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서용권,Suh, Y.K. 대한설비공학회 1994 설비공학 논문집 Vol.6 No.1
A numerical study has been performed on enhancement of heat transfer in a forced convection of the modified driven-cavity flow which was previously found by the author to give a regular or chaotic stirring depending on the parameter value. It is found that for the present case wherein heat is transmitted between fluid and the surrounding walls, the chaotic stirring enhances the heat transfer at high Peclet numbers. The optimal condition of the flow modulation for the best heat transfer can be predicted by purely investigating the hydrodynamic facet, i.e. the stirring effect.
서용권,Suh, Y.K. 대한설비공학회 1992 설비공학 논문집 Vol.4 No.4
A two-dimensional Benard-convection system with a phase-change material inside has been analysed. The main purpose of the present study is to clarify the basic reason of the hysteresis found by the previous investigators. The interface between the solid and the liquid is assumed to be planar. The analysis was performed with heat transfer rates under the steady state on the interface. It was found that the hysteresis occurs due to the abrupt increase in the heat transfer rate at the onset of natural convection in the classical Benard-convection system. The spectral method was applied to obtain the steady solution of the natural convection for the specific material and to confirm the hysteresis phenomenon.
마이크로 채널 내 사다리꼴 전극의 제타 포텐셜 변화에 따른 혼합효과 증대에 대한 수치해석적 연구
서용권(Y.K. Suh),허형석(H.S. Heo),康金芬(J.F. Kang) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.3
This paper presents the numerical results of fluid flow and mixing in a micro fluidic device for electro-osmotic flow (EOF) with an trapezoidal electrode array on the bottom wall (ETZEA). Differently from previous EOF in a channel which only transports fluid in colloidal system, E1ZEA can also be utilized to mix a target liquid with a reagent. In this study we propose a method of controlling fluid flow and mixing enhancement. To obtain the flow and mixing characteristics, numerical computations are performed by using a commercial code, CFX-10, and a self-made code LBM-D. It was found that the flow near the trapezoidal electrode in the ETZEA is of 3-D complex flows due to the zeta potential difference between the trapezoidal electrode and channel walls, and as a consequence the hetrogeneous zeta potential on the electrodes plays an important role in mixing the liquid.
서용권(Y. K. Suh) 한국전산유체공학회 2004 한국전산유체공학회지 Vol.9 No.4
In this study a stretching-mapping method is proposed for calculating the materials I stretching exponents, which are to be used in quantification of the mixing effect. In this method, the mapping tensor associated with the deformation of each fluid material is first obtained. Then deformations of a lot of materials are obtained by applying the mapping tensor. The local stretching rates and their space-average values are next computed with the mapped deformations. Application to a simple time-periodic flow within a cavity shows that the method is indeed effective compared with the conventional method; i.e. the mapping method is fast and yields the same results as the conventional one.
서용권(Y.K. Suh) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.3
In this study we present the numerical methods that can be used in visualization of the flow and mixing patterns in a cavity driven by a top lid. The basic flow field within the cavity has been obtained by using a simple numerical scheme. The invariant manifold also called unstable manifold was then attained to represent the mixing pattern within the cavity. It was shown that care must be taken in calculating the trajectories of the fluid particles especially near corners of the cavity. The numerical results show excellent agreement with those obtained experimentally by other research group.
내연기관 실린더 헤드 조립체 내부의 냉각수 유동 및 열전달에 관한 연구
서용권(Y.K. Suh),허성규(S.G. Heo),김병휘(B.H. Kim) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.1
In this study we investigated the characteristics of fluid flow and heat transfer within a coolant passage in the cylinder head assembly of an internal combustion engine by using a commercial CFD code, CFX The complex coolant passage of the cylinder head assembly was modelled by suitable choice of a grid system and careful attention was paid in the construction of meshes near the walls where significant cooling occurs. To treat the simultaneous heating and cooling of the combustion walls we invented a methodology allowing a heat source within the solid wall and the convective cooling at the interface between the solid and the fluid. We managed to reproduce the experimental results by adjusting parameters appropriately. We have found that high temperature was concentrated at the surface of the cylinder jacket. It turned out that the effect of oil cooling from the piston head was unexpectedly significant. On the other hand the effect of cooling from the ambient air is almost negligible. The CFD method proposed in this study is believed to be useful in the early stage of the design of the engine-cooling system.
엇갈림형 스크류 채널 내부의 스톡스 유동과 혼합특성 해석
서용권(Y. K. Suh) 한국전산유체공학회 2004 한국전산유체공학회지 Vol.9 No.4
The three-dimensional Stokes flow within a staggered screw channel is obtained by using a finite volume method. The geometry is intended to mimic the single screw extruder having staggered arrangement of flights. The flow solution is then subjected to the analysis of the studing performance. In the analysis of the stirring performance, the stretching-mapping method developed by the author is employed for calculating the materials' stretching exponents, which are to be used in Quantification of the mixing effect. The numerical results indicate that the staggered geometry gives indeed far much better stirring-performance than the standard (nonstaggered) flight geometry. It was also shown that care must be given to the selection of the basis planes for evaluating the local stretching rate, and it turns out that the best method (H -method) has its basis plane just on the half way between the past and future evolution of fluid particles subjected to the deformation. In evaluating the stretching exponent, the expansion ratio must be considered which is one of the characteristic differences of the actual three-dimensional flows from the two-dimensionmal counterparts. The larger axial pressure-difference causes in general the smaller stirring performance while the flow rate is increased. The smaller channel length also increases the stirring performance.
Induced Steady Flow around Two Oscillating Circular Cylinders
Y.K. Suh(徐龍權),S.W. Oh(吳世旭),K.M. Han(韓健模) 한국해양공학회 1987 韓國海洋工學會誌 Vol.1 No.1
두 개의 동일한 원통이 두 중심점을 잇는 선에 對하여 수직인 方向으로 振動할 때 發生되는 定常流에 對한 解를 구하였다. 관련된 諸變數들간의 어떤 假定下에서 本 問題는 Stokes問題가 될 수 있었다. 流動함수를 級數展開하였으며, 級數의 係數函數는 penta-diagonal matrix를 풀어 求할 수 있었다. 解의 結果에 의하면 원통 주위에 몇개의 소용돌이가 생겼으며 그 소용돌이의 數는 두 원통間의 거리에 따라 달라졌다. 두 원통間의 거리가 커짐에 따른 漸近的 性質을 單一 원통의 경우와 比較하여 確認하였다.
서용권(Y.K. Suh),강상모(S.M. Kang),허형석(H.S. Heo) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.2
In the present, The theoretical and numerical results of gas flow characteristics inside a swirl injector are presented. For this purpose a one-dimensional (theoretical) model and 2D/3D CFD models are proposed for use in the design of the injector. It was found that contradictory to the classical theory about the compressible flow, the swirl has a significant effect on the mass flow rate and the choking conditions. It was found that the one-dimensional model provides reasonably accurate results compared with the 2D/3D numerical results, and thus can be used at the initial stage of the swirl-injector design process.