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RISS 인기검색어
- 검색키워드
- 저자 : Dinesh Myilsamy (검색결과 4 건)
- 무료
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Large eddy simulation of the backdraft dynamics in compartments with different opening geometries
Dinesh Myilsamy,오창보,최병일 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5
Large eddy simulation (LES) was performed to investigate backdraft in reduced-scale compartments using the fire dynamics simulator. Mixing-controlled fast chemistry combustion model was adopted in the LES predictions of the backdraft phenomenon. The effect of the opening geometry of the compartment on the critical fuel percentage required for backdraft occurrence was numerically investigated by considering compartments with a door or a slot opening. The LES with the mixing-controlled fast chemistry combustion model provided reasonable results for the gravity current and backdraft development process in the reduced-scale compartments. The predicted results of the critical fuel percentage for backdraft occurrence were in good agreement with those obtained by previous experiments on door and slot opening geometries. The LES also predicted the trend in peak pressure with increasing fuel concentration inside the compartment reasonably well. The oxygen concentration of the entrained airflow inside the compartment affected the peak pressure during backdraft development. The peak pressures for the compartment with a slot opening were higher than those for a compartment with a door opening at the same fuel concentration. The difference in the peak pressures between the two compartment geometries was attributed to the difference in the entrained oxygen concentration caused by different ignition times.
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Numerical investigation of prediction performance of design fire curves for a tunnel fire
Dinesh Myilsamy,Chang Bo Oh,이치영 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.9
The prediction performance of design fire curves is numerically investigated for tunnel fire using the fire dynamics simulator (FDS). A large eddy simulation (LES) was adopted in the simulation of a previous 750 kW tunnel fire experiment. Based on the experimental heat release rate, t 2 -fire growth, quadratic and exponential design fire curves (DFCs) are mathematically constructed and adopted in the FDS simulation. The predictions of each DFCs are compared against the experimentally measured smoke temperature, smoke travel time, and carbon monoxide (CO) concentration. In addition, the prediction performance of the mixture fraction (MF) and mixing controlled fast chemistry (MCFC) combustion models, is compared. The simulation results of the MF and MCFC models are similar except for the CO concentration features. For the performance of the DFCs, t 2 -fire growth curve with the MF combustion model is the most effective combination, which demonstrated the most reasonable agreement with the experimental data.
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사각채널 내 수소-공기 혼합기의 DDT에 대한 RANS 기반 수치해석 연구
Dinesh Myilsamy,오창보 한국화재소방학회 2023 한국화재소방학회논문지 Vol.37 No.1
In this study, a numerical code based on Reynolds-Averaged Navier-Stokes (RANS) method was developed usingOpenFOAM to investigate the deflagration to detonation transition (DDT) phenomenon in hydrogen-air mixture gas insidea rectangular channel. The channel was modeled with a thickness of 80 mm and a length of 2000 mm. The numericalsimulations were compared with the experimental results and it was found that the developed code qualitatively wellsimulated the transition process from deflagration to detonation. It was also found that the pressure distribution and reactionprogress variables can be useful indicators to understand the instant and location of DDT occurrence. The location of DDTwas found to be at the point where the shock wave and the position of the flame front matched. Furthermore, it wasobserved that the higher the height of the obstacle, the earlier the DDT occurred, but the magnitude of pressure after theDDT did not correlate with the height of the obstacle. 본 연구에서는 폭연에서 폭굉으로 천이되는 현상(deflagration to detonation transition, DDT)의 전산해석에 적합한reynolds-averaged navier-stokes (RANS) 기반의 OpenFOAM 수치코드를 개발하였다. 개발된 코드를 이용하여 두께 80 mm,길이 2000 mm인 사각 채널 내부의 수소-공기 예혼합기에서 발생하는 DDT 현상을 수치적으로 고찰하였다. 개발된코드는 채널 내부의 수소-공기 예혼합기의 점화에서 발생하는 폭연과 폭굉으로의 천이과정을 정성적으로 잘 모사하는 것을 확인하였다. 또한 압력분포와 반응진행변수는 DDT의 발생시점과 위치를 잘 파악하는 데 유용한 변수가 될수 있음을 확인하였다. DDT 특성과 관련해서는 채널 내부의 장애물 높이가 높은 경우가 DDT 발생시점이 빠르게나타났으며 DDT가 발생한 위치에서는 충격파와 화염면 위치가 정확하게 일치하는 것을 잘 알 수 있었다. 추가적으로 장애물 높이가 높은 경우가 DDT 발생시점은 빠르지만 DDT 발생 이후의 압력 최고값도 높게 나타나지는 않는것으로 확인되었으며 이것은 충격파와 반사파의 상호작용 등 복잡한 현상에 기인하는 것으로 파악되었다.
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