• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2498-2503
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• 2023

When the reactor vessel is penetrated in a severe accident of light water reactor, the molten fuel-coolant interaction including the jet breakup occurs and the jet breakup length becomes one of the important parameters. Most numerical studies on jet breakup process have been carried out using dedicated computer codes. Some researchers are trying to apply commercial CFD codes to their investigations on comprehensive jet breakup process. However, the complexity of the phenomena limits the CFD application only to hydrodynamic aspects. In the present study, numerical analysis of jet breakup under vapor generation is pursued using the STAR-CCM + code. The obtained CFD prediction of the MATE09 experiment shows jet breakup progression patterns consistent to the images taken in the experiment. Further, the predicted positions of leading head, which determine the jet breakup length, are in good agreement with the MATE 09 data. The investigation of hydrodynamic effects on the jet breakup with higher jet velocity results in a stronger shear force and earlier jet breakup process even though there exists the vapor pocket around the corium jet. In future studies, the effect of vapor intensity on the jet breakup length would be investigated further by changing other parameters.

• 한국전산유체공학회지
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• 제10권1호
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• pp.39-44
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• 2005

The numerical investigation of the interaction between the underexpanded supersonic jet and the perpendicular plate is carried out using the TVD numerical method. The wave structure in the flowfield and the pressure and temperature distributions on the plate surface are obtained by the numerical analysis. Especially, the influence of self-induced flow oscillation caused by the impinging jet and the characteristic of impinging jet are shown. From the result of the numerical analysis, it is concluded that the pressure and the temperature fluctuations on the plate surface strongly depends on the pressure ratio in the flowfield and the position of plate.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.120-125
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• 2003

Recently, lateral jet has been adopted as an effective control device for high maneuverable tactical missiles in supersonic regime. Aerodynamic interference caused by the lateral jet can be categorized into two phenomena : local interaction redistributing surface pressure near the jet exit region and downstream interaction affecting tail control effectiveness. As part of on-going research, this paper deals with the aerodynamic modeling to predict the variation of force and moment when lateral jet of is activated on the missile body. For this purpose, a series of numerical simulation has been performed and the results are presented. Using the information obtained by CFD, aerodynamic model of preliminary level has been constructed and is reviewed. Some relevant comparison with wind tunnel tests are presented.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1330-1337
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• 2016

A visualization test of the fuel-coolant interaction in the Test for Real cOrium Interaction with water (TROI) test facility was carried out. To experimentally simulate the In-Vessel corium Retention (IVR)- External Reactor Vessel Cooling (ERVC) conditions, prototypic corium was released directly into the coolant water without a free fall in a gas phase before making contact with the coolant. Corium (34.39 kg) consisting of uranium oxide and zirconium oxide with a weight ratio of 8:2 was superheated, and 22.54 kg of the 34.39 kg corium was passed through water contained in a transparent interaction vessel. An image of the corium jet behavior in the coolant was taken by a high-speed camera every millisecond. Thermocouple junctions installed in the vertical direction of the coolant were cut sequentially by the falling corium jet. It was clearly observed that the visualization image of the corium jet taken during the fuel-coolant interaction corresponded with the temperature variations in the direction of the falling melt. The corium penetrated through the coolant, and the jet leading edge velocity was 2.0 m/s. Debris smaller than 1 mm was 15% of the total weight of the debris collected after a fuel-coolant interaction test, and the mass median diameter was 2.9 mm.

• 대한기계학회논문집B
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• 제25권8호
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• pp.1087-1096
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• 2001

The dynamic structures of unsteady CH$_4$/Air jet diffusion flame with a flame-vortex interaction were numerically investigated. A timed-dependent, axisymmetric computational model and a low mach number approximation were employed in the present calculation. A two-step global reaction mechanism which considers 6 species, was used to calculate the reaction rates. The predicted results including the gravitational effect show that the large outer vortices and the small inner vortices can be well simulated without any additional disturbances near nozzle tip. It was found that the temperature and species concentrations have deviated values even for the same mixture fraction in the flame-vortex interaction region. It was also shown that the flame surface is not deformed by the inner vortex in upstream region, while in downstream region, the flame surface is compressed or stretched by the outer vortex roll-up. The present unsteady jet flame configuration accompanying a flame-vortex interaction is expected to give good implications for the unsteady structures of turbulent flames.

