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초음속 기저부 유동에서 ${\kappa}-{\varepsilon}$ 난류 모델에 대한 와점성 계수의 영향
박수형,사정환,김지웅,권장혁,김창주,Park, Soo-Hyung,Sa, Jeong-Hwan,Kim, Jee-Woong,Kwon, Jang-Hyuk,Kim, Chang-Joo 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.3
A supersonic base flow is computed to investigate the effect of the eddy viscosity coefficient to the linear ${\kappa}-{\varepsilon}$ turbulence models. Slight modifications to the eddy viscosity coefficient, which are based on the realizability condition, are given to the Launder-Sharma turbulence model so that present models satisfy the realizability condition. Numerical results for supersonic base flow show that turbulence models with the weaky-nonlinear eddy viscosity coefficient can lead to reasonable enhancements in the prediction of the velocity and turbulent kinetic energy profiles.
박수형(Soo Hyung Park),권장혁(Jang Hyuk Kwon),유영훈(Yung Hoon Yu) 한국항공우주학회 2006 韓國航空宇宙學會誌 Vol.34 No.11
축대칭 발사체의 동적 감쇠계수를 계산하기 위한 정상 예측 방법을 제안한다. 관성좌표계에서 영스핀 코닝 운동을 사용한 정상 해법을 적용하기 위해서는 점성유동 해석이 필수적으로 이루어져야 한다. 제안된 방법을 회전발사체에 적용하여 피칭모멘트와 피치감죄 모멘트계수를 계산하였다. 결과는 포물형 Navier-Stokes 예측 결과, 실험결과, 비정상 예측 결과와 잘 일치함을 확인하였다. 또한, secant-ogive-cylinder 계열 발사체에 대한 정적 및 동적 계수의 축방향 생성과정을 살펴봄으로써 후방동체의 형상으로 인한 유동 변화가 동적 안정성에 미치는 영향을 고찰하였다. A steady prediction method is presented to compute dynamic damping coefficients for axisymmetric projectiles. Viscous flow analysis is essential to the steady method using a zero-spin coning motion in the inertial coordinate frame. The present method is applied to compute the pitching moment and the pitch-damping moment coefficients for the Army-Navy Spinning Rocket. The results are in good agreement with the parabolized Navier-Stokes data, range data, and unsteady prediction data. Predictions for Secant-Ogive-Cylinder configurations are performed to investigate effects of afterbody geometries. To investigate the geometrical effect and flow physics, the longitudinal developments of the coefficients are examined in detail.
박수형(Soo Hyung Park),성춘호(Chun-ho Sung),권장혁(Jang Hyuk Kwon),이승수(Seungsoo Lee) 한국전산유체공학회 2002 한국전산유체공학회지 Vol.7 No.4
An efficient implicit multigrid method is presented for the Navier- Stokes and k-ω turbulence equations. Freezing and limiting strategies are applied to improve the robustness and convergence of the multigrid method. The eddy viscosity and strongly nonlinear production terms of turbulence are frozen in the coarser grids by passing down the values without update of them. The turbulence equations together with the Navier-Stokes equations, however, are consecutively solved on the coarser grids in a loosely coupled fashion. A simple limit for k is also introduced lo circumvent slow down of convergence. Numerical results for the unseparated and separated transonic airfoil flows show that all computations converge well without any robustness problem and the computing time is reduced to a factor of about 3 by the present multigrid method.
HLLE+와 LU-AF를 이용한 극초음속 화학적 비평형 유동장 해석
박수형(Soo-Hyung Park),권장혁(Tang Hyuk Kwon) 한국전산유체공학회 2000 한국전산유체공학회지 Vol.5 No.2
A robust Navier-Stokes code has been developed to efficiently predict hypersonic flows in chemical nonequilibrium. The HLLE + flux discretization scheme is used to improve accuracy and robustness of hypersonic flow analysis. An efficient LU approximate factorization method is also used to solve the flow equations and species continuity equations in fully coupled fashion to implicitly treat stiff source terms of chemical reactions. The HLLE+ scheme shows lower grid dependency for the wall heating rates than other schemes. The developed code has been used to compute chemical nonequilibrium air flow through expanding hypersonic nozzle and past two and three dimensional blunt-nosed bodies. The results are in good agreement with existing numerical and experimental results.
양측 슬와동맥 혈전 폐색증에서 성공적인 내혈관 치료 1예
박수형 ( Soo Hyung Park ),장원영 ( Won Young Jang ),현학준 ( Hak Jun Hyun ),최성지 ( Seong Ji Choi ),김민정 ( Min Jung Kim ),나승운 ( Seung-woon Rha ) 대한내과학회 2018 대한내과학회지 Vol.93 No.4
본 증례에서는, 좌심실박출률이 저하된 확장심근병과 관상동맥 질환이 있는 환자에서 심첨부의 혈전이 심장초음파로 확인이 되었고, 이것이 밀초동맥색전증의 원인으로 생각되었다. 이후 혈관조영술 및 혈관내 스텐트를 통하여 기계적혈전흡인술, 풍선확장술 그리고 동맥내 혈전용해제 투여를 한 후 혈관 폐색 부위의 성공적인 재개통을 이룰 수 있었다. 전신적인 혈전색전증의 일환으로 다발성, 양측성 슬와동맥혈전색전증이 발생한 것은 비교적 드문 경우이며, 이러한 상황에서 수술이나 Fogarty의 풍선 카테터를 이용한 혈전제거술을 하지 않고 경피적 중재 시술을 통하여 효과적으로 치료한 경우로 이에 보고하는 바이다. The popliteal artery is a relatively short vascular structure, but acute occlusion can decrease blood flow into the lower extremities and cause subsequent critical limb ischemia, amputation, and even mortality. Further, peripheral artery disease patients frequently have combined cardio-cerebrovascular disease. Here, we report a rare case of sudden bilateral thrombotic total occlusion in the popliteal arteries of a patient with dilated cardiomyopathy and left ventricular thrombi. This patient has been successfully managed by endovascular therapy and subsequent intra-arterial thrombolytic therapy. (Korean J Med 2018;93:393-397)