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큰 받음각을 갖는 세장형 물체 주위의 점성 유동장 수치 모사
노오현(Oh Hyun Rho),황수정(Soo Jung Hwang) 한국전산유체공학회 1995 한국전산유체공학회 학술대회논문집 Vol.1995 No.-
The compressible laminar and turbulent viscous flow on a slender body in supersonic speed as well as subsonic speed has been numerically simulated at high angle of attack. The steady and time-accurate compressible thin-layer Navier-Stokes code based on an implicit upwind-biased LU-SGS algorithm has been developed and specifically applied at angles of attack of 20, 30, 40 deg, respectively. The modified eddy-viscosity turbulence model suggested by Degani and Schiff was used to simulate the case of turbulent flow. Any geometric asymmetry and numerical perturbation have not been intentionally or artificially imposed in the process of computation. The purely numerical results for laminar and turbulent cases, however, show clear asymmetric formation of vortices which were observed experimentally. Contrary to the subsonic results, the supersonic case shows the symmetric formatian of vortices as indicated by the earlier experiments.
Numerical Simulation of Asymmetric Vortical Flows on a Slender Body at High Incidence
노오현(Oh Hyun Rho),황수정(Soo Jung Hwang) 한국전산유체공학회 1996 한국전산유체공학회지 Vol.1 No.1
The compressible laminar and turbulent viscous flows on a slender body in supersonic speed as well as subsonic speed have been numerically simulated at high angle of attack. The steady and time-accurate compressible thin-layer Navier-Stokes code based on an implicit upwind-biased LU-SGS algorithm has been developed and specifically applied at angles of attack of 20, 30 and 40 deg, respectively. The modified eddy-viscosity turbulence model suggested by Degani and Schiff was used to simulate the case of turbulent flow. Any geometric asymmetry and numerical perturbation have not been intentionally or artificially imposed in the process of computation. The purely numerical results for laminar and turbulent cases, however, show clear asymmetric formation of vortices which were observed experimentally. Contrary to the subsonic results, the supersonic case shows the symmetric formation of vortices as indicated by the earlier experiments.
김성수,김종암,노오현,홍승규,Kim Sung-soo,Kim Chongam,Rho Oh-Hyun,Hong Seung Kyu 한국전산유체공학회 2001 한국전산유체공학회지 Vol.6 No.4
본 논문은 충격파 불안정성이 나타나지 않는 충격파 안정적인 수치기법의 개발을 목표로 하고 있다. Roe의 수치기법은 유동의 수치계산에 있어 높은 정확도를 보장하지만 carbuncle 현상과 같은 충격파 불안정성이 나타나는 것으로 알려져 있다. Roe의 수치기법과 HLLE 수치기법의 수치점성을 비교하여 충격파 불안정성의 원인을 살펴보았으며, Roe의 수치기법에 나타나는 반감쇠항에 마하수의 함수인 조절함수 f와 g를 도입하여 충격파 안정성을 획득하였다. 본 논문에서 제안된 수치기법을 다양한 유동문제에 적용하여 수치기법의 충격파 안정성과 정확성을 검증하였다
점성 및 비점성 유동장 해석을 위한 BGK 수치기법의 효율적 계산
채동석,김종암,노오현,Chae, Dong-Suk,Kim, Chong-Am,Rho, Oh-Hyun 한국전산유체공학회 1998 한국전산유체공학회지 Vol.3 No.2
From the Boltzmann equation with BGK approximation, a gas-kinetic BGK scheme is developed and methods for its efficient calculation, using the convergence acceleration techniques, are presented in a framework of an implicit time integration. The characteristics of the original gas-kinetic BGK scheme are improved in order for the accurate calculation of viscous and heat convection problems by considering Osher's linear subpath solutions and Prandtl number correction. Present scheme applied to various numerical tests reveals a high level of accuracy and robustness and shows advantages over flux vector splittings and Riemann solver approaches from Euler equations.
Roe's FDS와 AUSM+ 수치기법을 이용한 무딘 물체 주위의 극초음속 유동장 해석
이준호(Joon-Ho Lee),노오현(Oh-Hyun Rho),변우식(Woo-Sik Byun) 한국전산유체공학회 1997 한국전산유체공학회 학술대회논문집 Vol.1997 No.-
The hypersonic flowfield around a blunt body was analyzed numerically with 2D Navier-Stokes equations. Roe's FDS and AUSM+ schemes were used for spatial discretization and MUSCL was used for higher order spatial accuracy. AF-ADI scheme was used for time integration. Roe's FDS needed an entropy fix to avoid the carbuncle phenomena near stagnation line. The entropy fix, however, decreased the solution accuracy in the boundary layer, so the value of entropy fix should be decreased in the boundary layer for the accurate solutions. AUSM+ is one of the hybrid flux splitting schemes which were designed to combine the accuracy of FDS and the robustness of FVS. Numerical analysis with AUSM+ didn't bring about the carbuncle phenomena. AUSM+ could show the accurate solutions in the boundary layer without any other boundary layer corrections.