• Title/Summary/Keyword: 수치풍동

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An Establishment of Canard-Leading Edge Flap Scheduling Law Based on Experimental and Numerical Studies For the Aerodynamic Design of Canard Type Fighter Class Aircraft (카나드 형상 전투기급 항공기 공력설계를 위한 실험 및 수치해석적 카나드-앞전플랩 스케줄링 법칙 수립)

  • Chung, In-Jae;Kim, Sang-Jin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.7
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    • pp.655-660
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    • 2007
  • A canard-leading edge flap deflection scheduling laws have been established to enhance the maneuverability of the canard type fighter class aircraft. These scheduling laws are the relation of canard-leading edge flap deflections and flight conditions to maximize the lift-drag ratio. For these purposes, the corrected supersonic panel method has been used to predict the lift-drag characteristics due to canard-leading edge flap deflections. In addition, the high speed wind tunnel test has been conducted with 1/20 scale model to validate the predicted scheduling laws. Good agreements have been obtained compared with the results of high speed wind tunnel test. Based on the results obtained from the experimental and numerical studies, the corrected supersonic panel method has shown to be useful to establish the canard-leading edge flap deflection scheduling law for the aerodynamic design of canard type fighter class aircraft.

Numerical Simulation of Plume Dispersion Over a Hilly Terrain (언덕지형에서 연기확산의 수치모사)

  • 김현구;이정묵;최돈범
    • Proceedings of the Korea Air Pollution Research Association Conference
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    • 2002.04a
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    • pp.279-280
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    • 2002
  • 본 연구에서는 라그랑지안 확산모델(LDM; Lagrangian dispersion model)을 이용하여 평지 및 언덕지형에서의 연기확산을 수치모사하였다. 수치예측의 검증을 위하여 평지지형의 경우는 풍동실험 결과와 비교하고 언덕지형의 경우는 오일러리안 확산모델(EDM; Eulerian dispersion model)의 모사결과와 비교함으로써 언덕지형에서 오염물질의 확산특성을 연구하였다. (중략)

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Study on the Hysteretic Behaviors of Shock Wave in a Supersonic Wind Tunnel (초음속 풍동에서 발생하는 충격파의 히스테리시스 현상에 관한 연구)

  • Lee, Ik In;Han, Geu Roo;Kim, Teo Ho;Kim, Heuy Dong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.2
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    • pp.52-58
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    • 2018
  • Hysteresis phenomena are often encountered in a wide variety of fluid flow systems used in industrial and engineering applications. Hence, in recent years, a significant amount of research been focusing on clarifying the physics of the flow hysteresis appearing during the transient change of the pressure ratios and influencing the performance of the supersonic wind tunnel. However, investigations on the hysteresis phenomenon, particularly when it occurs inside the supersonic wind tunnel, are rare. In this study, numerical simulations were carried out to investigate the hysteresis phenomena of the shock waves encountered in a supersonic wind tunnel. The unsteady and compressible flow was analyzed with an axisymmetric model, and the N-S equations were solved by using a fully implicit finite volume scheme. The optimal pressure ratio was determined from the hysteresis curves, and the results can be utilized to operate the wind tunnel efficiently.

Design of Supersonic Wind Tunnel for Analysis of Flow over a Backward Facing Step with Slot Injection (슬롯 분사가 있는 후향계단 유동장 분석을 위한 초음속풍동 설계)

  • Kim, Ick-Tae
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.11
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    • pp.363-367
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    • 2016
  • A test section of a supersonic wind tunnel was designed for the analysis of flow characteristics over a backward-facing step with Mach 1.0 slot injection in a supersonic flow of Mach 2.5. The cavity flow of a high-speed vehicle is very complex at supersonic speed, so it is necessary to do experiments using supersonic wind tunnels to verify numerical analysis methods. The previous 2D symmetrical nozzle was replaced with an asymmetrical nozzle. The inviscid nozzle contour was designed using Method of Characteristics (MOC), and the boundary layer thickness correction was reflected by experimental data from the wind tunnel. The results were compared with a CFD analysis. The PID control system was changed to be based on the change of tank pressure. This improved the control efficiency, and the run times of supersonic flow increased by about 1 second. The flow characteristics over a backward facing step with slot injection were visualized by a Schlieren device. This equipment will be used for an experimental study of the film cooling effectiveness over a cavity with various velocities, mass flows, and temperatures.

