• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1996년도 춘계 학술대회논문집
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• pp.33-39
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• 1996

An incompressible flow stover based on the unstructured finite volume method has been developed. The flow domain is discretized by triangles in 2D or tetrahedra in 3D. The convective and viscous fluxes are obtained using edge connectivities of the unstructured meshes. The pressure-velocity coupling is handled by the artificial compressibility algorithm due to its computational efficiency associated with the hyperbolic nature of the resulting equations. Laminar test flow problems are computed and presented with a comparison against other numerical solutions or experimental results.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2004년도 분과위원회 연구과업 보고서
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• pp.223-245
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• 2004

최근, 자유수면을 갖는 비압축성 유체의 해석을 위해 Hirt and Nichols(1981)가 제안한 VOF법이 자유수면을 취급하는 많은 학문분야에서 활발히 활용되고 있다. 특히, 일본에서 잠제에 의한 쇄파해석에 암전 등(1994)이 처음으로 VOF법을 적용한 이래 많은 연구자에 의한 공동연구의 결과로 개발된 CADMAS-SURF(해안개발기술연구 Center, 2001)는 사용자가 직접 입·출력을 제어할 수 있는 효과적인 2차원파동장의 해석프로그램으로 알려져 있다. 국내에서는 김 등(2001, 2002)이 최초로 VOF-SOLA법을 이용한 수치파동수로를 제안하고 잠제주변의 파동장해석을 수행하고 있다. (중략)

• 기계저널
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• 제33권1호
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• pp.22-32
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• 1993

본드선도는 물리적 등가가 적용되는 모든 상사 시스템을 대단히 조직이며 일관성 있게 모델링할 수있을 뿐만 아니라 시스템의 동적 방정식을 제어동역학 관점에 유리한 상태방정식으로 직접 유도할 수 있다. 또한 본드선도는 모델링 단계에서 무시된 각 요소들의 동적 특성 즉, 기계시스 템에서 회전축의 탄성처짐이나 운동 물체들 사이의 마찰 효과 전기 . 자기시스템에서 자속유출량, 그리고 유체 . 유압시스템에서 밀봉부분의 유량손실이나 압축성 유체 특성 등을 기곤에 구성된 본드선도의 변경 없이 각 특성들이 나타나는 본드상에 적절한 접합요소와 함께 단순히 첨가하여 고려할 수 있기 때문에 모델링 과정을 다시 반복하지 않고도 무시된 동적 특성들이 전체시스템에 미치는 영향을 파악할 수 있다. 특히 본드선도가 에너지 변환 장치나 에너지 유동 메카니즘이 복잡한 다에너지역 시스템 등에 거동이 전체시스템에 미치는 효과를 시각적으로 보다 세밀히 파악할 수 있을 뿐만 아니라 구성된 본드선도에 인과관계를 할당하여 본드선도의 접합요소를 통하여 유도된 최종적인 동적 방정식이 현실적으로 실현 가능한 물리시스템인지 파악할 수 있어 본드선도 모델링 단계에서 시스템을 묘사하는 동적 방정식의 옳고 그름을 평가할 수 있다. 이와 같이 본드선도는 기계, 전기 . 자기, 유체 . 유압, 열 시스템 및 이들이 조합된 복잡한 다에너지역 시스템 등을 효과적으로 모데링할 수 있는 매우 유용한 동적 시스템 모델링 방법이다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.452-455
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• 2008

A new passive control technique of cavity-induced pressure oscillations has been investigated numerically for a supersonic two-dimensional flow over open rectangular cavities at Mach number 1.83 just upstream of a cavity, in which a sub-cavity system is installed on the backward-facing step of the main cavity. A third-order TVD (Total Variation Diminishing) finite difference scheme with MUSCL is used to discretize the spatial derivatives in the unsteady compressible Navier-Stokes equations. The results obtained show that the present sub-cavity system is very effective in reducing cavity-induced pressure oscillations. The results also showed that the resultant amount of attenuation of cavity-induced pressure oscillations was dependent on the length and thickness of the flat plate, and also on the depth of the sub-cavity used as an oscillation suppressor.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.64-67
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• 2007

In the present study, the wind pressure transients on platform screen door in side platforms caused by passing trains have been investigated numerically. The transient compressible 3-D full Navier-Stokes solution is obtained with actual operational condition of subway train and the moving mesh technique is adopted considering the train movement. To achieve more accurate analysis, the entrance and exit tunnel of platform are included in a computational domain and detailed shape of train is also modeled Numerical analyses were conducted on five operational condition which are different velocity variation of subway train, existence of stationary train and passing each other trains. The results show that pressure load on platform screen door is maximized when the two trains are passing each other. It is also seen from the computational results that the maximum pressure variation was found to be satisfactory to various foreign standards.

