• International Journal of Safety
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• 제5권2호
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• pp.29-33
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• 2006

A numerical flow analysis of the case of a refrigeration warehouse where an unusual death of an operator occurred by deficiency of oxygen is performed by using STAR-CD program of the computational fluid dynamics (CFD) code. The refrigeration room of the warehouse for storing the fruits maintains an atmosphere of 95% nitrogen and 5% oxygen by volume. When the operator was found dead in the refrigeration room, the room was in normal operating conditions except for the fact that the auxiliary door had been left open. For the flow analysis, unsteady 3-dimensional natural convection with mass transfer is considered. The flow analysis result is compared with the oxygen concentration level measured against time during on-site investigation. The change in oxygen concentration level in the warehouse due to the opening of the auxiliary door is found to be negligible.

• 한국군사과학기술학회지
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• 제22권6호
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• pp.773-783
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• 2019

A numerical analysis of a turbulent flow with a 'large-eddy breakup device(LEBU)' was performed to investigate the influence of the device on the drag of underwater vehicle using commercial CFD code, FLUENT. In the present study, the vehicle drag was decomposed to skin-friction coefficient(C_f) and pressure coefficient(C_p). The variation of the vehicle C_f and C_p were observed with changing location of the device and Reynolds number. As a result, the device decreased the vehicle C_f because it suppressed the turbulent characteristics behind the device. The larger Reynolds number, the higher reduction effect when the device was placed in front part of, and near the vehicle. On the other hand, the device increased/decreased the vehicle C_p with increasing/decreasing turbulent kinetic energy at recirculating flow region behind the vehicle. The total drag change by the device was caused by C_p rather than C_f.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.27-36
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• 2020

Natural convection and thermal stratification phenomena are found in large water pools that are being used as heat sinks for decay heat removal from the reactor core using passive heat removal systems. In this study, the two-phase (water and air) natural convection and thermal stratification phenomena with conjugate heat transfer in the rectangular enclosure were investigated numerically using ANSYS Fluent 17.2 code. The transient numerical simulations of these phenomena in the full-scale computational domain of the experimental facility were performed. Generation of water vapour bubbles around the heater rod and evaporation phenomena were included in this numerical investigation. The results of numerical simulations are in good agreement with experimental measurements. This shows that the natural convection is formed in region above the heater rod and the water is thermally stratified in the region below the heater rod. The heat from higher region and from the heater rod is transferred to the lower region via conduction. The thermal stratification disappears and the water becomes well mixed, only after the water temperature reaches the saturation temperature and boiling starts. The developed modelling approach and obtained results provide guidelines for numerical investigations of thermal-hydraulic processes in the water pools for passive residual heat removal systems or spent nuclear fuel pools considering the concreate walls of the pool and main room above the pool.

• 한국정밀공학회지
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• 제29권9호
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• pp.1003-1011
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• 2012

A new type of gerotor developed in this paper has the inner rotor designed by inserting a polycircular-arc between the hypocycloid and epicycloid curves, and we also suggest that the outer rotor be designed using the closed-form equation for the inner rotor and a method of modification. Thus, it is possible to design a gerotor for which there is no cusp and loop, as in this case undercut is prevented. We developed automated program for rotor design and calculation of the flow rate and flow rate irregularity. And we also demonstrate the superior performance of the gerotor developed in this study by analyzing the internal fluid flow using a commercial computation fluid dynamics-code (CFD).

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 1997년도 International Symposium on Fire Science and Technology
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• pp.305-310
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• 1997

There are many parameters in prediction of forest fire spread. The variables such as fuel moisture, fuel loading, wind velocity, wind direction, relative humidity, slope, and solar aspect have important effects on fire. Particularly, wind and slope factors are considered to be the most important parameters in propagation of forest fire. Generally, slope effect cause different wind distribution in mountain area. However, this effect is disregarded in complex geometry. In this paper, wind is estimated by applying computational fluid dynamics to the forest geometry. Wind velocity data is obtained by using CFD code with Newtonian model and slope is calculated with geometrical data. These data are applied fer 2-dimentional forest fire spreading algorithm with Korean ROS(Rate Of Spread). Finally, the comparison between the simulation and the real forest fire is made. The algorithm spread of forest fire will help fire fighter to get the basic data far fire suppression and the prediction to behavior of forest fire.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.296-296
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• 2015

