http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
2-D Rarefied Gas Flow in Transition Regime Past a Flat Slider
崔瑞源 弘益大學校 科學技術硏究所 1993 科學技術硏究論文集 Vol.3 No.-
평판 슬라이더를 통과하는 천이영역의 희박기체 유동을 직접 전산모사 방법으로 해석하였다. 균일한 유체는 질소이며 2원자 분자인 질소분자들의 충돌과정은 현상적 모델인 energy-sink 모델로 취급됐다. 벽에 반사된 분자들은 벽과 완벽한 온도 평형을 이룬다고 가정되었다.
최서원,강호철,홍종태,이상길 한국군사과학기술학회 1999 한국군사과학기술학회지 Vol.2 No.2
Supersonic flows over an EFP(explosively formed projectile) have been calculated by a high-order conservation law scheme and two-layer $$textsc{k}$-{\varepsilon}$ model on hybrid viscous unstructured mesh. To verify the accuracy and robustness of the developed code, two basic flows about airfoils are computed and results are compared with existing experimental data and computational results. The comparisons confirm the validity of the code and justify our use for such a highly supersonic and viscous flow over a blunt body. Complex flow features of supersonic flows over an EFP are clearly captured and show agreements with the flow visualization. From the interaction of oblique shocks near the surface of flare, flow structures, that were not identified by previous experimental results, are discovered as a result of present computation.
최서원,백영호,김두연,강호철,Choe, Seo-Won,Baek, Yeong-Ho,Kim, Du-Yeon,Gang, Ho-Cheol 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.1
Heat-transfer enhancement is seeked through modifications of fin surface. Real life plate-fin heat exchangers have complex three-dimensional geometries. Fins can have arrays of dimples and are attached to rows of penetrating tubes. To isolate the effect of surface modification, we model the real flow by a two-dimensional channel flow with a dimple on one side. The flow is analysed by solving the incompressible Navier-Stokes equation by a finite volume method on a generalized boundary-fitted coordinate. Results show a trapped vortex inside the dimple for all cases computed. Local maximum of Nusselt number occurs near the downstream end of the dimple, due to such a vortex. Location of the vortex does not change with respect to the wall temperature change, but moved downstream when Reynolds number increases. This, together with the results that in all cases vortex core is somewhat downstream of the dimple center, suggests that the mean flow above continuously feeds the kinetic energy to the recirculating flow. Heat transfer enhancement and pressure losses are studied through analysing the relevant dimensionless parameters like, Nusselt number and friction factor. In all cases computed, dimpled channel flow experiences less pressure loss than two-dimensional Poiseuille flow.
압축성 전단층 불안정성의 critical layer 해석
崔瑞源 弘益大學校 科學技術硏究所 1994 科學技術硏究論文集 Vol.4 No.-
Instability of compressible free shear layer is studied by analysing spatial evolution of a pair of oblique waves whose amplitude growth is dictated by critical layer nonlinearity. The resulting amplitude equation has a downstream singularity in all cases for inviscid compressible shear layers, and the amplitude grows exponentially as the waves approach the singularity. The analysis is more relevant to experimental findings than the incompressible one1) because the oblique modes grow faster than the two-dimensional modes in linear regime10).
최서원,Choe, Seo-Won 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.4
Results of flat plate compressible boundary layer calculation, based on discrete formulation of DSMC method, are presented in low Mach number and low Knudsen number range. The free stream is a uniform flow of pure nitrogen at various Mach numbers in low pressures (i.e. rarefied gas). Complete thermal accommodation and diffuse molecular reflections are used as the wall boundary condition, replacing unreal no-slip condition used in continuum calculations. In the discrete formulation of DSMC method, there is no need to use ad hoc assumptions on transport properties like viscosity and thermal conductivity, instead viscosity is calculated from values of other field variables (velocity and shear stress). Also the results are compared with existing self-similar continuum solutions. In all Mach number cases computed, velocity slip is most pronounced in regions near the leading edge where continuum formulation renders the solution singular. As the boundary layer develops further downstream, velocity slips asymptote to values that are between 10 to 20% of the magnitude of free stream velocity. When the free stream number density is reduced, so the gas more rarefied, the velocity slip increases as expected.
지진 관측자료를 기반으로 한 한반도 지진 발생 확률 예측
최서원,장원철,Choi, Seowon,Jang, Woncheol 한국통계학회 2017 응용통계연구 Vol.30 No.5
2016년 9월 경주 지진 이후 원자력발전소, 고층 빌딩, 주택, 교량 등 우리 사회의 설비 자산들이 과연 지진으로부터 얼마나 안전한가, 앞으로 안정성을 담보하기 위해 어떤 정책을 펼쳐야 하는가에 대한 관심이 높아졌다. 본 논문에서는 한반도에서 발생한 역사지진 및 계기지진 목록을 데이터로 사용하여, 멱법칙 분포를 통해 한반도 지진 기록의 크기 분포를 설명하는 모수를 추정한다. 또한 추정한 모수를 바탕으로 미래에 한반도에서 일정 규모 이상의 지진이 발생할 확률을 계산한다. 한반도 미래 지진 발생 확률 계산 모형을 통해 지진 위험도를 파악하고자 하는 것이 본 논문의 목적이다. Earthquake concerns have grown after a remarkable earthquake incident on September 12th, 2016 in Gyeongju, Korea. Earthquake forecasting is gaining in importance in order to guarantee infrastructure safety and develop protection policies. In this paper, we adopt a power-law distribution model to fit past earthquake occurrences in Korea with various historical and modern seismological records. We estimated power-law distribution parameters using empirical distributions and calculated the future probabilities for large earthquake events based on our model. We provide the probability that a future event has a larger magnitude than given levels, and the probability that a future event over certain levels will occur in a given period of time. This model contributes to the assessment of latent seismological risk in Korea by estimating future earthquake probabilities.
崔瑞源 弘益大學校 科學技術硏究所 1996 科學技術硏究論文集 Vol.7 No.1
Exterior ballistics of a typical high-speed projectile is studied through a flow-visualization experiment and a compressible Navier-Stokes computation. Experiment produced a schlieren photograph that adequately shows the characteristic features of this complex flow, namely two kinds of oblique cone shocks and turbulent wake developing into the downstream. A hybrid scheme of finite volume-element method is used to simulate the compressible Navier-Stokes solution on an unstructured mesh. Osher's approximate Riemann solver is used for the convection term and Galerkin method is used for the viscous term. Fourth-order Runge-Kutta method is used for time-stepping. A two-layer k-ε turbulence model is used to simulate the turbulent wakes accurately. Axi-symmetric flow and two-dimensional flow with an angle of attack have been computed. 2-D calculation shows that effect of angle of attack is not severe. Axi-symmetric results of the computation agrees well with the flow visualization.