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.

한국산과 중국산 '사과배' 과실의 생태적 특성

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)

가상 경계 방법을 이용한 유동 해석 기법에 관한 기초 연구

박일룡,하만영,양승호 대한기계학회 2004 大韓機械學會論文集B Vol.28 No.6

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.

KRISO 대형 캐비테이션터널 시험조건의 함정 모형선 반류에 대한 수치해석적 연구

박일룡(Il-Ryong Park),김제인(Je-In Kim),김기섭(Ki-Sup Kim),안종우(Jong-Woo Ahn),박영하(Young-Ha Park),김명수(Myoung-Soo Kim) 대한조선학회 2016 大韓造船學會 論文集 Vol.53 No.6

SUBOFF 잠수함 모델의 캐비테이션터널 조건 저항 및 자항 수치해석 연구

박일룡(I.R. Park),김제인(J.I. Kim),서성부(S.B. Suh),설한신(H.S. Seol) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.3

In this paper, numerical investigation of the resistance and self-propulsion of the SUBOFF submarine model in the KRISO large cavitation tunnel was carried out by using the Reynolds averaged Navier-Stokes method and Reynolds stress model for turbulence closure. This study followed the sensitivity analysis of grid and turbulence models done by Byeon et al.[11] which was for the numerical estimation of the resistance of the SUBOFF model in DTRC towing tank. In the numerical results, the resistances and the nominal wake field were validated by the experimental data of the cavitation tunnel. After blockage corrections, the computed resistances showed a good accordance with those of the DTRC towing tank test free from blockage effects. Self-propulsion simulations for wetted and cavitating flow conditions were performed on the basis of thrust identity approach and resulted in a good agreement with the measured self-propulsion data and cavitation observations for the propeller.

표면장력 효과를 고려한 이상유동 해석법 개선에 관한 연구

박일룡(Il-Ryong Park) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.5

The present paper proposes a coupled volume-of-fluid (VOF) and level-set (LS) method for simulating incompressible two-phase flows that include surface tension effects. The interface of two fluids and its motion are represented by a VOF method designed using high resolution differencing schemes. This hybrid method couples the VOF method with an LS distancing algorithm in an explicit way to improve the calculation of the normal and curvature of the interface. It is developed based on a rather simple algorithm to be efficient for various practical applications. The accuracy and convergence properties of the method are verified in an simulation of a single gas bubble rising in a three-dimensional flow with a large density ratio.

불규칙 파랑 중 카페리선의 SRtP 소요마력 수치 추정 연구

박일룡(Il-Ryong Park),김제인(Je-in Kim),서성부(Sung-Bu Suh),김진(Jin Kim),김광수(Kwang-Soo Kim),김유철(Yoo-Chul Kim) 한국해양공학회 2019 韓國海洋工學會誌 Vol.33 No.1

This paper considers a numerical assessment of the self-propulsion performance of a damaged ferry carrying cars in irregular waves. Computational fluid dynamics(CFD) simulations were performed to see whether the ferry complied with the Safe Return to Port (SRtP) regulations of Lloyd’s register, which require that damaged passenger ships should be able to return to port with a speed of 6 knots (3.09 m/s) in Beaufort 8 sea conditions. Two situations were considered for the damaged conditions, i.e., 1) the portside propeller was blocked but the engine room was not flooded and 2) the portside propeller was blocked and one engine room was flooded. The self-propulsion results for the car ferry in intact condition and in the damaged conditions were assessed as follows. First, we validated that the portside propeller was blocked in calm water based on the available experimental results provided by KRISO. The active thrust of starboard propeller with the portside propeller blocked was calculated in Beaufort 8 sea conditions, and the results were compared with he experimental results provided by MARIN, and there was reasonable agreement. The thrust provided by the propeller and the brake horsepower (BHP) with one engine room flooded were compared with the values when the engine room was not flooded. The numerical results were compared with the maximum thrust of the propeller and the maximum brake horse power of the engine to determine whether the damaged car ferry could attain a speed of 6 knots(3.09 m/s).

수상 함정 기포 마스크 벨트에서 생성된 기포 유동에 관한 수치해석 연구

박일룡(I.R. Park),김제인(J.I. Kim),박철수(C.S. Park),김건도(G.D. Kim),임근태(G.T. Yim) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.3

This paper provides the results of the basic numerical study on the bubble generation mechanism of an air bubble mask belt device to reduce engine noise by creating bubble curtain around the hull of a surface ship. To analyze two-phase flows, a large eddy simulation (LES) approach coupled with a volume of fluid (VOF) method was adopted. This numerical approach was verified by comparison with the experimental and other numerical results for a single bubble rising problem in a stationary flow field. Due to laminar and turbulent break-up phenomena, the bubble mask belt produced bubbles of various sizes ranging from 100μm to 3000μm depending on the flow conditions. The present numerical results will be used to determine the air flow rate of the mask belt and other flow conditions required to generate a desired size bubble at a given ship speed.

NACA 66₂-415 단면을 가지는 타원형 수중익의 날개 끝 보오텍스 및 캐비테이션 수치해석

박일룡(Il-Ryong Park),김제인(Je-in Kim),설한신(Han-Sin Seol),김기섭(Ki-Sup Kim),안종우(Jong-Woo Ahn) 한국해양공학회 2018 韓國海洋工學會誌 Vol.32 No.4

This paper provides quantification of the effects of the turbulence model and grid refinement on the analysis of tip vortex flows by using the RANS(Reynolds averaged Navier-Stokes) method. Numerical simulations of the tip vortex flows of the NACA 662-415 elliptic hydrofoil were conducted, and two turbulence models for RANS closure were tested, i.e., the Realizable k-ε model and the Reynolds stress transport model. Numerical results were compared with available experimental data, and it was shown that the data for the Reynolds stress transport model that were computed on the finest grid system had better agreement in reproducing the development and propagation of the tip vortex. The Realizable k-ε model overestimated the turbulence level in the vortex core and showed a diffusive behavior of the tip vortex. The tip vortex cavitation on the hydrofoil and its trajectory also showed good agreement between the current numerical results that were obtained using the Reynolds stress transport model and the results observed in the experiment.