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Numerical Analysis of a Liquid Sheet Flow around a Simplified Sprinkler Head Using a CFD Model (CFD 모델을 이용한 단순 스프링클러 헤드 주위의 액막 유동해석)

  • Kim, Sung-Chan
    • Fire Science and Engineering
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    • v.30 no.6
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    • pp.111-117
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    • 2016
  • The present study examined the free surface flow of a liquid sheet near a sprinkler head using a Computational Fluid Dynamics (CFD) model and considered the feasibility of the empirical model for predicting the initial spray characteristics of the sprinkler head through a comparison of the CFD results. The CFD calculation for a simplified sprinkler geometry considering the nozzle and deflector were performed using the commercially available CFD package, CFX 14.0 with the standard kε turbulence model and theVolume of Fluid (VOF) method. The predicted velocity of the empirical model at the edge of deflector were in good agreement with that of the CFD model for the flat plate region but there was a certain discrepancy between the two models for the complex geometry region. The mean droplet diameter predicted by the empirical model differed significantly from the measured value of the real sprinkler head. On the other hand, the empirical model can be used to understand the mechanism of droplet formation near the sprinkler head and predict the initial spray characteristics for cases without experimental data.

Restoring Characteristics of Windy Leisure Boat Associated to Sailing Angle of Attack and Effet of Side Force (풍력 레저선박의 돛 받음각과 횡력에 대한 복원력 특성)

  • Kang, Gyung Ju;Moon, Byung Young
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.1
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    • pp.13-18
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    • 2015
  • Characteristics of restoring force for the wind-powered leisure boat was investigated using mathematical formulation and commercial computational method such as the ANSYS Workbench CFX-Mesh. The objective is to find the restoring moment and heel moment while boat is sailing in windy power. Conditions for angle of attack were given from 5 to 90. It is known that side force is larger in terms of angle of attack is higher, however critical angle is suggested to limit before over of 60 for safe navigation for boat in wind. Natural results are found that stronger heel moment is observed when sail is used than no sail, and higher angle of attack is induced stronger heel moment.

Numerical Analysis of Internal Flow Distribution in Scale-Down APR+ (축소 APR+ 원자로 모형에서의 내부유동분포 수치해석)

  • Lee, Gong Hee;Bang, Young Seok;Woo, Sweng Woong;Kim, Do Hyeong;Kang, Min Gu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.9
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    • pp.855-862
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    • 2013
  • A series of 1/5 scale-down reactor flow distribution tests had been conducted to determine the hydraulic characteristics of an APR+ (Advanced Power Reactor Plus), which were used as the input data for an open core thermal margin analysis code. In this study, to examine the applicability of computational fluid dynamics with the porous model to the analysis of APR+ internal flow, simulations were conducted using the commercial multi-purpose computational fluid dynamics software ANSYS CFX V.14. It was concluded that the porous domain approach for some reactor internal structures could adequately predict the flow characteristics inside a reactor in a qualitative manner. If sufficient computational resources are available, the predicted core inlet flow distribution is expected to be more accurate by considering the real geometry of the internal structures, especially upstream of the core inlet.

Wind Load Analysis of 61ton-class Container Crane using the Computation Fluid Dynamics (61ton 컨테이너 크레인의 전산유동해석을 통한 풍하중 분석)

  • Lee, Su-Hong;Lee, Seong-Wook;Han, Dong-Seop;Kim, Tae-Hyung;Han, Geun-Jo
    • Journal of Navigation and Port Research
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    • v.32 no.3
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    • pp.251-255
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    • 2008
  • Container cranes are vulnerable structure about difficult weather conditions bemuse there is no shielding facility to protect them from the strong wind. This study was carried out to analyze the wind load which have an effect on container crane according to the various wind direction. The container crane is a model of a 61-ton class that used broadly in the current ports. The external fluid field was figured as a cylinder which was set up 500m×200m. In this study, we applied mean wind load conformed to 'Design Criteria of Wind Load' in 'Load Criteria of Building Structures' and an external fluid field was divided as interval of 10 degrees to analyze effect according to a wind direction In this conditions, we carried out the computation fluid dynamic analysis using the CFX-10. As we compared computation fluid dynamic analysis with wind tunnel test, we analyzed the wind load which was needed to design the container crane.