A Numerical Study on Wind Pressure Characteristics of Super-tall Protype Model considering the Effect of Turbulence Intensity (난류강도의 영향을 고려한 초고층 프로토타입 모델의 풍압특성에 관한 수치 해석적 연구)

  • Jeong, So-Young;Lee, Kyung-Soo;Han, Sang-Eul
    • Journal of Korean Society of Steel Construction
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    • v.23 no.6
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    • pp.659-667
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    • 2011
  • Wind tunnels tests have been evaluating wind load estimation by discussing the most important design elements in very tall buildings. Such tests have some uncertainties, however, with respect to the data of the reduced model and the calculated empirical values. In contrast, CFD analysis can simulate the actual scale and shorten the time of simulation. Nevertheless, the utilization of CFD analysis is negligible because of its low reliability. In this paper, the reliability of CFD analysis will be proven by comparing the results of a wind tunnel test and CFD analysis for the prototype models shown in previous studies. The effect of the turbulence intensity on the reliability is also presented.

A Study of Flare Operation Method for The Fighter with An External Center Fuel Tank (동체 중앙에 연료탱크를 장착한 전투기의 섬광탄 운용 방안 연구)

  • Kang, Chi-Hang;Jang, Young-Il;Kwon, Ky-Beom;Yoon, Young-In
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.7
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    • pp.616-622
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    • 2012
  • In this paper, we examined the problems of the flare operation of tactic maneuvering flight of fighter aircraft with 150GL center external fuel tank and proposed the possible solution of it's operation. The damage scope of horizontal fin of fuel tank and flare trajectory when the flare ejected from the maneuvering aircraft were analyzed by the wind tunnel test and the numerical analysis. We investigated the two different option to avoid the damage of fin; i) the adjustment of flare dispenser angle and ii) the change of horizontal fin's shape. For the considering of practical operation of present system, we chose the second option. We estimated the drop safety of external fuel tank with redesigned fin by the wind tunnel experiments.

Unsteady Wall Interference Effect on Flows around a Circular Cylinder in Closed Test-Section Wind Tunnels (폐쇄형 풍동 시험부내의 원형 실린더 유동에 대한 비정상 벽면효과 연구)

  • Kang, Seung-Hee;Kwon, Oh-Joon;Hong, Seung-Kyu
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.7
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    • pp.1-8
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    • 2005
  • For study on the unsteady wall interference effect, flows around a circular cylinder in closed test-section wind tunnels have been numerically investigated by solving compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with the Roe's flux-difference splitting and an implicit time-integration method coupled with dual time-step sub-iteration. The computed results showed that the unsteady pressure gradient over the cylinder is enhanced by the wall interference, and as a result the fluctuations of lift and drag are augmented. The drag is further increased because of the lower base pressure. The vortex shedding frequency is also increased by the wall interference. The pressure on the test section wall shows the harmonics having the shedding frequency contained in the wall effect.

Computational Analysis of Vortex Structures around Wall-Mounted Bluff Body in Boundary Layer (경계층 내에 위치한 각진 물체 주위의 와류 전산 해석)

