• Journal of the Korean Society for Railway
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• v.9 no.5 s.36
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• pp.511-516
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• 2006

A standard framework of CFD(Computational Fluid dynamics) analysis for railway system has been developed to evaluate the overall aerodynamic performance of railway system and has been adopted to numerical simulation of the pressure field around KTX train. The framework is composed of standard aerodynamic model and standard aerodynamic performance to customize the general CFD solution process reflecting the characteristics of railway system such as various operation mode and performance factors. The results show that the standard framework of CFD analysis for railway system can provide objectivity and consistency to the CFD analysis for railway system and the pressure field around KTX train has been successively solved.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.223-227
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• 2005

최근 전산 유체의 발달로 이상 유동해석의 캐비테이션 모델 적용 방법이 발전되어 왔으나 다양한 수력학적 시스템에서 발생하는 캐비테이션 유동은 난류이며 물과 공기 사이에서의 복잡한 상호 작용을 가지고 있으므로 그 적용 예가 아직은 미흡한 상태이다. 본 연구에서는 수중에서의 캐비테이션 해석과 이상 유동 해석을 위한 코드 개발 및 검증을 목적으로 3차원 회전체 주위의 캐비테이션 유동을 여러 가지 조건들의 변화를 적용하여 해석하였다. 또한 캐비테이션 발생과 관련한 다른 난류 모델에 적용하여 비교 분석을 수행하였다. 해석을 위한 모델의 지배방정식은 이상유동 Wavier-Stokes 방정식, 질량$\cdot$모멘텀 방정식의 혼합된 형태로 구성되어 있으며 방정식의 해를 구하기 위한 방법으로 유한차분법을 이용하였다. 해석결과의 신뢰성을 고려하여 반구형 실린더 주위의 캐비테이션 유동의 실험치와 비교 분석하였다. 그 결과, 본 연구의 수치 해석 방법과 실험적 방법의 결과가 강한 양의 상관관계를 가짐을 알 수 있었으며, 이러한 수치적 뒷받침은 본 연구의 전산수치 해석 방법이 앞으로의 여러 유동 해석으로의 적용 가능성을 보여준다.

• Journal of the Korean Society for Railway
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• v.16 no.3
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• pp.169-174
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• 2013

The effect of modifying the shape of a high-performance EMU train on the aerodynamic drag is studied here using Computational Fluid Dynamics(CFD) based on three dimensional Steady-state Navier-Stokes equation and two equation turbulence modeling. FLUENT 12 and Gambit 2.4.6 are employed for a numerical simulation of the aerodynamic drag of a streamlined-shape train as well as a proto type train. The characteristics of the aerodynamic drag of trains in tunnels are analyzed in a comparison with these characteristics in an open space. The contribution of the aerodynamic drag of each case is also investigated to establish principal pertaining to drag reduction for urban trains in tunnels. The aerodynamic drag of a streamlined train was reduced to 9.8% relative to a proto-type train with a blunt nose and a protruding roof facility and underbody shape: the running resistance is expected to be reduced by as much as 4% at a running speed of 80km/h.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.6
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• pp.9-16
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• 2010

The SFRJ(Solid Fuel Ram-Jet) propulsion is attractive for projectiles because of the combination of high propulsive performance and low system complexity more than conventional projectiles. The Objective of this research was to characterize the inlet aerodynamic characteristics (center-body & pitot type) in SFRJ. Diffuser static pressure & combustion chamber pressure was tested and the AoA was changed $0^{\circ}$ and $4^{\circ}$ at Mach number of 3.0 for performance estimate. The performance study of inlet was carried out with the Schlieren system and Supersonic cold-flow system. Under mach 3.0, the center-body showed twice higher total pressure recovering ratio than the pitot type. A Computational fluid dynamic solution is applied internal flow of inlet and the solutions are compared with experimental results.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.545-552
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• 2009

