• Title/Summary/Keyword: 수치풍동

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Numerical Calculations of Three-dimensional Viscous Flows over a stern by the Semi-Elliptic Equations (준타원형 방정식에 의한 선미에서의 3차원 점성유동의 수치계산)

  • Shin-Hyoung,Kang;Keon-Je,Oh
    • Bulletin of the Society of Naval Architects of Korea
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    • v.26 no.1
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    • pp.11-23
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    • 1989
  • A computer code has been developed to simulate three-dimensional viscous flows over a ship-stern. Semi-elliptic forms of Reynolds equations are adopted and numerically generated body-fitted coordinate systems are used to resolve complex geometries of the ship-hull. A standard form of $k-\varepsilon$ turbulence model is adopted for evaluation of the Reynolds stresses. Turbulent flows on a model with 3:1 elliptic sections and the SSPA-720 container ship model are predicted by using the code. Calculated pressure distributions of hull-surfaces and mean velocity distributions are generally in good agreements with measured values in wind-tunnels. But turbulent kinetic energies tend to be over-estimated near the stern in comparison with measured data.

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A Study on Aeroacoustics and Its Applications (공력소음에 대한 연구 및 적용)

  • 이덕주;유기완
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.573-580
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    • 1997
  • 본 고에서는 공력음향학에 대한 여러 분야 중에서 최근 국내에서 관심 있게 연구되어온 분야에 대하여 그 연구 내용과 연구 방법 등을 소개하고자 한다. 먼저 전형적인 유체의 소음원에 대해서 설명하고, 이에 대한 수치적 해석방법과 무향풍동을 이용한 실험, 그리고 본 음향학 이론에 대한 응용 사례들에 대해서 간략히 소개하고자 한다.

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사용자탐방-한국과학기술원 항공우주공학전공 권장혁 교수

  • Jo, Geum-Won
    • Journal of Scientific & Technological Knowledge Infrastructure
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    • s.6
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    • pp.136-139
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    • 2001
  • 풍동과 같은 고가의 실험 장비가 필요하고 결과를 얻는데까지 많은 시간과 비용이 소요되는 단점이 있습니다. 전산유체역학은 이러한 문제점들을 보완할 수 있는 휼륭한 대안으로 인정받고 있습니다. 자연계에서 공기나 물 등의 유체가 우리의 관심 대상인 비행기, 자동차 등의 물체 주위를 흘러갈 때 생기는 물리 현상들은 보존의 법칙과 열역할 법칙에서 얻어지는 편미분 방정식들로 나타낼 수 있습니다. 이러한 자연계의 법칙을 나타내는 복잡한 방정식을 컴퓨터로 해석하여 데이터를 얻는 수치적인 실험 혹은 시물레이션을 전산유체역할 이라고 부릅니다.

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Test Research Using an IR Thermography Technique in a Supersonic Wind Tunnel (초음속 풍동에서의 IR Thermography 기법을 활용한 시험연구)

  • Kim, Ikhyun;Lee, Jaeho;Park, Gisu;Byun, Yunghwan;Lee, Jongkook
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.44 no.2
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    • pp.99-107
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    • 2016
  • Test research on Infra-Red Thermography(IRT) technique in a supersonic wind tunnel has been conducted. Inadvertent technical difficulties and their solutions associated with the technique in running of the facility were examined. Two flow conditions at Mach number of 3 and 4 were considered. A double compression ramp model, that replicates realistic high-speed vehicle configuration, was used as test model. The present IR data were compared with shadowgraph visualization images and laminar computational fluid dynamics(CFD) results. It has been shown that the IRT technique can be used in quantifying various fluid dynamic features such as flow transition, separation and three-dimensional phenomena around the double compression ramp model.

Rapid Estimation of the Aerodynamic Coefficients of a Missile via Co-Kriging (코크리깅을 활용한 신속한 유도무기 공력계수 추정)

  • Kang, Shinseong;Lee, Kyunghoon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.1
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    • pp.13-21
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    • 2020
  • Surrogate models have been used for the rapid estimation of six-DOF aerodynamic coefficients in the context of the design and control of a missile. For this end, we may generate highly accurate surrogate models with a multitude of aerodynamic data obtained from wind tunnel tests (WTTs); however, this approach is time-consuming and expensive. Thus, we aim to swiftly predict aerodynamic coefficients via co-Kriging using a few WTT data along with plenty of computational fluid dynamics (CFD) data. To demonstrate the excellence of co-Kriging models based on both WTT and CFD data, we first generated two surrogate models: co-Kriging models with CFD data and Kriging models without the CFD data. Afterwards, we carried out numerical validation and examined predictive trends to compare the two different surrogate models. As a result, we found that the co-Kriging models produced more accurate aerodynamic coefficients than the Kriging models thanks to the assistance of CFD data.

