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거친 사각채널에서 열전달과 유체유동 특성에 관한 실험 및 수치해석
강호근,배성택,이대희,안수환,Kang, Ho-Keun,Baer, Sung-Taek,Lee, Dae-Hee,Ahn, Soo-Whan 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.2
Experiment and three dimensional numerical investigations of incompressible turbulent flow through square channels with one- and two-sided ribbed walls are performed to determine pressure drop and heat transfer. The CFX(version 5.7) software package is used for the computation. The ribbed walls have a $45^{\circ}$ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The numerical results coincide with experimental data that obtained for $7,600{\le}Re{\le}24.900$, the pitch-to-rib height ratio (p/e) of 8.0. and the rib height-to-channel hydraulic diameter ratio ($e/D_h$) of 0.0667. The results show that values of local heat transfer coefficient and friction factor in the channel with two-sided ribbed wall are higher than those in the channel with one-sided ribbed walls.
BEMT를 적용한 20kW 수평축 풍력터빈 형상설계 및 성능해석
강호근,남청도,이영호,김범석,Kang, Ho-Keun,Nam, Cheong-Do,Lee, Young-Ho,Kim, Beom-Seok 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.6
The optimum design and the performance analysis software called POSEIDON for the HAWT (Horizontal Axis Wind Turbine) is developed by use of BEMT, which is the standard computational technique for prediction of power curves of wind turbines. The Prandtl's tip loss theory is adopted to consider the blade tip loss. The lift and the drag coefficient of S-809 airfoil are predicted via X-FOIL and the post stall characteristics of S-809 also are estimated by the Viterna's equations.$^{[13]}$ All the predicted aerodynamic characteristics are fairly well agreed with the wind tunnel test results. performed by Sommers in Delft university of technology. The rated power of the testing rotor is 20kW(FIL-20) at design conditions. The experimental aerodynamic parameters and the X-FOIL data are used for the power Prediction of the FIL-20 respectively The comparison results shows good agreement in power prediction.
강호근,안수환,김정환,Kang Ho-Keun,Ahn Soo-Whan,Kim Jeong-Whan 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.5
Two-dimensional turbulent flows past a square cylinder and cavity noise are simulated by the finite difference lattice Boltzmann method with subgrid turbulence model. The method, based on the standard Smagorinsky subgrid model and a single-time relaxation lattice Boltzmann method, incorporates the advantages of FDLBM for handling arbitrary boundaries. The results are compared with those by the experiments carried out by Noda & Nakayama and Lyn et al. Numerical results agree with the experimental ones. Besides, 2D computation of the cavity noise generated by flow over a cavity at a Mach number of 0.1 and a Reynolds number based on cavity depth of 5000 is calculated. The computation result is well presented a understanding of the physical phenomenon of tonal noise occurred primarily by well-jet shear layer and vortex shedding and an aeroacoustic feedback loop.
강호근,Kang, Ho-Keun The Korean Society of Marine Environment and safet 2013 해양환경안전학회지 Vol.19 No.2
일반적으로 액체가스운반선은 인화성 화물이나 독성물질을 운반한다. 이러한 화물들은 폭발, 화재 및 인명손상을 가져올 수 있기 때문에, 액체가스운반선의 거주구역, 서비스 구역 및 통제실은 가스의 유입이 원천적으로 차단되도록 설계한다. 이러한 이유로, IMO IGC 코드의 멤브레인형 LNG선박의 화물탱크에 설치되는 벤트 출구의 높이는 노출갑판상 B/3 또는 6m 중 큰 것 이상으로 하고 작업구역 및 전후부 통행로, 갑판상의 저장탱크 및 화물설계 액위보다 6m 이상 높게 설치하여야 한다라고 규정하고 있다. 또한 LNG 시장이 점진적으로 증가하면서, LNG선박의 크기도 증가해 왔다. 때문에 현 규정에 의하면 LNG선박의 벤트의 높이는 선박 폭(B)에 비례하기 때문에 상당히 높아져야 할 것이며, 이는 높은 벤트 마스트(Mast)로 인하여 작업의 어려움 및 전방 시야를 방해하는 등 항해의 어려움을 초래한다. 본 연구에서는 멤브레인형 LNG선의 Sea-trial시에 측정하였던 데이터 및 CFD유동해석을 통해 LNG선박 화물탱크의 벤트 출구의 높이에 대한 적합성 평가를 수행한다. Liquefied gas carriers generally transport cargoes of flammable or toxic nature. Since these cargoes may cause an explosion, fire or human casualty, the accommodation spaces, service spaces and control stations of liquefied gas carriers should be so located as to avoid ingress of gas. For this reason, the paragraph 8.2.9 of IGC Code in IMO requires that the height of vent exits should be not less than B/3 or 6 m whichever is greater, above the weather deck and 6 m above the working area and the fore and aft gangway to prevent any concentration of cargo vapor or gas at such spaces. Besides as known, the LNG market has been growing continually, which has led to LNG carriers becoming larger in size. Under this trend, the height of a vent will have to be raised considerably since the height of a vent pipe is generally decided by a breadth of a corresponding vessel. Accordingly, we have initiated an examination to find an alternative method which can be used to determine the safe height of vent masts, instead of the current rule requirement. This paper describes the dispersion characteristics of boil-off gas spouted from a vent mast under cargo tank cool-down conditions in the membrane type LNG carriers.
