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2차원 해면효과익의 비정상 성능에 대한 수치적 시뮬레이션
박일룡(I. R. Park),전호환(H. H. Chun) 한국해양공학회 1995 韓國海洋工學會誌 Vol.9 No.2
A numerical model capable of simulating 2-D airfoil flying over in the vicinity of the waves is discussed. Instead of treating the problem as a heaving oscillation one above the rigid flat wall, sources distributed on the prescribed wave profile. The wave deformation due to the airfoil is assumed to be negligible and treated as a rigid undulated wall. The source and vortex are distributed on the surface of the foil. It is found that the variation of CL with wave steepness is severe and that the lift variation due to waves deceases as the wing height above the water surface increases.
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.
박일룡(I.R. Park),임근태(G.T. Yim),김제인(J.I. Kim),박철수(C.S. Park) 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.1
Numerical investigations of bubble column flows were performed to validate the predictive capabilities of the commercial CFD solver STAR-CCM+. An Eulerian-Eulerian approach was used for the simulation of the two-phase flow in a bubble column. The numerical method takes into account interactive forces between both phases: drag force, lift force, turbulent dispersion force and wall lubrication force near the wall surface. The constituent moments of bubble size distribution function are transported with individual phase velocities with breakup and coalescence models to account for size dependent bubble motion. In the numerical results, the dependances of turbulence and lift models on the solutions were investigated. Validation of the present simulation results against available experimental and numerical data was carried out with respect to bubble plume oscillation, liquid velocity and gas hold-up. Finally, a reasonable agreement between the simulation and experimental results was obtained.
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.
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.
RANS법을 이용한 선박 프로펠러 날개 끝 보오텍스 유동 해석
박일룡(I.R. Park) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.2
It has been highly demanded to improve the accuracy of CFD(Computational Fluid Dynamics) methods for the assessment of the hydrodynamic performance of marine propellers in cavitating and non-cavitating flows. This paper presents a validation study on the numerical simulation of the tip vortex flow of a non-cavitating marine propeller SVA VP1304. The calculations are carried out by using the Reynolds averaged Navier-Stokes(RANS) approach, where the Reynolds Stress Model(RSM) is used for turbulence closure. The present paper contains a grid dependence test for the propeller open water simulations and a special emphasis is placed on conducting a local grid adaptation on the blade tip and in the tip vortex to reasonably reproduce the velocity and the pressure in the tip vortex flow field. The numerical results are compared with the experimental validation data, which are published in the second International Symposium on Marine Propulsors 2011(SMP’11). The present numerical results show a reasonable agreement with the experiments.
천수에서 전진하는 선박의 선체 및 추진기 주위 유동 수치 해석
박일룡(I.R. Park) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.4
This paper provides numerical results of the simulation for the flow around the hull and the propeller of KCS model ship advancing in shallow water conditions. A finite volume method is used to solve the unsteady Reynolds averaged Navier-Stokes(RANS) equations, where the wave-making problem is solved by using a volume-of-fluid(VOF) method. The wave formed near the hull surface in shallow water conditions shows a deep trough dominant pattern that causes the loss of buoyancy followed by hull squat. The flow past the hull increases as the depth of water decreases. However, the axial flow velocity around the stern shows a reduction in magnitude by the effect of shallow water accompanied by the hull-propeller interaction. As a results, the thrust and torque coefficient increase about 8.3% and 6.2%, respectively for a depth of h/T = 3.0 corresponding to a depth Froude number of F<SUB>h</SUB>=0.693. The resistance coefficient increases about 11.6% at this Froude number condition.
박일룡(I.R. Park),박대진(D.J. Park),김제인(J.I. Kim),서성부(S.B. Suh),백부근(B.G. Paik),안종우(J.W. Ahn),김기섭(K.S. Kim) 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.3
The cavitation inception of a two-dimensional hydrofoil is studied numerically by using the unsteady Reynolds averaged Navier-Stokes method that includes a cavitation model explaining the phase change between the water and vapour. The cavitation inceptions of the NACA0022 hydrofoil at various angles of attack are estimated after following the dependence tests of grid and turbulence model on the wetted flow around the NACA0012 section. In this paper, cavitation inception is determined when the computed cavitation volume approaches to zero value by gradually increasing cavitation number. In the numerical results, the computed sheet cavitations attached to the suction side of the hydrofoil show a close agreement with the cavitation observations in the KRISO medium-sized cavitation tunnel. Finally, the cavitation inception bucket predicted by the current cavitation simulation shows a better agreement with the experimental data than the two results of the potential flow and the minimum pressure analyses.