• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.3
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• pp.345-352
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• 1985

본 연구에서는 내류(internal flow)에서 유로가 비대칭으로 급확대될 경우의 박리현상과 유동현상을 고찰하였다. 비대칭 급확대 채널에서의 층류영역에서 난류영 역까지의 유동현상을 B.F. Armaly, C.E. Thomas는 실험적 해석과 유한요소법을 사용하 여 이론적 해석을 하였고 Donald. M. Kuehn, Denham & Patrick, Kwon, Patrick J. Ro- ache, Anand Kumar등은 같은 모델에 대해서 실험적 해석과 유한차분법을 사용하여 이 론적 해석을 하였으며 지금까지의 유한해석법에 의한 연구는 입구와 출구조건이 같은 경우 및 밀폐 공간 혹은 한면의 속도가 주어지는 밀폐공간등에 대해 수행되어 왔으나 본 연구에서는 입구와 출구조건이 같지 않은 2차원, 비대칭 급확대 채널에서의 유동현 상을 유한해석법으로 해석하여 실험치와 비교하였다.

• The Journal of Engineering Geology
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• v.19 no.2
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• pp.205-215
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• 2009

The conventional numerical models to analyze flow in subsurface porous media under the transient state usually generate numerical oscillation and unstability due to local flux domain for critical cases such as infiltration into initially dry soil during rainfall period. In this case, it is required refined mesh and small time step, but it decrease efficiency of computation. In this study, numerical unstability in discontinuity domain is removed by applying particle tracking algorithm to simulate unsteady subsurface flow with inflow boundary condition. Finally the hybrid LE FEM improving numerical stability is proposed. The hypothetical domains with unsteady uniform and nonuniform flow field were used to demonstrated algorithm verification. In comparison with analytic solution, we obtained reasonable results and conducted simulation of hypothetical 3-D recharge/pumping area. The proposed algorithm can simulate saturated/unsaturated porous media with more practical problems and will greatly contribute to accuracy and stability of numerical computation.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.57-63
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• 2018

IR thermography is a non-invasive method and used for the visualization of the surface temperature of the model. However, this technique only derives 2D results and not quantitative data. The goal of this study is to apply the 3D mapping technique for IR thermography. The wind tunnel model is an ogive-cylinder with a wind speed of 20 m/s ~ 80 m/s and the angle of attack ranging from $0^{\circ}$ to $90^{\circ}$. The real location of the model was made to correspond with the position of the IR image using the makers. Based on this result, quantitative results were obtained. The 3D mapping method was verified by comparing the separation point and the theoretical value.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.116-122
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• 1988

Interfacial shear stresses have been determined for countercurrent stratified flow of air and water in a nearly-horizontal rectangular channel, based upon measurements of pressure drop, gas velocity profiles and mean film thickness. A dimensionless correlation for the interfacial friction factor has been developed as a function of the gas and liquid Reynolds numbers. Equivalent surface roughnesses for the interfacial friction factor have been calculated using the Nikuradse correlation and have been compared with the intensity of the wave height fluctuation on the interface. The results show that the interfacial shear stress is mainly affected by turbulent mixing near the interface due to the wave motion rather than by the roughened surface.

• Journal of the KSME
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• v.32 no.2
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• pp.201-209
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• 1992

유동의 가시화를 위한 CG와 애니메이션에 대하여 설명하였다. CG처리를 위해서는 대형 컴퓨터 보다도 워크 스테이션(WS), 특히 3차원 그래픽스 기능을 갖춘 GWS가 훨씬 편리하다. GWS와 CG용 소프트 웨어는 최근 몇 년 사이에 눈에 띄게 발전하여 일본의 경우만 하더라도 20여 사 에서 100여 종에 가까운 GWS가 판매되고 있다. 그러나 이것들에 사용되고 있는 CPU는 R3000, R6000, MC68040, MC88100, PA-RISC, SPARC, POWER-아키텍춰 등으로 비교적 그 수가 적고, 사용된 CPU에 따라 대개의 성능이 결정된다. 유동의 가시화를 위한 소프트웨어도 상당한 수가 판매되고 있고, 또 대부분 범용성이 있어 쉽게 사용할 수 있는 것들이 많다. 이와 같은 추세로 금후 CG에 의한 유동의 가시화가 자연적으로 확대 이용되어 갈 것이고, 가시화기술 발전 또한 가속될 것으로 보인다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.3
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• pp.197-201
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• 2009

