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굴곡이 있는 자유표면을 가진 Liquid Bridge에서의 열모세관 대류
심복철,A.Zebib,김우승 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Thermocapillary convection in differentially heated liquid bridge is investigated by two-and three-dimensional numerical simulations. The non-deformable free surface is either flat or curved as determined by the fluid volume and the Young- Laplace equation. With the Prandtl numbers of 1 and 4 and a flat surface, our computed results for onset of oscillations are in good agreement with linear theory. Convection is steady and axisymmetric at sufficiently low values of the Reynolds number with either flat or curved surfaces. It is found that only steady convection is possible at any Reynolds number in strictly axisymmetric computations. Transition to oscillatory three-dimensional motions occurs as the Reynolds number increases beyond a critical value dependent on the Prandtl number and liquid volume. Rotating waves with wavenumbers of 1 or 2 are observed.
심복철(Bok-Cheol Sim),김우승(Woo-Seung Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Thermocapillary convection in an open cylindrical annulus heated from the inside wall is investigated<br/> by two-dimensional numerical simulations. The deformable free surface is obtained as a solution of the<br/> coupled transport equations at fixed Prandtl and aspect ratio. Only steady convection can be realized in<br/> this axisymmetric computations with either non-deformable or deformable surfaces. Dynamic free-surface<br/> deformations do not induce transitions to oscillatory convection even at large Reynolds numbers. Free<br/> surfaces are convex near the cold wall due to the stagnation point, and concave near the hot wall. Free<br/> surface deformation increases with increasing Ca at a fixed Re. Two peaks appear at the free surface<br/> with low Re, while additional ripples, four peaks, occur at larger Re. Thermocapillary convection in the<br/> open annulus interior is insensitive to variations in Ca.
겉보기 열용량법을 이용한 합금의 레이저 융용풀에서의 열 및 유동해석
김우승,심복철,임익태 漢陽大學校 工學技術硏究所 1997 工學技術論文集 Vol.6 No.1
An apparent capacity method is employed to solve numerically transient and steady state laser melting emblem of alloy. Momentum equations are solved in the liquid and mushy zones by using the SOLA-VOF algorithm. Using a laser with a top-hat profile, a wide range of studies are performed for steel. The streamline plots show the existence of rotating cell in the molten pool. It is found that the shapes of pool, the distributions of surface velocity and surface temperature are quite different from the case without convection effect in the mushy zone.
굴곡의 표면을 가진 금속의 레이저 용융에 대한 열 및 유체유동 해석
김영득(Young-Deuk Kim),심복철(Bok-Cheol Sim),김우승(Woo-Seung Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Laser melting problems with deformed substrates are investigated by axisymmetric numerical simulations.<br/> Source-based method is used to solve the energy equation, and the momentum equations are solved in the<br/> liquid domain with SIMPLER algorithm. Using a laser beam with a top-hat heat flux distribution, this study is<br/> performed to examine the effect of surface deformation, beam power density and surface tension force on the<br/> melt pool during laser melting. Surface temperature decreases with increasing surface deformation, while<br/> surface velocity increases. It is found that surface deformation, beam power density and surface tension force<br/> have a very significant effect on heat transfer and fluid flow during laser melting.