Shape Optimization of Impeller Blades for Bidirectional Axial Flow Pump (양방향 축류펌프용 임펠러 블레이드의 형상최적설계)

  • Baek, Seok Heum;Jung, Won Hyuk;Kang, Sangmo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.12
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    • pp.1141-1150
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    • 2012
  • This paper describes the shape optimization of impeller blades for an anti-heeling bidirectional axial flow pump used in ships. In general, a bidirectional axial pump has efficiency much lower than that of a classical unidirectional pump because of the symmetry of the blade type. In this study, by focusing on a pump impeller, the shape of the blades is redesigned to develop a bidirectional axial pump with higher efficiency. The commercial code employed in this simulation is CFX v.13. The CFD result of the pump torque, head, and hydraulic efficiency was compared. The orthogonal array (OA) and analysis of variance (ANOVA) techniques and surrogate-model-based optimization using orthogonal polynomials are employed to determine the main effects and their optimal design variables. According to the optimal design, we confirm an effective design variable for impeller blades and explain the optimal solution as well as the usefulness of satisfying the constraints of the pump torque and head.

Effects of Impeller Shape of Submersible Nonclogging Pump on its Performance (비 막힘형 수중 펌프 임펠러 형상이 펌프 성능에 미치는 영향)

  • Yun, Jeong-Eui
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.12
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    • pp.1201-1207
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    • 2012
  • This study was performed to develop a high-efficiency submersible nonclogging pump impeller. Toward this end, we simulated the effect of some parameters such as the outlet position of a blade (hI), outlet width of a blade (b2), and hub profile on the pump efficiency by using the commercial codes ANSYS CFX and BladeGen. The results showed that the pump efficiency was proportional up to hI= 38 mm and b2= 55 mm. It remained constant over these values. However, the head and shaft power were proportional to hI and b2 in the simulated ranges. The effects of hub profile changes on the pump efficiency were relatively small compared to those of the other parameters.

Lightweight Design of a Main Starting Air Valve through FSI Analysis (구조연성해석을 통한 메인스타팅 에어밸브의 경량화설계)

  • Lee, Kwon-Hee;Jang, Byung-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.11
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    • pp.5371-5376
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    • 2013
  • The role of a main starting air valve is to supply compressed air to the diesel engine for starting the stopped diesel engine of a ship and cut off the air during normal operation. In this study, the main starting air valve with 80mm size was designed based on the developed valve with 50mm size. The concept design of the 80A main starting air valve was completed by using CATIA. Then, fluid analysis was performed to investigate the flow characteristics such as pressure and velocity distribution. Sequentially, structural analysis using FSI was performed. In this study, ANSYS CFX and ANSYS Workbench are utilized. The heavy weight of the body can deteriorate the strength performance of neighbor elements, leading to undesirable effect on flow characteristics. Thus, in this research, a lightweight design of the body was suggested satisfying strength requirement. The weight of the suggested design was reduced by 7kg, and the strength satisfied its requirement.

Blowdown Prediction of Safety Relief Valve and FSI Analysis (안전릴리프밸브의 블로우 다운 예측 및 유체-구조 연성해석)

  • Choi, Ji-Won;Jang, Si-Hwan;Lee, Kwon-Hee
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.12
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    • pp.729-734
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    • 2017
  • A safety relief valve is a device that relieves excessive pressure in piping lines or tanks and maintains pressure at the appropriate pressure level for use. The (pressure in the) safety valve is directly influenced by the change in the back pressure, depending on whether the vents in the spring bonnet are vented to the atmosphere or to the outlet. The back pressure is divided into the built-up back pressure and the superimposed back pressure, and the back pressure characteristics vary according to the usage conditions. The safety valve used in this study is a Conventional Safety Relief Valve. The blowdown of the safety valve is predicted by establishing the equilibrium equation between the opening force and spring force considering the back pressure characteristics. Its reliability is secured by using CFX17.1. In addition, the safety of the safety valve trim was examined through fluid-structure interaction analysis.

Arrangement Design and Performance Evaluation for Multiple Wind Turbines of 10MW Class Floating Wave-Offshore Wind Hybrid Power Generation System (10MW급 부유식 파력-해상풍력 연계형 발전 시스템의 다수 풍력터빈 배치 설계 및 성능 평가)

  • Park, Sewan;Kim, Kyong-Hwan;Lee, Kang-Su;Park, Yeon-Seok;Oh, Hyunseok;Shin, Hyungki;Hong, Keyyong
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.18 no.2
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    • pp.123-132
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    • 2015
  • In this study, an arrangement design process for multiple wind turbines, placed on the 10MW class floating wave-offshore wind hybrid power generation system, was presented, and the aerodynamic performance was evaluated by using a computational fluid dynamics. An arrangement design, which produces a maximum power in the site wind field, was found by using a commercial program, WindPRO, based on a blade element momentum theory, then the effect of wake interference on the system between multiple wind turbines was studied and evaluated by using ANSYS CFX.

Numerical Study on the Side-Wind Aerodynamic Forces of Chambered 3-D Thin-Plate Rigid-Body Model (캠버가 있는 3차원 박판 강체 모형의 측풍 공기력에 대한 수치 연구)

  • Shin, Jong-Hyeon;Chang, Se-Myong;Moon, Byung-Young
    • 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.