• 한국전산유체공학회지
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• 제12권4호
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• pp.1-6
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• 2007

In the present study, the wind pressure transients on platform screen door in side platforms caused by passing trains have been investigated numerically. The transient compressible 3-D full Navier-Stokes solution is used with actual operational condition of subway train by adopting the moving mesh technique considering the train movement. To achieve more accurate analysis, the entrance and exit tunnel connecting the stations are included in a computational domain with modeling the detailed shape of the train. Numerical analyses are conducted on five operational conditions which include the variation of the train speed, case with or without the train stopped in the other track, and case for two trains passing each other inside the station. The results show that pressure load on platform screen door is maximized when the two trains are passing each other. It is also seen from the computational results that the maximum pressure variation for the cases considered in the present study is found to be satisfactory to various foreign standards.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.168.1-168.1
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• 2010

본 연구에서는 기존 지중열교환기용 뒤채움재인 벤토나이트 그라우트의 대안으로 시멘트 그라우트의 물리적 역학적 특성을 평가하였다. 실내 시험을 통하여 시멘트 그라우트의 배합비 및 첨가재에 따라 열전도도와 유동성, 일축압축강도에 미치는 영향을 평가하였다. 또한, 실제 지중열교환기용 파이프 내 순환유체의 온도변화가 시멘트 그라우트의 재료적 안정성에 미치는 영향을 검토하기 위해 $-5^{\circ}C$와 $50^{\circ}C$를 한 주기로 하여 일축압축강도를 반복적으로 측정하였다. 냉난방 운전에 따른 시멘트 그라우트와 순환 파이프 접촉면의 양호한 부착성 유지 여부를 판단하기 위해 시멘트 그라우트에 HDPE 파이프를 삽입한 시료의 등가 투수계수를 Flexible wall permeameter를 이용하여 장기간 측정하였다. 순환유체의 온도변화 모사에 따른 일축압축강도는 주기가 반복될수록 강도가 감소하는 경향이 나타났다. HDPE파이프를 삽입한 시료의 등가 투수계수는 순환수의 온도에 따라 증감하다가 $1.02{\times}10^{-9}cm/sec$로 수렴하였다.

• 한국전산유체공학회지
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• 제4권1호
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• pp.53-61
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• 1999

Two-dimensional, unsteady, incompressible and compressible Navier-Stokes codes are developed for the computation of the viscous turbulent flow over high-lift airfoils. The compressible code involves a conventional upwind-differenced scheme for the convective terms and LU-SGS scheme for temporal integration. The incompressible code with pseudo-compressibility method also adopts the same schemes as the compressible code. Three two-equation turbulence models are evaluated by computing the flow over single and multi-element airfoils. The compressible and incompressible codes are validated by predicting the flow around the RAE 2822 transonic airfoil and the NACA 4412 airfoil, respectively. In addition, both the incompressible and compressible code are used to compute the flow over the NLR 7301 airfoil with flap to study the compressible effect near the high-loaded leading edge. The grid systems are efficiently generated using Chimera overlapping grid scheme. Overall, the κ-ω SST model shows closer agreement with experiment results, especially in the prediction of adverse pressure gradient region on the suction surfaces of high-lift airfoils.

• 한국해양공학회지
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• 제16권5호
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• pp.15-20
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• 2002

In this research, the finite difference lattice Boltzmann method(FDLBM) is used to analyze gravity currents in the lock exchange configuration that occur in many natural and man-made situations. At a lock those are seen when a gate is suddenly opened, and, in the atmosphere, when the thunderstorm outflows make a cold front. At estuaries in the ocean, the phenomenon is found between fresh water from a river and salt water in the sea. Since such interesting phenomena were recognized, pioneers have challenged to make them clear by conducing both experiments and analysis. Most of them were about the currents of liquid or Boussinesq fluids, which are assumed as incompressible. Otherwise, the difference in density of two fluids is small. The finite difference lattice Boltzmann method has been a powerful tool to simulate the flow of compressible fluids. Also, numerical predictions using FDLBM to clarify the gravity currents of compressible fluids exhibit all features, but typically observed in experimental flows near the gravity current head, including the lobe-and-cleft structure at the leading edge.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 추계 학술대회논문집
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• pp.90-95
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• 1998

The two-dimensional incompressible and compressible Navier-Stokes codes are developed for the computation of the viscous turbulent flow over high-lift airfoils. Incompressible code using pseudo-compressibility and dual-time stepping method involves a conventional upwind differencing scheme for the convective terms and LU-SGS scheme for time integration. Compressible code also adopts an FDS scheme and LU-SGS scheme. Several two-equation turbulence models (the standard $k-{\varepsilon}$ model, the $k-{\omega}$ model. and $k-{\omega}$ SST model) are evaluated by computing the flow over single and multi-element airfoils. The compressible and incompressible codes are validated by computing the flow around the transonic RAE2822 airfoil and the NACA4412 airfoil, respectively. Both the results show a good agreement with experimental surface pressure coefficients and velocity profiles in the boundary layers. Also, the GA(W)-1 single airfoil and the NLR7301 airfoil with a flap are computed using the two-equation turbulence models. The grid systems around two- and three-element airfoil are efficiently generated using Chimera grid scheme, one of the overlapping grid generation methods.