• Title/Summary/Keyword: 비대칭 와류

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The Numerical Analysis of Asymmetric Vortices around the Slender body at High Angle of Attack Supersonic Flow (고받음각 초음속 유동에서의 세장형 몸체 주변에 발생하는 비대칭와류에 대한 수치적 연구)

  • Jeon, Young-Jin;Ji, Young-Moo;Kim, Ki-Su;Seo, Hyung-Seok;Byun, Yung-Hwan;Lee, Jae-Woo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2007.04a
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    • pp.335-338
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    • 2007
  • In the case of an antiaircraft missile, high angle of attack flight capability is required to get the agile maneuverability in a supersonic flow. Even through a symmetric slender body does not have side slip, asymmetric vortex is generated at high angle of attack conditions. This asymmetric vortex produces unnecessary side force and yawing moment; hence, these effects deteriorate directional stability. In this study, the numerical analysis of asymmetric vortices around the slender body was conducted at high angle of attack supersonic flow. In order to simulate the vortices, a bump is installed on the nose of the slender body. As a result of the numerical analysis, the asymmetric vortices around the slender body could be simulated.

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A Study on the Improvement of Wave and Storm Surge Predictions Using a Forecasting Model and Parametric Model: a Case Study on Typhoon Chaba (예측 모델 및 파라미터 모델을 이용한 파랑 및 폭풍해일 예측 개선방안 연구: 태풍 차바 사례)

  • Jin-Hee Yuk;Minsu Joh
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.35 no.4
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    • pp.67-74
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    • 2023
  • High waves and storm surges due to tropical cyclones cause great damage in coastal areas; therefore, accurately predicting storm surges and high waves before a typhoon strike is crucial. Meteorological forcing is an important factor for predicting these catastrophic events. This study presents an improved methodology for determining accurate meteorological forcing. Typhoon Chaba, which caused serious damage to the south coast of South Korea in 2016, was selected as a case study. In this study, symmetric and asymmetric parametric vortex models based on the typhoon track forecasted by the Model for Prediction Across Scales (MPAS) were used to create meteorological forcing and were compared with those models based on the best track. The meteorological fields were also created by blending the meteorological field from the symmetric / asymmetric parametric vortex models based on the MPAS-forecasted typhoon track and the meteorological field generated by the forecasting model (MPAS). This meteorological forcing data was then used given to two-way coupled tide-surge-wave models: Advanced CIRCulation (ADCIRC) and Simulating Waves Nearshore (SWAN). The modeled storm surges and waves correlated well with the observations and were comparable to those predicted using the best track. Based on our analysis, we propose using the parametric model with the MPAS-forecasted track, the meteorological field from the same forecasting model, and blending them to improve storm surge and wave prediction.

Analysis of Vortex Vibration by Using the FSI Technique (FSI 기법을 이용한 와류진동 해석)

  • Kim, Dae-Geun;Kim, Sung-Man
    • Proceedings of the Korea Water Resources Association Conference
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    • 2010.05a
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    • pp.754-758
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    • 2010
  • 케이블 교량에서 발생하는 사장케이블의 진동현상에 대한 현상학적 특성을 명확히 이해해야, 사장케이블의 적합한 제진설계가 가능하다. 본 연구에서는 유체의 흐름과 구조물의 진동을 동적으로 연계하여 해석하기 위하여, ADINA의 CFD 및 Structure 코드를 동적으로 연계하는 FSI(Fluid Flow with Structure Interaction) 기법을 이용하였다. 바람으로 인해 이중원형실린더의 풍상측과 풍하측 실린더에서는 와류가 방출되면서 외력이 작용하게 되며, 이러한 공기력은 풍하측 실린더의 고유진동 운동과 함께 와류진동현상을 유발한다. 본 연구에서는 풍하측 실린더의 와류진동 현상의 해석에 주안점을 두었다. 본 연구에서는 흐름의 레이놀즈수와 이중원형실린더에 대한 바람의 입사각을 변화시키며 풍하측 실린더에서 발생하는 와류진동의 크기를 분석하였다. 본 연구결과, 유입풍속 및 바람의 입사각에 따라 이중원형실린더에서 발생하는 일반적인 와류방출현상과 풍하측 실린더에 작용하는 공기력 및 변위양상을 예측할 수 있었다. 특히, 바람의 입사각이 $15^{\circ}$인 경우에는 풍하측 실린더에서 방출되는 와류로 인해 풍하측 실린더에는 비대칭의 공기력이 작용하며, 이는 풍하측 실린더가 2사분면에서 4사분면 방향으로 진동하는 원인이 되는 것으로 판단된다.

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Wake Structure of Tip Vortex Generated by a Model Rotor Blade of NACA0015 Airfoil Section (NACA0015익형을 가지는 로터 깃 끝와류의 후류유동구조)

  • Sohn, Yong-Joon;Kim, Jeong-Hyun;Han, Yong-Oun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.3
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    • pp.210-217
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    • 2011
  • Evolution of tip vortex generated by a model rotor blade which has a symmetric blade section has been investigated by use of the laser doppler anemometry. Swirl and axial velocity components of tip vortex were measured by the phase averaging technique within one revolution of a rotor blade. It was found that tip vortex becomes matured until 27 degrees and diffuses afterwards with diffusing rate becoming slower compared to the case of the asymmetric blade section, but the tip loss was expected to become more substantial. Swirl velocity components were well fit to n=2 model of Vatistas within measured wake ages, showing the self-similarity exists for the swirl velocity components. The axial components were followed with Gaussian profiles, but had much higher peak values than those of the symmetric blade section.