• 대한기계학회논문집B
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• 제29권6호
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• pp.730-736
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• 2005

It has been reported that the interacting multiple jet flames of propane fuel are not extinguished even at the choking velocity at the nozzle exit if eight small nozzles are arranged along the imaginary circle of $40{\sim}72$ times the diameter of single nozzle. In this research, experiments were conducted to know the NO and CO emission characteristics of the interacting flames. Measurements along the centerline of the flame revealed that decrease in CO concentration was followed by the NO decrease and $O_2$ increase. It was found that interacting flame emitted less NO than that of similar area single jet flame. Also, NO emission of partially premixed interacting flame was decreased up to $17\%$ of that of non-premixed multiple jet flame. Though the mechanism of the NO reduction was not clear from this experiment, it's been shown that partially premixed multiple jet flames could be used to achieve clean and highly stable combustion.

• 한국항공우주학회지
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• 제33권3호
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• pp.1-9
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• 2005

본 논문에서는 직접모사법을 이용하여 고 고도 희박 영역에서 로켓의 자세 제어에 필수적인 측면 제트 분사와 그에 따른 자유 흐름 유동과 측면 제트의 상호 작용에 대한 연구를 수행하였다. 밀도 차가 큰 자유 흐름 유동과 제트 유동을 동시에 모사하기 위해 입자 가중치 기법을 사용하였다. 두 수직한 평판 사이의 유동 및 측면 제트 분사에 의한 상호 작용 해석을 수행하였고 그 결과를 실험치와 비교하여 프로그램을 검증하였다. 좀 더 실제적인 로켓 모델로 blunted cone cylinder 형상에 대하여 받음각을 변화시켜가며 자유 흐름 유동과 측면 제트의 상호 작용에 대한 연구를 수행하였다. 표면 압력 차이의 분포를 기준으로 람다(lambda) 충격파와 후류의 영향을 토의하였다. 받음각이 있는 유동의 경우 leeward 방향으로는 제트와 자유 흐름 유동의 상호 작용이 약해지며, windward 방향으로는 상호 작용이 매우 강해지는 것을 확인할 수 있었다.

• 한국해양공학회지
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• 제35권6호
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• pp.403-413
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• 2021

As the size of ships increases, the size and output power of their thrusters also increase. When a large ship berths or unberths, the jet flow produced from its thruster has an adverse effect on the stability of quay walls. In this study, we conducted a numerical analysis to examine the impact of the thruster jet flow of a 30,000 TEU container ship, which is expected to be built in the near future, on the stability of a quay wall. In the numerical simulation, we used the fluid-structure interaction analysis technique of LS-DYNA, which is calculated by the overlapping capability using an arbitrary Lagrangian Eulerian formulation and Euler-Lagrange coupling algorithm with an explicit finite element method. As the ship approached the quay wall and the vertical position of the thruster approached the mound of the quay wall, the jet flow directly affected the foot-protection blocks and armor stones. The movement and separation of the foot-protection blocks and armor stones were confirmed in the area affected directly by the thruster jet flow of the container ship. Therefore, the thruster jet flows of ultra-large ships must be considered when planning and designing ports. In addition, the stability of existing port structures must be evaluated.

• 한국군사과학기술학회지
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• 제6권4호
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• pp.124-131
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• 2003

When a secondary gaseous flow is injected vertically into a supersonic flow through circular nozzle, a complicated structure of flow field is produced around the injection area. The interaction between the two streams produces a strong bow shock wane on the upstream side of the side-jet. The results show that bow shock wave and turbulent boundary layer interaction induces the boundary layer separation in front of the side-jet. This study is to analyze the structure of flow fields and distribution of surface pressure on the flat plate according to total pressure ratio using a supersonic cold-flow system and also to study the control force of affected side-jet. The nozzle of main flow was designed to have Mach 2.88 at the exit. The injector has a sonic nozzle with 4mm diameter at the exit of the side-jet. In experiments, The oil flow visualization using a silicone oil and ink was conducted in order to analyze the structure of flow fields around the side-jet. The flow fields are visualized using the schlieren method. In this study, a computational fluid dynamic solution is also compared with experimental results.

• 한국항공우주학회지
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• 제32권4호
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• pp.73-79
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• 2004

초음속 유동하에서 측 추력기의 후방에 램프를 설치하였을 경우의 유통 현상을 실험 및 수치해석을 이용하여 해석하였다. 실험적인 방법으로, 가시화방법으로는 쉴리렌, 압력 측정을 위한 방법으로 압력 탭 (Pressure Tap), Pressure Sensitive Paint를 이용하였으며, 수치해석을 위하여 AeroSoft사의 GASP ver. 4.0을 사용하였다. 실험조건은 자유류의 흐름이 마하수 4 측 추력기와 자유류의 압력비가 532 이었으며 GASP을 사용하여 3D 램프형상에 대한 고찰을 하였다. 위의 모든 결과들은 후방의 램프가 없을 경우와 비교를 통하여 램프를 장착하였을 경우 수직력의 감소없이 피칭다운 모멘트가 70% 정도 감소함을 확인하였다.