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균일 전단류내에 있는 원봉주위의 국소 대류 물질 전달에 관한 실험적 연구
류명석,성형진,정명균 대한기계학회 1989 대한기계학회논문집 Vol.13 No.4
본 연구에서는 평균속도구배를 용이하게 변화시킬 수 있는 전단유동 발생기를 제작하였다. 최고속도구배는 38se $c^{-1}$까지 얻을 수 있으며 최대중심선 속도는 15m/sec까지이다. 10개의 채널(두께 2mm인 알루미늄판)로 유동단면을 등분하 였으며, 각 채널의 내부저항조절 방법으로 마름모형태의 막대인 knob을 설치하였다. A naphthalene sublimation technique based on the heat/mass transfer analogy is used to investigate the circumferential mass transfer from a circular cylinder in an approaching uniform shear flow. Experiments are performed in a wind tunnel (450*450m $m^{2}$ with a shear flow generator which is specially manufactured for generating variable shear rates(S). The effects of an approaching shear flow are correlated with mass transfer coefficients. It is found that the local mass transfer rate on a circular cylinder is characterized with the shear parameter $K^{d}$ defined as Sd/ $U^{c}$ , where d is the radius of cylinder and $U^{c}$ is the approaching velocity at the center of cylinder. The angle on the corresponding to minimum Sherwood number is approximately proportional to the shear parameter on an upper and down number is approximately proportional to the shear parameter on an upper and down circular cylinder (0< $K^{d}$ <0.132). Changes on the averaged mass transfer rate are not significant for small $K^{d}$ , which are slightly proportional to K$d^{2}$ but the local mass transfer rates are significantly changed with the approaching shear flow.
비대칭 급확대 관로 유동장 내의 열전달 해석에 수정된 경계층 방정식의 적용 가능성 추정
류명석,맹주성,Lyu, Myoung-Seok,Maeng, Joo-Sung 대한설비공학회 1985 설비저널 Vol.14 No.4
This paper describes an economical prediction procedure for heat transfer phenomenon through a channel containing an abrupt asymmetric expansion in flow cross-seetional area. Numerical solutions for the flow field are obtained by the finite difference numerical method applied to the modified boundary layer equations. Modified boundary energy equation is used to analyze heat transfer as modified boundary momentum equation. Predictions of the method compare very favorable with exprimental data. Results of this study by modified boundary layer equation are as follows : 1. The computation time required for the scheme is at least an order of magnitude less than for the numerical solution of the full Navier-stokes and Energy eguations. 2. In laminar flow, the maximum heat transfer occurs downstream of the reattachment point.
차량 연비 향상을 위한 대형 디젤엔진 차량의 엔진 냉각 및 부대장치 연구
류명석,Lyu, Myung-Seok 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.3
Recently it is strongly required to develop the better fuel economy as well as basic power performance based on strict emission legislation. This paper focuses on studies of the engine cooling and ancillaries system among fuel economy factors in the developing stage. Firstly through the analysis of the current specifications, it is assessed whether each components may be designed properly, not overdesigned. Secondly, it is predicted how the fuel economy of each components can be improved. Finally the results are confirmed by vehicle field test equppted with the updatedcomponents. This study found good agreementbetween the prediction and the field test on the vehicle fuel economy improvements of the heavy duty engine vehicle with updated components such as engine cooling and ancilliaries.
류명석,강성모,김용모,Ryu, Myeong-Seok,Gang, Seong-Mo,Kim, Yong-Mo 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.3
The transient incompressible flow behind the axisymmetric bluff body is numerically simulated using the random vortex method(RVM). Based on the vorticity formulation of the unsteady Navier-Stokes equations, the Lagrangian approach with a stochastic simulation of diffusion using random walk technique is employed to account for the transport processes of the vortex elements. The numerical solutions for 2-dimensional recirculating flow behind a backward-facing step in the laminar range of Reynolds number are compared with experimental data. The present simulation focuses on the transitional flow regime where the recirculation zone behind the bluff body becomes highly unsteady and large-scale vortex eddies are shed from the bluff body wake due to intrinsic shear layer instabilities. The unsteady vertical flow structures and the mixing characteristics behind the bluff body are discussed in detail.
류명석(M.S.Lyu),구영곤(Y.G.Ku),김경훈(K.H.Kim),김경희(K.H.Kim),길재성(J.S.Ghil) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.11_2
The importance of intake system can not be overstressed in the recent heavy duty commercial vehicle design. The basic requirements of intake system are to have less flow resistance and better air cleaning performance which have direct effects on the performance and service life of engine. In order to improve the performance of engine intake system, the flow phenomena in the intake system should be fullly understood. With readilly availble CFD code. the numerical analysis becomes the more reliable tools for flow optimization in recent design work.<br/> In this research. flow field in the intake system was analyzed by Star-CD, the 3-D computaional fluid dynamic code. Especially, the flow inside of air cleaner was thoroughly analyzed. Pressure distribution and velocity profile in the air cleaner and intake duct was obtained. Having the dust seperated from incoming air at the expence of less pressure- drop is the ultimate goal for the research.<br/>
류명석(Myungseok Lyu),신재영(Jaeyong Shin),진봉용(Bongyong Jin) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This study was initiated to evaluate the cooling performance of CAC (charged air cooler) and radiator in the engine room of a mini bus. So we had firstly to predict the mass flow rate coming from radiator grille and front bumper opening using computational fluid dynamics (CFD) simulation based on 3D configuration. And simulations were carried out for different cooling module layout and bumper opening hole size on same vehicle operating condition. Simulation results show that CAC cooling performance at reverse protecting plate-applying model was much efficient than that of the bumper opening hole size-increasing model in IMTD point of view. Part of the CFD simulation results was compared to with experimental data It was confirmed that the CFD approach using STAR-CD based on pursuing no-compromise solution could provide design engineers with useful design information in the early design stage of vehicle development<br/>
차 개구형상이 엔지룸내 유동에 미치는 영향에 관한 수치연구
류명석(M.S.Lyu),이은준(E.J.Lee),구영곤(Y.G.Ku) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.6_1
The knowledge of air flow in an engine room has become more and more important in recent car design. The fluid flow in the engine compartment was investigated by numerical analysis. Due to the complex geometry of the engine compartment, mesh generation is a time-consuming job. In this research, the "ICEM" code was used to generate meshes by the Cartesian mesh model. The Reynolds-averaged Navier Stokes equations, together with the porous flow model for radiator and condenser, were solved. Computation was perfomed for the steady, incompressible, and high speed viscous flow, adopting the standard K-E turbulence model. The "STAR-CD" code was used as a solver. The effect of car front openning area on the flow in engine room was also investigated.<br/>