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시간과 격자 크기 변화에 따른 원주후류해석의 경제적 수치기법
맹주성,김용대,최일곤,Maeng, Joo-Sung,Kim, Yong-Dae,Choi, IL-Kon 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.5
The purpose of this study is to present the most effective numerical scheme to calculate the unsteady flows. In order to calculate the flow quantities of flow past a circular cylinder, Three-time level and five convective schemes are applied to unsteady and convective terms, respectively. The values obtained are compared with those from the existing experimental and numerical studies. At Reynolds numbers up to 160, time intervals can be expanded 10 times of Implicit Euler scheme using Three-time level method, and it is found that QUICK and CUI schemes work much stable than others even if less grid density conditions. The combination of Three-time level and QUICK scheme gives high resolutions for laminar unsteady problems with PC level.
다익 팬/스크롤 시스템의 로터 내부 유동 특성에 관한 실험적 연구
맹주성,윤준용,안태범,윤종은,한덕전,Maeng, Joo-Sung,Yoon, Joon-Yong,Ahn, Tae-Beom,Yoon, Jong-Eun,Hahn, Doug-Jeon 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.5
Detailed characteristics of the mean flow field inside the rotor of a multiblade fan with scroll are presented in this paper by measurements and visualizations. The measurements were taken with a five-hole probe and conformed by smoke test. How field is distinguished clearly in 3 regions with respect to the flow directions. The first region is near the exit of scroll where the fluid flows the opposite direction to the rotation of rotor. The second is opposite side of the scroll exit where the fluid flows the same direction to the rotation of rotor. The third is the region where the fluid flows toward the blades directly with the largest values comparatively. The strongest recirculation is happened in the second region, and the weakest one is in the third region. This complex configuration makes the flow field highly non-uniform and may cause to generate a noise and ineffective flow efficiency.
비압축성 Navier-Stokes 방정식에 대한 Krylov 부공간법의 적용
맹주성,최일곤,임연우,Maeng, Joo-Sung,Choi, IL-Kon,Lim, Youn-Woo 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.7
The preconditioned Krylov subspace methods were applied to the incompressible Navier-Stoke's equations for convergence acceleration. Three of the Krylov subspace methods combined with the five of the preconditioners were tested to solve the lid-driven cavity flow problem. The MILU preconditioned CG method showed very fast and stable convergency. The combination of GMRES/MILU-CG solver for momentum and pressure correction equations was found less dependency on the number of the grid points among them. A guide line for stopping inner iterations for each equation is offered.
다익 홴/스크롤 시스템의 형상변수와 내부 유동장 특성과의 관계
맹주성,유달현,이광호,박인규,Maeng, Joo-Sung,Yoo, Dal-Hyun,Lee, Kwang-Ho,Park, ln-Gyu 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.9
This paper describes that the size of inactive zone can be directly applied to design multiblade fan/scroll system. From the experimental studies using a five hole pitot tube and smoke test, it is found that the size of inactive zone has linear relations with the mean velocity of impeller inlet and cut-off angle gives a great influences to the fan efficiency. For the practical design, a function related with geometric parameters(i.e. inner radius, cord length, cut-off clearance and cut-off angle) of fan/scroll system is suggested. By using these formulas, the size and distribution of inactive zone can be predicted without the measurements through the full domain, it can be possible to use them to know the efficiency improvement for new model designed.
맹주성(Joo-Sung Maeng),윤준용(Joon-Yong Yoon),권종환(Jong-Hwan Kwon) 한국전산유체공학회 1996 한국전산유체공학회 학술대회논문집 Vol.1996 No.-
A general three-dimensional numerical model, based on the solution of the Navier-Stokes equations, is developed to describe the flow in a wide range of three-dimensional geometries. Here, the equations of fluid motion are fully transformed into the computational coordinates, and the pressure-velocity coupling is made through the SIMPLER algorithm. The momentum equations are discretized using analytic solutions of the linearized equations. It is validated against the experiment of Humphrey who measured the laminar flow field in a 90°square curved duct. The results suggest that this numerical model may be extended to more complex flows, and to turbulent flows.
맹주성(Joo-Sung Maeng),한석영(Seog-Young Han),김종필(Jong-Pill Kim) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.9
In general, shape optimization design of the flow system has done to obtain the effects, which are required in the engineering fields. Most of these designs are accomplished by empirical or numerical analysis. But, in empirical analysis case, it is difficult to obtain an optimal shape in the feasible design region. And, in numerical method case, it usually needs many design parameters, because of the required object-function. In this paper, we present a newly numerical analysis, the growth-strain method having only one design parameter. That optimizes a shape by distributing a design parameter such as dissipation energy to be uniformed in the flow system. Also, we apply this shape design process to the three-flow systems, and then we identify that the resulting shape approaches the known optimal shape in the numerical values. Consequently, we confirm that the proposed method is very efficient and practical in the shape optimization of the flow system.
비압축성 Navier-Stokes 방정식의 수렴 가속을 위한 예조건화 Krylov 부공간법과 다중 격자법의 결합
맹주성(Joo Sung Maeng),최일곤(IL Kon Choi),임연우(Youn Woo Lim) 한국전산유체공학회 1999 한국전산유체공학회 학술대회논문집 Vol.1999 No.-
In this article, combination of the FAS-FMG multi-grid method and the Krylov subspace method was presented in solving two dimensional driven-cavity flows. Three algorithms of the Krylov subspace method, CG, CGSTAB(Bi-CG Stabilized) and GMRES method were tested with MILD preconditioner. As a smoother of the pressure correction equation, the MILU-CG is recommended rather than MILU-GMRES(k) or MILU-CGSTAB, since the MILU-GMRES(k) preconditioner has too much computation on the coarse grid compared to the MILU-CG one. As for the momentum equation, relatively cheap smoother like SIP solver. may be sufficient.