Blockage-Correction Method for Unsteady Flows in a Closed Test-Section Wind Tunnel (폐쇄형 풍동 시험부 내의 비정상 흐름에 대한 Blockage 보정 기법 연구)

  • Gang, Seung-Hui;Gwon, O-Jun;An, Seung-Gi
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.12
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    • pp.67-74
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    • 2006
  • An unsteady blockage-correction method utilizing wall pressure distribution on the test section has been developed for the wall interference correction of a closed test-section subsonic wind tunnel. The pressure distribution along the test section wall was decomposed into Fourier series and a quasi-steady method based on a measured-boundary-condition method was applied to each Fourier coefficient. The unsteady correction for a complete test period was accomplished by recombining each corrected terms. The present method was validated by appling computed unsteady flows over a cylinder and an oscillating airfoil in the test sections. The corrected results by the present method agreed well with free-air condition.

Eulerian-based Numerical Modeling for Impingement Prediction of Supercooled Large Droplets (과냉각대형액적 충돌예측을 위한 오일러리안 기반 수치 모델링)

  • Jung, Sung-Ki;Kim, Ji-Hong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.8
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    • pp.647-654
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    • 2012
  • Supercooled large droplet issues in aircraft icing have been continually reported due to the important safety considerations. In order to simulate the impingement behavior of large droplets, a two-dimensional and compressible Navier-Stokes code was developed to determine the flow field around the test model. Also, the Eulerian-based droplet impingement model including a semi-empirical approach for the droplet-wall interaction process and droplet break-up was developed. In particular, the droplet-wall interactions were considered as numerical boundary conditions for the droplet impingement simulation in the supercooled large droplet conditions. Finally, the present results were compared with the experimental test data and the LEWICE results. The droplet impingement area and maximum collection efficiency values between present results and wind tunnel data were in good agreements. Otherwise, the inclination of collection efficiency of the present result is over-predicted than the wind tunnel data around a lower surface of the NACA 23012 airfoil.

A NUMERICAL SIMULATION OF THE PRESSURE COEFFICIENT AROUND A CUBIC BUILDING MODEL (수치풍동 기법을 이용한 정사각형 건물 주위의 풍압계수에 관한 연구)

  • Yeo, Jae-Hyun;Hur, Nahm-Keon;Won, Chan-Shik;Kim, Sa-Ryang;Choi, Chang-Koon
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.162-166
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    • 2007
  • In the present study, the pressure coefficient of a cubic building model is numerically simulated. Three turbulence models of standard ${\kappa}-{\varepsilon}$, RNG ${\kappa}-{\varepsilon}$ and LES are adopted and the results are compared with the available experimental data. From the results, it has been found that RNG ${\kappa}-{\varepsilon}$ turbulence model and LES turbulence model were shown to predict fairly well the experimental pressure coefficient. In contrast, the results of the standard ${\kappa}-{\varepsilon}$ turbulence model showed large discrepancies in pressure coefficient on the side and top surfaces of the cubic building, which limits the applicability of the standard ${\kappa}-{\varepsilon}$ turbulence model on wind engineering.

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외부압축 초음속 흡입구에서 Spike-Tip과 Cowl-Lip의 형상에 따른 흡입구 성능에 대한 수치해석적 연구

  • Jo, Gyeong-Jun;Lee, Ji-Hong
    • Proceeding of EDISON Challenge
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    • 2015.03a
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    • pp.612-617
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    • 2015
  • 초음속 흡입구는 고속 비행에서 발생하는 충격파를 이용하여 제트엔진 내부에 유입되는 공기를 압축시키는 구조로써 주로 램제트와 스크램제트 엔진에 적용되어 연구개발이 진행되어 왔으며 현재는 미사일의 추진체 개발에도 응용되고 있다. 초음속 영역에서의 흡입구는 cone 모양의 스파이크 구조를 통해 경사충격파가 생성되어 외부에서의 공기압축을 먼저 거치게 된다. 본 연구에서는 EDISON CFD를 이용하여 외부압축 초음속 흡입구 주위의 공기유동을 해석하고 Cubbison, R.W.의 풍동실험 결과와 비교 분석하였다. 초음속 흡입구 주위의 유동을 2D 축대칭 압축성 유동으로 가정하고 EDISON CFD의 2D_Comp_P 솔버를 사용하여 수치해석을 수행하였다.

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Numerical Simulation and Experiment on Supersonic Air-Breathing Laser-Spike Propulsion Vehicle (초음속 공기 흡입식 레이저 스파이크 추진 비행체에 관한 수치 해석 및 실험적 연구)

  • Kim Sukyum;Kim Young-Taek;Jeong In-Seock
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.10a
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    • pp.57-61
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    • 2004
  • As a kind of application of laser propulsion, air-breathing laser-spike engine can be designed for aircraft in atmospheric flight. Laser-spike engine generates thrust using the blast wave induced by laser energy instead of combustion process. And this engine use air as propellant, therefore, it need no on board propellant. For experimental study, supersonic wind tunnel and spark generator were used. Flow visualization was performed using 2-dimensional laser-spike engine model And numerical simulation of the corresponding case for the experiment was done and compared with experimental case. Detailed results will be discussed at the presentation.

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