The aim of this paper is to numerically explore the feasibility of designing a Mini-Hydro turbine. The interest for this kind of horizontal axis turbine relies on its versatility. For instance, in the field of renewable energy, this kind of turbine may be considered for different applications, such as: tidal power, run-of-the-river hydroelectricity, wave energy conversion. It is fundamental to improve the turbine performance and to decrease the equipment costs for achievement of "environmental friendly" solutions and maximization of the "cost-advantage". In the present work, the commercial CFD code ANSYS is used to perform 3D simulations, solving the incompressible Unsteady Reynolds-Averaged Navier-Stokes (U-RANS) equations discretized by means of a finite volume approach. The implicit segregated version of the solver is employed. The pressure-velocity coupling is achieved by means of the SIMPLE algorithm. The convective terms are discretized using a second order accurate upwind scheme, and pressure and viscous terms are discretized by a second-order-accurate centered scheme. A second order implicit time formulation is also used. Turbulence closure is provided by the realizable k - turbulence model. In this study, a mini hydro turbine (3kW) has been considered for utilization of horizontal axis impeller. The turbine performance and flow behavior have been evaluated by means of numerical simulations. Moreover, the performance of the impeller varied in the pressure distribution, torque, rotational speed and power generated by the different number of blades and angles. The model has been validated, comparing numerical results with available experimental data.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.391-398
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• 2008

LES analysis was conducted with in-house CFD code to investigate the turbulence evolution and interaction due to turbulence ring and splash plate in the gas generator. Though chemical reaction was not accounted for, the results can be useful in determining the turbulence characteristics generated by ring and plate. The calculation results show that the installation of turbulence ring can introduce additional turbulences and improve turbulent mixing in the downstream flow. However, the addition of splash plate in the downstream of TR brings totally different shape of perturbation energy and enstrophy distribution for turbulent mixing. This enhancement can be done by the formation of the intensively strong vorticity production and mixing behind the plate. Pressure drop was found to be a reasonable level of about 1% or less of initial pressure in all calculation cases. Also, calculation results revealed that the variation of TR shape and intrusion length did not change the characteristics of turbulent mixing in the chamber. Even though the effect of installation location of splash plate on the turbulent mixing is not investigated yet, calculation results conclude the addition of splash plate leads to the increase in turbulent mixing with an acceptable pressure drop.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.35-41
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• 2012

액체로켓 추력실의 성능 예측 및 초음속 노즐부 형상 설계에 활용 중인 in-house 해석 도구를 이용하여 재생냉각 연소기에 대한 성능/냉각 통합해석을 수행하였으며, 막냉각 유량 및 외곽 분사기열의 혼합비 변화에 따른 연소 성능과 냉각 성능 간 trade-off 경향을 고찰하였다. 향후 막냉각 및 주요 설계인자의 최적화 도구로 활용될 수 있도록 개발 연소기에 대한 시험 결과와의 비교 등을 통하여 수치해석 도구를 검증/개선해나갈 계획이다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.253-258
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• 2012

본 연구에서는 한국의 차세대 중형항공기에 사용될 터보프롭 항공기용 고효율 복합재 프로펠러 블레이드의 설계를 수행하였다. 와류 이론과 블레이드 깃 요소 이론을 활용하여 기본 공력설계 및 성능 해석을 수행하였고 공력설계 결과는 상업용 전산유체해석 프로그램인 ANSYS를 이용한 해석을 통해 확인하였다. 프로펠러 구조 설계 시 카본/에폭시 복합재료가 적용되었으며, 경량화와 구조 안정성 개선을 위하여 스킨-스파-폼 샌드위치 구조 형식를 채택하였다. 제안된 프로펠러 블레이드는 공력 및 구조 해석과 시제품 프로펠러 블레이드의 구조 시험을 통하여 높은 효율과 안전한 구조임이 검토되었다.

• Journal of Ship and Ocean Technology
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• 제7권4호
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• pp.16-31
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• 2003

The finite volume based multi-block RANS code, WAVIS developed at KRISO, is used to simulate the turbulent flows around a submarine with the realizable $\textsc{k}-\varepsilon$ turbulence model. RANS methods are verified and validated at the level of validation uncertainty 1.54% of the stagnation pressure coefficient for the solution of the turbulent flows around SUBOFF submarine model without appendages. Another SUBOFF configuration, axisymmetric body with four identical stem appendages, is also computed and validated with the experimental data of the nominal wake and hydrodynamic coefficients. The hydrodynamic forces and moments for SUBOFF model and a practical submarine are predicted at several drift and pitch angles. The computed results are in extremely good agreement with experimental data. Furthermore, it is noteworthy that all the computations at the present study were carried out in a PC and the CPU time required for 2.8 million grids was about 20 hours to get fully converged solution. The current study shows that CFD can be a very useful and cost effective tool for the prediction of the hydrodynamic performance of a submarine in the basic design stage.