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Original Article
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NUMERICAL ANALYSIS OF BUBBLE COLLAPSE ATTACHED TO WALL WITH STAND-OFF DISTANCE
이격 거리에 따른 벽면부착 버블 붕괴의 전산수치해석
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C.G. Kang, T.H. Phan, V.T. Nguyen, W.G. Park
강정구, 판 탄호앙, 응 웬반투, 박원규
- Cavitation occurs due to the reduction of local pressure in a liquid to below its vapor pressure, leading to vaporization. This process …
- Cavitation occurs due to the reduction of local pressure in a liquid to below its vapor pressure, leading to vaporization. This process finds applications across a broad spectrum of fields, from mechanical engineering domains to biomedical engineering, alcohol fermentation, soil improvement, and bacteria sterilization. This study aims to deepen the understanding of the dynamics of micro jet during the bubble collapse attached to wall. It particularly focuses on the bubble formation and collapse processes induced by High-Intensity Focused Ultrasound (HIFU). Numerical analysis using an in-house code validated across various conditions in previous studies was conducted. Advanced numerical methodologies, including the Navier-Stokes equation based Homogeneous Mixture Model, were applied to the numerical analysis. This study successfully delineates the shape characteristics and the pressure increasing during bubble collapse, providing insights into the physical processes in non-invasive medical treatments through HIFU. This foundational research contributes to a deeper understanding of cavitation phenomena and its mechanical as well as biomedical applications. - COLLAPSE
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NUMERICAL ANALYSIS OF BUBBLE COLLAPSE ATTACHED TO WALL WITH STAND-OFF DISTANCE
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Original Article
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BOUNDARY LAYER TRANSITION MODEL WITH COMPRESSIBILITY CORRECTION FOR TRANSONIC FLOW SIMULATIONS
압축성 효과 보정을 적용한 경계층 천이 모델의 천음속 유동해석
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J.B. Hong, Y.S. Jung
홍지범, 정용수
- The Medida-Baeder laminar-turbulent boundary layer transition model, based on Reynolds-averaged Navier-Stokes, has been extended by applying an existing compressibility correction. The correction …
- The Medida-Baeder laminar-turbulent boundary layer transition model, based on Reynolds-averaged Navier-Stokes, has been extended by applying an existing compressibility correction. The correction was derived from the stability analysis of Tollmien-Schlichting instabilities and developed for the Langty-Menter transition model. Performance of the extended model was evaluated through the transonic flows over VA-2 and CAST10-2 airfoils where the compressible effects prevail. With the extended model, the prediction of transition onset is delayed, resulting in improved agreement with experimental data from the baseline model in skin friction distribution. Furthermore, the extended model was applied to the challenging NASA Common Research Model-Natural Laminar Flow wing-body configuration under transonic flight conditions. Sectional pressure coefficients and transition locations were compared with experimental results at various angles of attack. The prediction accuracy in transition onset along the wing span is improved, which are comparable with the predicting result from linear stability theory based transition model. - COLLAPSE
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BOUNDARY LAYER TRANSITION MODEL WITH COMPRESSIBILITY CORRECTION FOR TRANSONIC FLOW SIMULATIONS
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Original Article
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A STUDY ON CHARACTERISTICS OF VLS GAS MANAGEMENT SYSTEM USING CFD
CFD를 활용한 수직발사대 화염처리장치 성능 특성 연구
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Y.J. Jang, N. Lee, H. Ku, J. Oh
장유진, 이남훈, 구현곤, 오재이
- Vertical Launching System(VLS) is an equipment that carries a large number of guided missiles and launches missiles vertically from a warship in …
