogonal Decomposition) technique. Flow responses to the blowing or suction with various frequencies and amplitudes applied at the edge of the BFS can also be analysed using the same technique. The present technique can be effectively applied to the feedback flow control device.

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Case study on Remodeling Clearwell Hydraulic Structure using Transient CFD Simulation Technique (Transient CFD 모사기법을 이용한 정수지 최적설계 사례연구)

  • Kim, Seon-Jin;Kim, Seong-Su;Park, No-Suk;Cha, Min-Whan;Wang, Chang-Keun
    • Journal of Korean Society of Water and Wastewater
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    • v.24 no.4
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    • pp.425-432
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    • 2010
  • From the results of tracer test for the existing clearwell in Y water treatment plant, $T_{10}$ and T10/T were calculated as 150 min and 0.24, respectively. Therefore it required the modification schemes for improving hydraulic efficiency, surrogated by $T_{10}$ and $T_{10}$/T, and disinfection performance. In this study, using transient CFD(Computational Fluid Dynamics) simulation technique, tracer tests on dynamic condition for the suggested schemes were simulated. From the results of simulation, it was revealed that 8~6 baffles are necessary to guarantee the disinfection ability in the existing clearwell. Also, installing orifice baffle in the vicinity of inlet could increase plug flow fraction within clearwell.

Thresholding for CFD data compression based on Supercompact Multiwavelets (Supercompact Multiwavelets 을 이용한 CFD 데이터 압축의 Thresholding)

  • Kwon, Do-Hoon;Lee, Do-Hyung
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.962-967
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    • 2003
  • CFD data compression method based on supercompact multiwavelets is presented. High data compression can be achieved when taking advantage of the compact nature of multiwavelets. Thresholding technique is also a matter of primary concern in determining pressure ratio. In this paper, we apply thresholding for multiwavelets that considers the coefficient vector as a whole rather than thresholding individual elements. Various thresholding methods are described briefly. CFD data compression suggests that the multivariate thresholding method is suitable for supercompact multiwavelets.

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Development of Analysis Technique for a High Voltage Circuit Breaker Using the CFD-CAD Integration (CFD-CAD 통합해석을 이용한 초고압 가스차단기 설계 기술 개발)

  • Lee, J.C.;Oh, I.S.;Min, K.S.;Kim, Y.J.
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.523-528
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    • 2001
  • There are many difficult problems in analyzing the flow characteristics in a high voltage circuit breaker such as shock wave and complex geometries, which may be either static or in relative motion. Although a variety of mesh generation techniques are now available, the generation of meshes around complicated, multicomponent geometries like a gas circuit breaker is still a tedious and difficult task for the computational fluid dynamics. This paper presents the computational method for analyzing the compressible flow fields in a high voltage gas circuit breaker using the Cartesian cut-cell method based on the CFD-CAD integration, which can achieve the accurate representation of the geometry designed by a CAD tools. The technique is frequently satisfied, and it will be almost universally so in the future, as the CFD-CAD traffic increases.

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