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사고 선박 손상부 형상이 기름 유출량에 미치는 영향 연구
박일룡 해양환경안전학회 2022 해양환경안전학회지 Vol.28 No.4
This paper shows the numerical prediction of the change in oil outflow rate according to the orifice shape of a damaged ship by using the computational fluid dynamics (CFD) analysis method. It also provides discharge coefficients for various orifice shapes to be used in theoretical prediction approaches. The oil outflow from the model ship was analyzed using a multiphase flow method under the condition that the Froude and Reynolds number similitudes were satisfied. The present numerical results were verified by comparing them with the available experimental data. Along with the aspect ratio of the orifice and the wall thickness of the cargo tank, the effects of the orifice shapes defined by mathematical figures on the oil outflow were investigated. To consider more realistic situations, the investigation of the effect of the crushed iron plate around the damaged part was also included. The numerical results confirmed the change in oil outflow time for various shapes of the damaged part of the oil tank, and discharge coefficients that quantify the viscous effects of those orifice shapes were extracted. To verify the predicted discharge coefficients, they were applied to an oil spill estimation equation. As a result, a good agreement between the CFD and theoretical results was obtained. 본 논문은 CFD 해석법을 이용하여 사고 선박의 손상부 형상에 따른 기름 유출량 변화를 예측하고, 이론 추정식에서 이를 고려할 수 있는 방출계수 도출 결과를 소개한다. Froude수와 Reynolds수 상사를 만족하는 조건에서 다상유동 해석법을 사용하여 모형선 크기의 기름 유출 문제를 다루었다. 수치해석 결과는 알려진 실험 결과와 비교하여 검증하였다. 수학적 형상들로 정의한 손상부 형상의 변화와 함께 손상부 가로세로비와 기름탱크 두께의 변화가 기름 유출 유동에 미치는 영향을 조사하였다. 보다 현실적인 상황을 고려하기 위해 손상부의 찧어진 철판의 영향에 대한 해석도 포함하였다. 수치해석 결과를 통해 사고 선박의 손상부 형상에 따른 기름 유출량의 변화를 확인하였으며, 다양한 손상부 형상이 가지는 점성 영향을 방출계수로 정량화하여 추출하였다. 본 논문에서 제시하는 방출계수에 대한 검증을 위하여 알려진 기름 유출량 주정식에게 적용하였으며, CFD 해석과 좋은 일치를 얻었다.
박일룡,황용수,이재창 충남대학교 농업과학연구소 2002 농업과학연구 Vol.29 No.1
Postharvest characteristics of 'Pingguoli' fruit produced between China and Korea were compared to find an ecological difference. There was a difference in fresh weight per fruit, thus, fruit weight produced in Korea was much higher than those in China. However, no significant differences were confirmed in the level of soluble solid content and flesh firmness. The acidity of Korean 'Pingguoli' was higher than Chinese ones. The external appearance of Korean 'Pingguoli' was not attractive due to the rough and rugged surface. Thus, the prospect of 'Pingguoli' cultivation in Korea seems not to b e promised. The general trend of respiration and ethylene evolution during storage did not significantly differed but the amount of CO_2 and ethylene production was higher in fruits produced in China. There was a strong similarity in respiration and ethylene evolution pattern to typical climacteric fruits. Thus, 'Pingguoli' is considered as a climacteric fruit. Even though the rate of ethylene production of 'Pingguoli' was relatively high, the storability of 'Pingguoli' showed a strong potential. The further studies in postharvest physiology of pear using 'Pingguoli' and in its breeding potentials as a source of long storage life are needed.^2)
경사진 평행평판 내 고 점성유체의 혼합대류 열전달 특성 및 가시화에 관한 연구
박일룡,배대석 대한설비공학회 2006 설비공학 논문집 Vol.18 No.9
Experiment and numerical calculation have been performed to investigate mixed convection heat transfer between inclined parallel plates. Particle image velocimetry(PIV) with thermo-sensitive liquid crystal(TLC) tracers is used for visualizing and analysis. This method allows simultaneous measurement of velocity and temperature fields at a given instant of time. Quantitative data of the temperature and velocity are obtained by applying the color- image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. The governing equations are discretized using the finite volume method.The results are presented for the Reynolds number ranges from 0.004 to 0.062, the angle of inclination,, from 0 to 45 degree and Prandtl number of the high viscosity fluid is 909. The results show velocity, temperature and mean Nusselt numbers distributions. It is found that the periodic flow of mixed convection between inclined parallel plates is shown at 0°≤<30°, Re<0.062, and the flow pattern can be classified into three patterns which depend on Reynolds number and the angle of inclination. The minimum Nusselt numbers occur at Re=0.05 regardless of the angle of inclination.
다상유동 RANS법을 이용한 수상 함정 주위 기포 층 두께 예측
박일룡(I.R. Park) 한국전산유체공학회 2022 한국전산유체공학회지 Vol.27 No.1
This paper shows the numerical analysis of bubbly flows generated by an air bubble masking belt installed in the midships of a surface ship. Numerical simulations were performed using the Reynolds Averaged Navier-Stokes(RANS) Eulerian multiphase(EMP) flow method and the bubble layer thickness around the model and full scale ship, bubble diameter distribution, and changes in hull resistance were investigated. The layer of bubbles became thicker downstream of the both hulls as the air flow rate increased. Since the large bubbles moving downstream of the hulls rose to the free surface due to the buoyancy, the average diameter of the bubbles inside the bubble layers tended to decrease as it went downstream. Although the thickness of bubble layers according to the air flow rates at the model and full scale conditions showed a tendency to roughly follow the scale ratio, a further study on the accurate correlation should be conducted in the future. Both the model and full scale ship showed an increase in pressure resistance after air injection, and a decrease in friction resistance. The distribution of air bubbles in the propeller planes followed the nominal wake characteristics, showing more bubbles at the full scale conditions.