- Vertical Launching System(VLS) is an equipment that carries a large number of guided missiles and launches missiles vertically from a warship in case of emergency. Korean Vertical Launching System(KVLS) adopts Hot launching method that rocket motor ignites inside the launcher, causing flames to gather within structures such as canister, plenum, uptake, and etc. In this launching method, the high-temperature and high-pressure flames from missiles affect the launching system and the adjacent hull structures, so a lot of research on its structure and heat resistance is required. To do that, it is important to understand the flow characteristics of the flame in the launcher system. In this study, a CFD analysis is performed in two cases where the missile is fired normally and restrained due to abnormal behavior. For the numerical simulation, a two-dimensional Reynolds-averaged Navier-Stokes(RANS) solver is adopted. An overset grid method is applied to simulate the dynamic behavior of a missile for normal launch case. A transient pressure response on the wall inside and outside of KVLS is suggested to understand the flow-field inside the launching system. - COLLAPSE
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A STUDY ON CHARACTERISTICS OF VLS GAS MANAGEMENT SYSTEM USING CFD
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Original Article
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NUMERICAL INVESTIGATION OF AERODYNAMIC INTERACTION OF WINGTIP-MOUNTED TRACTOR PROPELLER WITH FIXED WING
날개 끝단 부착 프로펠러와 날개 간의 공기역학적 상호작용 효과에 대한 전산해석
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H.S. Song, Y.H. Hwang, S.J. Kim, R.S. Myong, Y.S. Jung, H. Lee
송현수, 황유현, 김시진, 명노신, 정용수, 이학진
- The next-generation sustainable aircraft using distributed electric propulsion (DEP) system has gained significant attention to replace conventional aircraft. Although the DEP system …
- The next-generation sustainable aircraft using distributed electric propulsion (DEP) system has gained significant attention to replace conventional aircraft. Although the DEP system helps improve flight safety, reduce environmental noise, and achieve redundancy in the propulsion system, the mutual interaction between the multiple propeller and fixed-wing occurs more frequently. This interactional phenomenon is a dominant factor affecting the aerodynamic performance of vehicles. This study investigates the aerodynamic interactions between wing-tip mounted tractor propeller and fixed-wing using the lattice-Boltzmann method (LBM). NASA's Workshop for Integrated Propeller Prediction (WIPP) model is considered, and the LBM predictions are compared against the experimental data for validation. The propeller wake effects on the wing aerodynamics and flow field are discussed depending on the wing angles of attack. - COLLAPSE
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NUMERICAL INVESTIGATION OF AERODYNAMIC INTERACTION OF WINGTIP-MOUNTED TRACTOR PROPELLER WITH FIXED WING
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Original Article
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ANALYSIS OF THE UNSTEADY REYNOLDSAVERAGED SIMULATION TECHNIQUE FOR RAYLEIGH-BéNARD CONVECTION
레일리-버나드 대류에 대한 비정상 레이놀즈평균 모사 기법의 분석
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D.-S. Joo, D. You
주다솔, 유동현
- This study investigates the capability of unsteady Reynolds-averaged Navier-Stokes(URANS) simulations in predicting turbulent Rayleigh-Bénard convection, with a particular focus on the prediction …
- This study investigates the capability of unsteady Reynolds-averaged Navier-Stokes(URANS) simulations in predicting turbulent Rayleigh-Bénard convection, with a particular focus on the prediction of convective cells and turbulent heat transfer. Previous researchers have posited that URANS can accurately simulate convective rolls, which in turn may enable reliable predictions of heat transfer in turbulent regimes. The analysis distinguishes between the effects modeled and resolved by URANS—the latter capturing the unsteady fluid motions’ contributions to heat transport. By simplifying the RANS model equations, the study estimates the turbulence diffusivities for momentum and heat, and derives scaling relationships for the Rayleigh, Prandtl, and Nusselt numbers that demonstrate the influence of large-scale convection cells. This approach qualitatively explains previous observations on the diminishing modeled effects on heat flux at higher Rayleigh numbers as observed in prior studies by Kenjereš and Hanjalić [2006, Int. J. Heat. Fluid. Fl., Vol. 27, No.5.]. Additionally, the study estimates the velocity scale of convective cells predicted by URANS, factoring in the modeled turbulent viscosity and thermal diffusivity alongside Rayleigh and Prandtl numbers. Findings suggest that the velocity scale, consistent across various turbulence models, can be approximated using the free-fall velocity concept, irrespective of the modeled turbulent viscosity. - COLLAPSE
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ANALYSIS OF THE UNSTEADY REYNOLDSAVERAGED SIMULATION TECHNIQUE FOR RAYLEIGH-BéNARD CONVECTION
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Original Article
