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복부대동맥류의 직경비에 따른 정상유동 및 맥동유동에 관한 수치적 연구
모정하,박상규,Moh, Jeong-Hah,Park, Sang-Kyu 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.7
The objective of the present study was to investigate the characteristics of flow and wall shear stress under steady and pulsatile flow in the aneurysm. The numerical simulation using the software were carried out for the diameter ratios ranging from 1.5 to 3.0, Reynolds number ranging from 900 to 1800 and Womersley number, 15.47. For steady flow, it was shown that a recirculating vortex occupied the entire bulge with its core located closer to the distal end of the bulge and the strength of vortex increased with increase of the Reynolds number and diameter ratio. The position of a maximum wall shear stress was the distal end of the aneurysm regardless of the Reynolds number and diameter ratios. For the pulsatile flow, a recirculating flow at the bulge was developed and disappeared for one period and the strength of vortex increased with the diameter ratio. The maximum values of the wall shear stress increased in proportion to the diameter ratio. However, the position of a maximum wall shear stress was the distal end of the aneurysm regardless of the diameter ratios.
농기계용 스파크 점화기관의 효율적 냉각방법에 대한 수치적 연구
모정하 圓光大學校 環境建設硏究所 1992 環境建設論文集 Vol.1 No.-
3-D, steady, turbulent, forced convection in the longitudinal fins, which are attacted on the spark-ignition engine, is numerically investigated. The influence with variation of fin height and fin width is considered on the heat transfer at the fin surface. Results are presented for 5 geometries including the local Nusselt number. The prediction indicates that efficiency of cooling appears to be good with height of fin becoming smaller and width of fin narrower.
맥동 유동에서 복부 대동맥류의 직경비에 따른 유동 및 벽면전단응력 해석
모정하 대한의용생체공학회 2002 의공학회지 Vol.23 No.3
일정한 주기를 갖는 맥동유동에 대하여 혈관이 확장될 때 나타나는 동맥류 내부에서의 유동 및 벽면전단응력의 특성을 2차원적으로 고찰하였다. 상용 소프트웨어를 이용하여 직경비 1.5. 2.0 및 2.5 그리고 Womersley 수 15.47에 대한 복부대동맥내의 유동 현상을 수치해석하였다. 해석결과 동맥류 상단부에서 형성된 재순환유동은 시간의 흐름에 따라 생성과 소멸을 반복하였고. 시간이 3.19초인 경우, 동맥류 입구부 상단 근처에서 매우 미약한 재순환유동이 발달하고 있음을 예상할 수 있었다. 그리고 직경비가 증가할수록 동맥류 말단부에서 전단응력의 변화의 폭이 증가하였고 최대 전단응력의 값도 증가하는 것을 알 수 있었다. 그러나 최대 벽면전단응력의 발생 위치는 직경비의 변화와 거의 무관하였으며 동맥류 말단부 근처 (z : 35mm)에서 발생하였다 The objective of the present study was to two-dimensionally investigate the characteristics of flow and wall shear stress under pulsatile flow in the aneurysm which is a local dilatation of the blood vessel for pulsatile flow. The numerical simulation using the commercial software were carried out for the diameter ratios(ratio of maximum diameter of aneurysm to the diameter of blood vessel) ranging from 1.5 to 2.5 and Womersley number, 15.47. It was shown that a recirculating flow at the bulge was developed and disappeared for one Period and the strength of vortex increased with the diameter ratio Especially. at time of 3.19s. the very weak recirculating flow was developed at the left upper sites of the aneurysm. The maximum values of the wall shear stress increased in Proportion to the diameter ratio. However. the Position of a maximum wall shear stress was the distal end of the aneurysm(z = 35mm) regardless of the diameter ratios.
경사진 원형관에서 표면장력과 중력으로 구동되는 비뉴턴유체(Casson 모델)의 지배방정식 개발
모정하 한국기계기술학회 2019 한국기계기술학회지 Vol.21 No.2
This paper presents the theoretical analysis for the flow driven by surface tension and gravity force in an inclined circular tube. The previously developing equation for Power-Law model is a simple ordinary differential type. A governing equation is developed for describing the displacement of a non-Newtonian fluid(Casson model) that continuously flows into a circular tube by surface tension, which represents a second-order, nonlinear, non-homogeneous, and ordinary differential form. It was found that the theoretical predictions of the governing equation were in good agreement with the results for considering the Newtonian model.
모정하 원광대학교 생산 및 자동화기술연구소 1994 생산.자동화기술연구소논문집 : 원광대 Vol.- No.1
Analysis no the phase change heat transfer in a staggered tube bank was carried out. Governingequations were transformed with the time dependent boundary-fitted coordinate system, and discretized with the power-law scheme. The interface position, molten volume fraction and the local Nusselt numbers around the cylinder surface were obtained as a function of time for various shape factors. The calculated results show that the melting rate increases with decrease of shape factor and the local Nusselt numbers around a cylinder surface decrease toward the lower part.