ASYMMETRIC VORTEX CHARACTERISTICS AT A CONE UNDER SUPERSONIC HIGH ANGLE OF ATTACK FLOW (초음속 고받음각에서의 원뿔형 물체 주위의 비대칭 와류 특성 연구)

  • Park, M.Y.;Noh, K.H.;Park, S.H.;Lee, J.W.;Byun, Y.H.
    • Journal of computational fluids engineering
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    • v.13 no.2
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    • pp.8-13
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    • 2008
  • A supersonic viscous flow over a five-degree half-angle cone is studied computationally with three-dimensional Navier-Stokes equations. Steady asymmetric solutions show that the asymmetric flow separation is caused by convective instability. The effects of angle of attacks, Reynolds numbers, and Mach numbers have been investigated and it is found that those factors affect the generation of the side force. The side force has the maximum value at ${\alpha}=22^{\circ}$, while over ${\alpha}=22^{\circ}$, asymmetric vortex becomes transient, which results in the unsteady shedding. At the angle of attack of 22 degrees, the side force increases with Reynolds number and decreases with Mach number. The increase of the side force stops over the critical Reynolds number for the present configuration.

Effect of the Flow Actuator on the Asymmetric Vortex at High Angle of Attack (고받음각 오자이브의 비대칭 와류에 작용하는 구동기 효과 분석)

  • Lee, Eunseok;Lee, Jin Ik;Lee, Kwang Seop
    • Journal of the Korea Institute of Military Science and Technology
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    • v.16 no.5
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    • pp.607-612
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    • 2013
  • The effect of the flow actuator on the asymmetric vortex structure around the ogive-cylinder body with fineness ratio of 4 flying at the speed of Mach 0.1 at angle of attack of 50 degree is studied. The ogive-cylinder model is developed with the actuator placed near the nose tip and numerically simulated using the in-house CFD code named KFLOW. The numerical simulation employs two different actuator modeling: one is the boundary condition given by blowing normal to the surface and another shearing on the surface. The numerical simulation reveals that response of the vortex structure to the actuation is dependent on the type of modeling as well as the strength and direction of the actuation.

NUMERICAL ANALYSIS FOR STEADY ASYMMETRIC VORTEX OF CONE AT HIGH ANGLE OF ATTACK (고받음각에서 원뿔형 물체 주위에 발생하는 정상상태 비대칭 와류의 수치해석)

  • Park, M.Y.;Park, S.H.;Lee, J.W.;Byun, Y.H.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.171-176
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    • 2007
  • Supersonic viscous flow over a 5 degree half angle cone studied computationally with three-dimensional Navier-Stokes equations. Steady asymmetric solutions of 5-deg half angle cone show that the asymmetric flow separation is caused by convective instability. The angle of attack, Reynolds number, and Mach number affected the side force variation that is caused by asymmetric vortical flow.

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Asymmetric Vortices around a Body at High Angle of Attack Subsonic Flow (아음속 유동하의 고 받음각 물체 주위의 비대칭 와류 특성 연구)

  • Park, Mee-Young;Kim, Wan-Sub;Lee, Jae-Woo;Park, Soo-Hyung
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.33-38
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    • 2008
  • Numerical investigation of asymmetric vortices at high angles of attack subsonic flow is performed using three-dimensional Navier-Stokes equations. A small bump has been carefully selected and attached near the nose of an ogive cylinder to simulate symmetric vortices. Selected bump shape does develop asymmetric vortices and is verified using Lamont's experimental results. By changing the angle of attack, Reynolds numbers, and Mach numbers, the characteristics of asymmetric vortices are observed. The angle of attack which contributes significantly to the generation of asymmetric vortices are over 30 degrees. By increasing Mach number and Reynolds number asymmetric vortices, hence the side forces show decreasing trend..

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An Experimental Study of Asymmetric Vortices around Slender Bodies during High Angle of Attack Maneuver (세장형 몸체의 고받음각 기동에서 발생하는 비대칭와류에 관한 실험적 연구)

  • Jeon, Young-Jin;Seo, Hyung-Seok;Choi, Wom-Hyeok;Byun, Yung-Hwan;Lee, Jae-Woo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.71-76
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    • 2008
  • In this study, side force, drag, and the yawing moment were measured based on the angle of attack by using two models of different nose shapes with slender bodies, which were general shapes in the subsonic area. As a result, the side force and yawing moment were the highest at a specific angle of attack. The boundary between asymmetrical normal state and asymmetrical abnormal state were able to be seen. As a result of analyzing the side force, drag, and yawing moment by time, reliability varied depending on the shape of the head at the same angle of attack. The results of measuring pressure distribution from the surface of the slender body at each angle of attack were as follows: as the angle of attack gets higher, the distribution of surface pressure was asymmetrical.

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Papers : Effect of Sideslip on the Vortex Flow over a Delta Wing (논문 : 옆미끄럼각이 삼각 날개 와류에 미치는 영향)

  • Son,Myeong-Hwan;Lee,Gi-Yeong;Baek,Seung-Uk
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.1
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    • pp.1-8
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    • 2002
  • The effects of sideslip on the vortex over a delta wing was investigated experimentallu at a free strean velocity of 40 m/sec, corresponding to a Reynolds number of 1.76$\times$$10^6$, based on the root chord. The angles of attack ranged from $16{^{\circ}}$ to $28{^{\circ}}$, and the sideslip angles treated were $0{^{\circ}}$, $-10{^{\circ}}$, and $-20{^{\circ}}$. It was observed that the sideslip decreased the strengths of the vortices of both windward and leeward sides of the wing, and promoted the vortex breakdown on the windward side. At sideslip angle of $-10{^{\circ}}$, the vortex strength of leeward side was increased as the angle of attack increased. This asymmetric development and breakdown of vortices in sideslip condition would cause an abrubt change of the rolling moment at a high angle of of attack, which could be considered as a rolling moment instability.