  • Lee, Ju-Yong;Kim, Hyeon-U;Lee, Seung-Su
    • Proceeding of EDISON Challenge
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    • 2013.04a
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    • pp.354-359
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    • 2013
  • 일반적으로 건축물의 설계시 풍동 실험을 통한 풍환경의 평가를 수행하고 있으며, 이는 환경 영향 평가법에서 정한 건축 사업 시행 시 수반되어야 할 자연환경, 생활환경 그리고 사회경제환경의 영향 평가의 일환으로 실시되고 있다. 그러나, 풍동 실험의 경우 여러 가지 현실적 제약조건으로 설계와 실험의 피드백 (Feedback)이 원활하지 못하며, 특히 대상 건축물이 공장과 같이 대기 오염원이 되는 경우 실험은 더욱 어려운 형편이다. 이에 대한 보완책으로 전산 유체 역학을 이용한 건축물의 풍압 해석에 의한 풍하중 추정이나 인접 지형-지물의 영향을 고려한 건축물 주위의 풍환경 평가가 있다. 전산 모사에 의해 풍동 실험의 미비점을 보완하고, 보다 상세한 정보를 확보함으로써 건축물의 구조적 안전성의 증대와 환경 피해 감소를 기할 수 있다. 그러나 복잡한 지형-지물이나 건축물 주위의 풍환경에 대한 전산 모사는 주로 두 가지의 기술적 어려움을 수반하게 되다. 그 중 하나는 고정 경계면을 이루는 형상의 복잡성으로 인해 기존에 많이 이용하고 있는 Body-fitted 격자계를 이용하는 경우, 격자 생성 과정이 매우 복잡하고 어려울 뿐 만 아니라 생성된 격자가 주로 비정렬 (unstructured) 특성을 갖게 되어 수치해석 과정의 효율을 저하시키는 요인이 되며, 격자의 형상도 수치해석의 수렴성을 저하시키는 예가 많다. 다른 어려움으로 풍환경은 전형적인 난류 유동장으로서 난류의 전산 해석은 아직도 해결하지 못한 부분이 많다는 점이다. 이에 본 논문에서는 복잡한 지형-지물이나 건축물의 풍하중과 풍환경의 전산 모사 기술 확보를 위하여 수행중인 연구의 일환으로 물체 형상의 기하학적 복잡성의 극복을 위한 가상경계법 (Immersed Boundary Method)과 난류 유동장의 물리적 엄밀성을 높이기 위한 다와동 모사 (Large Eddy Simulation)을 이용한 물체 형상과 무관한 유동장 해석 기술 개발에 대하여 다루고자 한다. 먼저 최근에 유동 해석에 이용되는 방법인 가상경계법(IBM)은 물체를 포함한 전체 전산 영역을 직교 좌표계에 의해 이산화하고, 유동장내 존재하는 물체의 표면에서의 점착 조건을 만족시키기 위하여 지배 방정식에 적절한 외력을 추가로 고려하는 방법이다. 본 연구에서는 가상경계법을 이용하여 경계층에 위치한 건물 형상의 각진 물체 주위 사이에 형성되는 공동 내부의 비정상 유속 및 압력에 대한 전산 해석을 수행하고, 풍상측 전면에 형성되는 경계층에 의한 영향을 분석하였다.

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Numerical Study of the Aerodynamic Characteristics of an Airfoil with Thickness Uncertainty for a Wind Tunnel Testing (두께의 불확실성을 갖는 풍동시험 익형모델의 공력특성에 관한 수치해석 연구)

  • Yi, Tae-Hyeong;Kwon, Ki-Jung;Kim, Keun-Taek;Ahn, Seok-Min
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.6
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    • pp.475-484
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    • 2012
  • Numerical investigation is performed to understand the effects of thickness uncertainty of a supporting airfoil due to manufacturing processes on the aerodynamic characteristics of an airfoil used for measuring data in a wind tunnel testing. This is done by comparing the coefficients of lift, drag and moment of the airfoils. In this work, the airfoil model consists of three parts, one located in the center for measuring and two outer parts used for supporting. The study is carried out with a NACA64-418 airfoil and the turbulence model of Transition SST. It is found that the effect of thickness uncertainty of the airfoils used for supporting is not significant to the performance of the test airfoil at various angles of attack and Reynolds numbers.

Belly Sting Model Support Interference Effect of NASA Common Research Model at Low Speed Wind Tunnel (저속 풍동시험 시 NASA Common Research Model의 Belly Sting 모형 지지부에 의한 간섭효과에 관한 연구)

  • Cha, Kyunghwan;Kim, Namgyun;Ko, Sungho
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.3
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    • pp.167-174
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    • 2021
  • Computational Fluid Dynamics (CFD) was performed under low-speed wind tunnel test conditions using a 29.7% scale model of the NASA common research model. A wind tunnel test was conducted to measure the aerodynamic coefficient of the CRM with Belly sting model support configuration at a low Reynolds number of 0.3×106 and it was compared with the aerodynamic coefficient of CFD analysis. In order to verify the validation of the analysis, a computational analysis under the conditions of the advance research was performed and compared. The interference effect of the Belly sting model support affected not only the fuselage but also the main and tail wings.