As one of the promising model on the multiphase fluid mixtures, the Lattice-Boltzmann Method(LBM) is being developed to simulate flows containing two immisible components which are different mass values. The equilibrium function in the LBM can have a nonideal gas model for the equation of state and use the interfacial energy for the phase separation effect. An example on the phase separation has been carried out through the time evolution. The LBM based on the statistic mechanics is appropriate to solve very complicated flow problems and this model gives comparative merits rather than the continuum mechanics model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2681-2690
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• 2010

This paper proposes 3D facial modeling system without using 3D scanner and camera or expensive software. This system enables efficient 3D facial modeling to cost reduction and effort saving for natural facial modeling. It detects edges of component of face using edge detection based on fuzzy logic from any 2D image of front face. It was mapped fitting position with 3D standard face model by detected edge more correctly. Also this system generates 3D face model more easily through floating and flexible control and texture mapping after fitting that connection of control point on detected edge from 2D image and mesh of 3D standard face model.

• The KSFM Journal of Fluid Machinery
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• v.14 no.3
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• pp.10-17
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• 2011

Free energy based lattice Boltzmann method (LBM) has been used to simulate the contact angle and the bubble necking with large density ratio. LBM with the proper contact angle model is able to reduce the spurious currents and eliminate the singularity in the contact lines. The numerical results of the contact angles are satisfied with the Youngs law. For bubble necking flows, simulations are executed for various viscosities and contact angles. The phenomena of the bubble necking are simulated successfully and the subsequent results are presented. The present method is also applicable to the nucleate boiling flows.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.200-214
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• 1993

This paper presents the results of fluidelastic instability analysis performed for the U-tube bundle of a Westinghouse model 51 steam generator, one of the recirculating types designed at an early stage, in which the principal region of external cross-flow is associated with the U-bend portion of tube. The prerequisites for this analysis are detailed informations of the secondary side flow conditions in the steam generator and the free vibration behaviours of the U-tubes. In this study, the three-dimensional two-phase flow field in the steam generator has been calculated employing the ATHOS3 steam generator two-phase flow code and the ANSYS engineering analysis code has been used to calculate the free vibration responses of specific U tubes under consideration. The assessment of the potential instability for the suspect U-tubes, which is the final analysis process of the present work, has been accomplished by combining the secondary side velocity and density distributions obtained from the ATHOS3 prediction with the relative modal displacement and natural frequency data calculated using the ANSYS code. The damping of tubes in two-phase flow has been deduced from the existing experimental data by taking into account the secondary side void fraction effect. In operation of the steam generator, the tube support conditions at the tube-to-tube support plate intersections due to either tube denting degradation or deposition of tube support plate corrosion products or ingression of dregs. Thus, various hypothetical cases regarding the tube support conditions at the tube-to-tube support plate intersections have been considered to investigate the clamped support effects on the forced vibration response of the tube. Also, the effect of anti-vibration bars support in the curved portion of tube has been examined.

• Journal of Korea Water Resources Association
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• v.36 no.1
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• pp.129-142
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• 2003

In this study, the conduct of underground water flow system with 3 dimensions is interpreted in order to examine closely the actual condition regarding the flow of the underground water which is forecast from the tunnel segment and the interpretation result which selects the design and the construction technique of the tunnel segment was applied. Also, an obstacle to construct that relates with the underground water flow in construction duration in advance will be able to apply with information that is necessary in order to establish the countermeasure. The objective tunnel is the BEOPGI tunnel segment that is 2 parallel tunnels that are a one-way 2 lane and the parameters of the MODFLOW model executing the boring investigation and the permeability examination were presumed. The underground water flow of the excavation tunnel inside was interpreted by the MODFLOW model using the parameters which is presumed and two values which compared with calculated value and observed value are the same almost. Also, when the underground water discharge quantify that followed in tunnel excavation tries to compare, the underground water total discharge quantity from tunnel point of start until destination was presumed as 0.0269㎥/day/$m^2$.