• 대한조선학회논문집
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• 제31권4호
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• pp.41-50
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• 1994

프로펠러 주위의 비압축성 점성유동을 해석하기 위해 멀티그리드 방법을 이용한 Iterative time marching 방법이 적용되었다. 이 방법은 3차원 비압축성 Navier-Stokes 방정식을 움직이는 비직교 일반 좌표계상에서 풀고 있으며, 시간에 대해서는 1차의 정확도 그리고 공간에 대해서는 2차 또는 3차의 정확도를 가지고 있으며 반복계산의 수렴속도를 가속시키기 위해서 멀티그리드방법을 사용하였다. 또한 본 방법은 Vector나 Parallel컴퓨터에 적용이 매우 간편하다는 장점을 가지고 있다. 본 연구 결과와 실험치 혹은 다른 연구자의 계산 결과와 일반적으로 잘 일치하고 있으며, 멀티그리드 방법은 수렴에 필요한 CPU시간을 단축시키고 해의 정확도도 개선함을 보여주었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.223-227
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• 2009

In the present study, a least square weighted residual method and Taylor-Galerkin method were formulated and tested for the discretization of the two hyperbolic type equations of level set method; advection and reinitialization equations. The two approaches were compared by solving a time reversed vortex flow and three-dimensional broken dam flow by employing a four-step splitting finite element method for the solution of the incompressible Navier-Stokes equations. From the numerical experiments, it was shown that the least square method is more accurate and conservative than Taylor-Galerkin method and both methods are approximately first order accurate when both advection and reinitialization phase are involved in the evolution of free surface.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.522-527
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• 2001

Comprehensive numerical computations are made of side-heated squire cavity which is exposed to zero mean g-jitter. Numerical solutions are acquires to the governing two-dimensional Navier-Stokes equations for a Boussinesq fluid. When the system is exposed to pure sinusoidal g-jitter inclined to the vertical axis, in spite of zero mean gravity there exist non zero net flow fields [8]. The resonance phenomenon are observed in moderate Rayleigh number. And, by comprehensive numerical work, unlike[5], it is found that they are related with the overshoot phenomenon of the sudden gravity up problem.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.138-143
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• 2005

In this study, the cross-wind stability of the G7 train and TTX running under the high speed was investigated by using 2-dimensional Reynolds Averaged Navier-Stokes equations. It is very important to analysis the aerodynamic characteristic of bluff body located near a ground at the field of the aeronautical, wind engineering, ground vehicle system. To the point of running stability, it is meaningful to analysis the cross-wind effect to the G7 train and TTX developed by domestic technology. The aerodynamic characteristics of the G7 train equipped by bogie-cover is more superior to the case without bogie-cover. Also 2nd model of TTX has stream-shape body has the more good performance than 1st model of TTX.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.165-169
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• 2009

The effect of the Dirichlet boundary condition for the redistance equation of level set method on the solutionof sloshing problem is investigated by adopting four Dirichlet boundary conditions. For the solution of the incompressible Navier-Stokes equations, P1P1 four-step fractional finite element method is employed and a least-square finite element method is used for the solutions of the two hyperbolic type equations of level set method; advection and redistance equation. ALE (Arbitrary Lagrangian Eulerian) method is used to deal with a moving computational domain. It has been shown that the free surface motion in a sloshing tank is strongly dependent on the type of the Dirichlet boundary condition and the results of broken dam and sloshing problems using various Dirichlet boundary conditions are discussed and compared with the existing experimental results.

• 한국전산유체공학회지
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• 제4권3호
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• pp.1-11
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• 1999

This paper describes the flow field analysis of an automobile with crosswind effects of 15°, 30° 45° and 60° of yaw angles. The governing equations of the 3-D incompressible Navier-Stokes equations are solved by the iterative time marching scheme. The Chimera grid technique has been applied to efficiently simulate the flow around the side-view mirror. The computated surface pressure coefficients have been compared with experimental results and a good agreement has been achieved. The A- and C-pillar vortex and other flow phenomena around the ground vehicle are evidently shown. The variation of aerodynamic coefficients of drag, lift, side force and moments with respect to yaw angle is systematically studied.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.195-199
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• 2005

Wave breaking phenomenon near the fore body of a ship is numerically simulated. The ship advance with uniform velocity in calm water. For the simulation, incompressible Navier-Stokes equations and continuity equation are adopted as governing equations. The simulation is carried out in staggered variable mesh system with finite difference method. Marker and Cell(MAC) method and Marker-Density method are employed to track the free surface. Body boundary conditions are satisfied with the adoption of porosity method and no-slip condition on the hull surface. The ship model has a wedge type fore-body, and the computational domain is an appropriate region around the fore-body. The computation results are compared with some experimental results. Also the difference of the free surface tracking methods are discussed.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.213-217
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• 2005

In this study the water including sediment is assumed that the density is different from fresh water. And the phenomenon inhaled by low pressure around the pipe is numerically simulated in two dimension. The simulation is done using finite difference method in rectangular staggered mesh system and Navier-Stokes equations and continuty equation are employed as governing equations. The method of Irregular leg lengths and stars are adopted to satisfy boundary condition of body boundary. Marker-Density method is used to calculate the density of mixed flow. Also SGS turbulence model is applied to consider vortex smaller then grid at high Renolds number. This study is to analyze inhalation phenomenon of mixed flow with sediment and to verify the numerical method for mixed flow. To verify the numerical results are compared with experimental results

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.99-109
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• 1998

This paper describes the analysis of flow and aeroacoustic field around a car-like body. The governing equations, 3-D unsteady incompressible Navier-Stokes equations, are solved with the iterative time marching scheme. The Chimera grid technique has been applied to efficiently simulate the flow around the side-view mirror, After the flow field analysis has been converged, the aerodynamic noise analysis of the side-view mirror has been performed by solving Ffowcs Williams and Hawkings equation. From the present numerical simulation, the A- and C-pillar vortex are evidently shown and the aerodynamic noise level induced by the side-view mirror is predicted to about 100dB.

• 대한기계학회논문집B
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• 제36권3호
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• pp.315-324
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• 2012

본 연구는 가연성 기체로서 에틸렌-공기 혼합물로 채워져 있는 관에서 장애물과 굽은 관에 의한 지형적 효과에 따라 변화하는 충격파와 화염의 상호 작용, 화염 가속, 연소폭발천이 현상을 수치적으로 살펴보았다. 여기서 사용되는 모델은 지배방정식으로 Navier-Stokes 방정식과 경계조건 처리 방법으로 ghost fluid 기법을 사용하였으며 지형적 영향을 달리한 여러 모델링을 통하여 화염과 강한 충격파의 충돌에 의한 열점 생성과 화염 전파의 지연 혹은 가속 현상을 확인하였다. 추가적으로 평균 화학적 에너지 발생률이 대략 20 MJ/($g{\bullet}s$)에서 폭굉으로 천이한다는 사실을 확인하였다. 그리고 동일 위치 열점 생성에도 불구하고 폭굉의 발생 시기가 반응물의 부재와 화염면 전방의 온도와 압력 차에 의해 지연될 수 있음을 확인하였다.