The marine medium-speed diesel engines are operated by two methods; one is the electric motors, and the other air starting motors. Even though air starting motor is dependent of the engine types and sizes, it has been widely used in this area due to its simplicity, convenience and reliability. However most of them are currently imported from overseas due to the lack of the cutting-edge technology in terms of design and manufacturing. Therefore, from the point of this view, the air starting motor needs to be produced by our own techniques. The purpose of this paper is to give the designing parameters in order to make a proper "Air Starting Motor" using CFD. The aerodynamic approaches were given to understand the internal flow characteristics of the air starting motor. In addition, we have carried out the effects of tip clearance. In the calculations the tip clearance of air starting motor has been varied between 0% and 5.7% of blade span.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.132-138
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• 2003

The optimal design for a leading car considering the aerodynamic resistance is required on the high-speed train due to increasing of ratio of drag force with proportion for the square of velocity. The aerodynamic analysis using CFD in the stage of concept design offers more economical analysis method which is used to estimate the influence of flow and pressure around the leading car than the experimental method using the Mock-up. In this study, we want to assist the artistic design with aerodynamics analysis in order to get the optimal design for leading car with the operation speed of 180km/h. The results of aerodynamic analysis for two leading car models which one is expressed with lineal beauty and the other is with curvaceous beauty are compared with each other and they offer the proposal of modification for two models in order to decrease the drag force. The shape of curvaceous model is better for the pressure force but slightly worse for the viscous force than the other. The Fluent software is used for the calculation of flow profile in this study.

• Journal of the Korean Society for Railway
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• v.13 no.4
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• pp.371-375
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• 2010

In order to decide the strength requirement of the window glass for the high-speed train, the pressure change during the passage of the EMU type high-speed train has been numerically simulated. Based on the calculation results, the pressure difference between the inner and outer pressure of the cabin has been calculated to yield the amount of load acting on the window glass of the cabin. To simulate the pressure field generated by the high-speed train passing through the tunnel, computational fluid dynamics based on the axi-symmetric Navier-Stokes equation has been employed. The pressure change inside a train has been calculated using first order difference approximation based on a linear equation between the pressure change ratio inside a train and the pressure difference of inside and outside of the train.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.211-219
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• 2017

In this study, we performed numerical simulations on a circulating air classifier using a commercial computational fluid dynamics program. The variations in the grade efficiency, the cut-size and the cut-sharpness were calculated and discussed. By controlling the rotating speed of the main fan, the cut-size could be rapidly increased. However the linearity of the cut-size variation with respect to the main fan speed was not sufficient for application to contaminated soil classification processes. On the other hand, by varying the rotating speed of the classifying fan, the cut-size gradually decreased and could be precisely adjusted. Using both the main fan and the classifying fan, we could achieve larger cut-sharpness values and better classifying performances.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.97-108
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• 2015

In the design of sailing yachts, para-glider, or high-sky wind power, etc., the analysis of side-wind aerodynamic forces exerted on a cambered 3-D model is very important to predict the performance of various machinery systems. To understand the essential flow physics around the three-dimensional shape, simplified rigid-body models are proposed in this study. Four parameters such as free stream velocity, angle of attack, aspect ratio, and camber are considered as the independent variables. Lift and drag coefficients are computed with CFD technique using ANSYS-CFX, and the results with the visualization of post-processed flow fields are analyzed in the viewpoint of fluid dynamics.

• Clean Technology
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• v.18 no.4
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• pp.410-418
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• 2012

The performance of the ammonia injection gun (AIG) used for maximizing the utilization of reducing agent in the selective catalytic reduction (SCR) system is decided by several parameters such as the pattern of flow distribution, geometry of the air distribution manifold (ADM) and the array and geometry of nozzles. In the study, the uniformity of jet flows from the nozzles in AIG was analyzed statistically by using the computational fluid dynamics (CFD) method to evaluate the role of design parameters on the performance of the SCR system. The uniformity of jet flows from the nozzles is being deteriorated with increasing the supplying flow rate to the AIG. Distribution rates to each branch pipe become lower with decreasing distance to the header, and flow rates from nozzle are also reduced with decreasing distance to the header. The uniformity of jet flows from nozzles becomes stable significantly when the ratio of summative area of nozzles to each sectional area of the branch pipe is below 0.5.