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서정천(J.-C. Suh) 한국전산유체공학회 1998 한국전산유체공학회 학술대회논문집 Vol.1998 No.-
As an alternative for solving the incompressible Navier-Stokes equations) we present. a vorticity integro-differential formulation for vorticity) velocity and pressure variables. One of the most difficult problems encountered in the vorticity-based methods is the introduction of the proper value of vorticity or vorticity flux at the solid surface. A practical computational technique toward solving this problem is presented in connection with the coupling between the vorticity and the pressure boundary conditions. Numerical schemes based on an iterative procedure are employed to solve the governing equations with the boundary conditions for the three variables. A finite volume method is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savart integral derived from the mathematical vector identity. Green)s scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well-established for potential flow analysis. The calculated results with the present method for two test problems are compared with data from the literature in order for its validation. The first. test problem is one for the two-dimensional square cavity flow driven by shear on the top lid. Two cases arc considered here: (i) one driven both by the specified non-uniform shear on the top lid and by the specified body forces acting through the cavity region, for which we find the exact solution, and (ii) one of the classical type (I.e.) driven only by uniform shear). Secondly, the present method is applied to deal with the early development of the flow around an impulsively started circular cylinder.
서정인(J . I . Suh),장승필(Sung Pil Chang),김호경(H. K. Kim),박정일(J. I. Park) 한국강구조학회 1994 韓國鋼構造學會誌 Vol.6 No.2
Hangers of self-anchored suspension bridges are generally installed after temporarily supporting girders. Hangers are installed with initial tension, then hangers can be exposed to greater than that of final stage during the sequence of construction. Therefore it is required that the tension of hangers should be within the allowable capacity. This study presents the nonlinear analysis method to simulate the construction sequence of self-anchored suspension bridge. The tension variation of hangers according to the sequence and method of construction is studied.
서정천(J. C. Suh) 한국전산유체공학회 1998 한국전산유체공학회지 Vol.3 No.1
A vorticity-based method for the numerical solution of the two-dimensional incompressible Navier-Stokes equations is presented. The governing equations for vorticity, velocity and pressure variables are expressed in an integro-differential form. The global coupling between the vorticity and the pressure boundary conditions is fully considered in an iterative procedure when numerical schemes are employed. The finite volume method of the second order TVD scheme is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savarl integral. The Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well established for potential flow analysis. The present formulation is validated by comparison with data from the literature for the two-dimensional cavity flow driven by shear in a square cavity. We take two types of the cavity flow: (i) driven by non-uniform shear on top lid and body forces for which the exact solution exists, and (ii) driven only by uniform shear (of the classical type).
서정천(J. C. Suh) 한국전산유체공학회 1998 한국전산유체공학회지 Vol.3 No.1
A vorticity-based method for the numerical solution of the two-dimensional incompressible Navier-Stokes equations is presented. The governing equations for vorticity, velocity and pressure variables are expressed in an integro-differential form. The global coupling between the vorticity and the pressure boundary conditions is fully considered in an iterative procedure when numerical schemes are employed. The finite volume method of the second order TVD scheme is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savarl integral. The Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well established for potential flow analysis. The present formulation is validated by comparison with data from the literature for the two-dimensional cavity flow driven by shear in a square cavity. We take two types of the cavity flow: (i) driven by non-uniform shear on top lid and body forces for which the exact solution exists, and (ii) driven only by uniform shear (of the classical type).
서정,한유희,김정오,이영신,Suh, J.,Han, Y.H.,Kim, J.O.,Lee, Y.S. 대한용접접합학회 1996 대한용접·접합학회지 Vol.14 No.1
The maximum butt-joint gap size in $CO_2$ laser beam welding of SAPH steel plates with different thicknesses and its bending formability were studied. In the range of the gap size$\geq$0.1mm, the optimal butt welding speed was faster than that of no gap (air gap) condition. This behaviour was independent on the difference of thickness at any combination. Also, the allowable gap size in steel plates with different thicknesses was larger than with same thicknesses. In the range of $T/T_0$(bead shape) $\geq$ 0.8, good bending formability was obtained at any combination of thickness. The formability was improved by reducing the hardness in weld bead using pre-heating process. Finally, FEM result of the laser beam welded underframe with different thicknesses was compared to that of the conventional spot welded underframe.
스크린 메쉬형 가변전열 히트파이프에서 NCG양에 따른 작동특성 변화
서정세(J.S. Suh),박영식(Y.S. Park),강창호(C.H. Kang),정경택(K.T. Chung),박기호(K.H. Park),이기우(K.W. Lee) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
Experimental study is performed to investigate the effect of heat load and operating temperature on the thermal performance of a heat pipe with screen mesh wick. The heat pipe was designed in 200 screen meshes, 500㎜ length and 12.7㎜ O.D tube of copper, water as working fluid(4.8g) and nitrogen as non-condensible gas(NCG). The heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Experimental data of axial wall temperature distribution is presented for heat transport capacity, the temperature of cooling water of condenser, inclination angle, and operating temperature. For the results from this study, it is found that, for the same charging mass of working fluid, the initial operating temperature and the overall wall temperatures of heat pipe are higher for NCG charging mass of 5.0×10??㎏ and 3.4×10??㎏, than that of 1.0×10??㎏.
혼합반도체 시스템에서의 광화학적 수소제조 : Cds-WO₃RuO₂, CdS-TiO₂
서정기(J . K . Suh),허귀석(G . S . Heo) 한국수소및신에너지학회 1993 한국수소 및 신에너지학회논문집 Vol.4 No.2
Hydrogen production in visible light with the following semiconductor systems, CdS-WO₃, CdS-TiO₂, have been investigated in the presence of redox catalyst(Pt, RuO?). MeOH, EtOH, isopropanol, sulfide/sulfite mixture, lactic acid were used as sacrifical reagents. The optimal condition for H? evolution was found to be in agueous lactic acid media for CdS-WO₃/RuO₂. The photochemical efficiency for this system was 1.05% and the H? evolution rate was 26.5ml/min. at 6.07X10<sup>-5</sup> einstein/sec photon rate