내부자유도를 갖는 차분래티스볼츠만 모델에 의한 에지톤의 수치계산
강호근,김은라,오세경,Kang Ho-Keun,Kim Eun-Ra,Oh Se-Kyung 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.8
A lattice BGK model based on a finite difference scheme with an internal degree of freedom is employed and it is shown that a diatomic 9as such as air is successfully simulated In a weak compressive wane problem and Coutte flow, the validity and characteristics of the applied model are examined. With the model. furthermore. we present a 2-dimensional edge tones to predict the frequency characteristics of discrete oscillations of a jet-edge feedback cycle by the FDLB model (I.D.F FDLBM) in which any specific heat ratio $\gamma$ can be chosen freely. The jet is chosen long enough in order to guaranteed the Parabolic velocity profile of a jet at the outlet. and the edges have of an angle of $\alpha$=$23^{0}$ and $20^{0}$. A sinuous instability wane with real frequency resulting from Periodic oscillation of the jet around the edge is propagated on the upper and lower of wedge.
강호근(Ho-Keun Kang),김유택(Yu-Taek Kim),이영호(Young-Ho Lee) 한국유체기계학회 2003 유체기계 연구개발 발표회 논문집 Vol.- No.-
Two-dimensional direct numerical simulation of the edge-tones by the finite difference lattice Boltzmann method (FDLBM) is presented. We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing the conventional FDLBM, and also use a boundary fitted coordinates. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. It is clarified that the sound wave generated in rather wide region and individual vortices do not affect the sound wave propagation.
Vortex-Edge의 상호작용에 기인한 유동소음의 전산해석
강호근(HO-KEUN KANG),김은라(EUN-RA KIM) 한국해양공학회 2004 韓國海洋工學會誌 Vol.18 No.5
An edge tone is the discrete tone or narrow-band sound produced by an oscillating free shear layer, impinging on a rigid surface. In this paper, we present a 2-D edge tone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle, using the finite difference lattice Boltzmann method (FDLBM). We use a modified version of the lattice BGK compressible fluid model, adding an additional term and allowing for longer time increments, compared to a conventional FDLBM, and also use a boundary fitted coordinates system. The jet is chosen long enough in order to guarantee the parabolic velocity profile of the jet at the outlet, and the edge consists of a wedge with an angle of α=23. At a stand-off distance, the edge is inserted along the centerline of the jet, and a sinuous instability wave, with real frequency, is assumed to be created in the vicinity of the nozzle and propagates towards the downstream. We have succeeded in capturing very small pressure fluctuations, resulting from periodical oscillations of a jet around the edge. The pressure fluctuations propagate with the speed of sound. Its interaction with the wedge produces an non-rotational feedback field, which, near the nozzle exit, is a periodic transverse flow, producing the singularities at the nozzle lips.
Simulation of Compressible Stratified Flow by the Finite Difference Lattice Boltzmann Method
강호근(Ho-Keun Kang),쯔타하라 미시히사(Michihisa Tsutahara),김정환(Jeong-Hwan Kim),이영호(Young-Ho LEE) 한국전산유체공학회 2001 한국전산유체공학회 학술대회논문집 Vol.2001 No.-
중력이 작용하는 압축성유체를 고려함에 있어, 밀도성층 뿐만아니라 엔트로피 성층의 고려도 중요하다. 본 연구에서 압축성격자볼츠만 유체모델을 이용한 차분계산법을 이용하여 2 차원 채널에서 성층류의 전형식인 형상인 선택취수현상을 시뮬레이션 하였으며, 본 모델의 유효성을 확인하였다. 또한 비점성, 비압축성유체의 선택취수흐름과의 차이에 관해서 압축성의 관점에서 고찰하였다.
차분격자볼츠만법에 ALE모델을 적용한 이동물체 주위의 흐름 및 유동소음의 수치모사
강호근(HO-KEUN KANG) 한국해양공학회 2006 韓國海洋工學會誌 Vol.20 No.1
In this paper, flowfield and acoustic-field around moving bodies are simulated by the Arbitrary Lagrangian Eulerian (ALE) formulation in the finite difference lattice Boltzmann method. Some effects are checked by comparing flow about a square cylinder in ALE formulation and that in the fixed coordinates, and both agree very well. Matching procedure between the moving grid and fixed grid is also considered. The applied method in which the both grids are connected through buffer region is shown to be superior to moving overlapped grid. Dipole-like emissions of sound wave from harmonically vibrating bodies in two- and three-dimensional cases are simulated.