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OPTIMAL YAW CONTROL OF A WIND FARM BASED ON COMPUTATIONAL FLUID DYNAMICS
전산유체역학 해석을 기반으로 한 풍력단지의 최적 요 제어
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T. Kim, J. Song, D. You
김태완, 송정환, 유동현
- Energy production can be increased by active yaw control of wind turbines. Active yaw control can deflect the wake region of an …
- Energy production can be increased by active yaw control of wind turbines. Active yaw control can deflect the wake region of an upstream wind turbine, increasing the mean wind speed passing through a downstream wind turbine. Conventional optimization of active yaw control maximizes the power generation based on a yawed wake model. However, a yawed wake model cannot predict the blockage effect of a wind farm and the spanwise velocity in the deflected wake region. In the present study, optimal yaw control based on a yawed wake model is shown to be suboptimal in a real-world wind farm by Reynolds-averaged Navier-Stokes simulations. Considering both the streamwise and the spanwise velocity fields in a wind farm, conventional yaw control is improved to maximize the generated power. - COLLAPSE
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OPTIMAL YAW CONTROL OF A WIND FARM BASED ON COMPUTATIONAL FLUID DYNAMICS
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Original Article
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ANALYZING PROPELLER PERFORMANCE IN ICING CONDITIONS USING NUMERICAL SIMULATION METHODS
수치해석을 이용한 결빙 조건에서의 프로펠러 성능 분석
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Y. Kim, K. Yee
김용환, 이관중
- This study predicts the icing phenomenon on the propellers of electric propulsion aircraft and analyses the resulting efficiency reduction. Aircraft icing is …
- This study predicts the icing phenomenon on the propellers of electric propulsion aircraft and analyses the resulting efficiency reduction. Aircraft icing is mainly divided into rime ice and glaze ice, each of which has different icing conditions and morphological characteristics. Rime ice occurs at low temperatures, where droplets freeze immediately on the surface, forming opaque ice, while glaze ice occurs at relatively high temperatures, where droplets freeze as they flow along the surface, forming transparent ice. Due to their high speeds and short chord lengths, propellers are particularly vulnerable to icing. In this study, we compared 2D and 3D icing prediction methods using ICEPAC, an existing icing prediction code, and verified the reliability of the results with experimental data. Furthermore, we analysed the reduction in propeller efficiency based on the predicted changes in icing geometry and evaluated the impact of icing conditions using the Kriging method. The analysis confirmed the vulnerability of the propeller to icing conditions, particularly the effect of increased torque on the propeller due to icing on efficiency. Ultimately, it was determined that in regions with an LWC of 0.2 g/m³ or less, the propeller efficiency was over 25% of its original efficiency, with significant reductions observed in most other areas. - COLLAPSE
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ANALYZING PROPELLER PERFORMANCE IN ICING CONDITIONS USING NUMERICAL SIMULATION METHODS
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Original Article
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A STUDY ON THE EFFECTS OF ISOLATION-HEAT PAINT ON THE TEMPERATURE CHARACTERISTICS OF A CONTINUOUS WELDED RAIL
차열도료가 장대레일 온도 특성에 미치는 영향에 대한 고찰
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Y.S. Park, W.S. Jeong, H.J. Kim, N.H. Lim
박윤수, 정우석, 김홍집, 임남형
- In summer, the rail temperature rises by the high degree of solar radiation, which causes crucial problems such as derailment due to …
- In summer, the rail temperature rises by the high degree of solar radiation, which causes crucial problems such as derailment due to the buckling of the rail. This study deals with quantifying the effect of the isolation-heat paint with high reflectivity by analyzing the temperature characteristics of the continuous welded rail. From the results of numerical analysis, the solar heat flux and resultant temperature of painted rail are significantly reduced compared to those without the paint. In addition, the influence of rail installation orientation on its temperature characteristics is markedly decreased due to the high reflectivity of isolation-heat paint. - COLLAPSE
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A STUDY ON THE EFFECTS OF ISOLATION-HEAT PAINT ON THE TEMPERATURE CHARACTERISTICS OF A CONTINUOUS WELDED RAIL
Journal Informaiton
Journal of Computational Fluids Engineering
Journal of Computational Fluids Engineering
