• 천문학논총
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• 제9권1호
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• pp.21-38
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• 1994

We have developed a cylindrical mixing layer model of a stellar jet including cooling effect in order to understand an optical emission mechanism along collimated high velocity stellar jets associated with young stellar objects. The cylindrical results have been calculated to be the same as the 2D ones presented by Canto & Raga(1991) because the entrainment efficiency in our cylindrical model has been obtained to be the same value as the 2D model has given. We have discussed the morphological and physical characteristics of the mixing layers by the cooling effect. As the jet Mach number increases, the initial temperature of the mixing layer goes high because the kinetic energy of the jet partly converts to the thermal energy of the mixing layer. The initial cooling of the mixing layer is very severe, changing its outer boundary radius. A subsequent change becomes adiabatic. The number of the Mach disks in the stellar jet and the total radiative luminosity of the mixing layer, based on our cylindrical calculation, have quite agreed with the observations.

• 한국전산유체공학회지
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• 제15권4호
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• pp.53-59
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• 2010

Preliminary design of a ground plate, a device installed close to the aircraft model for wind tunnel test to simulate the ground effect, was performed by a numerical simulation. A two-dimensional numerical study was performed initially to decide the optimal leading edge and flap configurations. Then, three-dimensional studies were conducted to decide the optimal flap deflection angle for pressure distribution reduction since the plate and the plate supporting system generate static pressure difference between the upper and lower flow regions. Three-dimensional simulation additionally studied the effect of the clearance between the plate and the wind tunnel side wall. For the efficiency of computation, half model was simulated and a symmetric boundary condition was applied on the center plane. Based on the preliminary design, a ground plate was designed, manufactured and tested at the Korea Aerospace Research Institute(KARI) wind tunnel. The measured pressure differences versus flap deflection angle agreed well with the predicted results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.957-962
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• 2004

This paper deals with the free vibration analysis of beam-columns resting on Pasternak foundation by the Differential Quadrature Method. Based on the differential equation subjected to the boundary conditions, adopted from the open literature, which governs the free vibrations of such member, this equation is applied to the Differential Quadrature Method. For computing natural frequencies, the numerical procedures are developed by QR Algorithm, in which the Chebyshev-Gauss-Lobatto method is used for choosing the grid points. The numerical methods developed herein for computing natural frequencies are programmed in FORTRAN code, and all solutions obtained in this study are quite agreed with those in the open literature.

• 대한기계학회논문집
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• 제16권2호
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• pp.336-347
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• 1992

The three dimensional inviscid transonic cascade flow was investigated numerically, incorporation a four stage Runge-Kutta integration method proposed by Jameson. Time marching to the steady state was accelerated by using optimum time step and enthalpy damping. In describing the boundary conditions at inlet and outlet, Riemann invariants are considered. By adding a second and a fourth order artificial viscocities, the numerical instability due to the propagation of undamped disturbance or the rapid change of state near the shock has been prevented. The numerical results for are bump cascade, cambered two dimensional turbine cascade and three dimensional stator cascade agreed reasonably well with previous results. It has been known that the accuracy of the solution depended a lot on the modeling of the leading or trailing edge.

• 센서학회지
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• 제7권1호
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• pp.9-16
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• 1998

본 논문에서는 구형의 수중 구조체에 평면 음향파가 입사될 경우에 발생하는 산란파 음압의 크기와 방향성이 3차원적으로 어떻게 분포되는 지 살펴보고 자 한다. 이를 위한 수치해석적 방법으로 결합형 유한요소-경계요소(FE-BE) 기법을 개발하였다. 이 같은 구형 모델의 수치해석적 결과를 기존의 이론적 해답과 비교하여 본 연구에서 개발한 결합형 FE-BE 기법의 타당성을 검증하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.217-222
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• 1997

Free vibration analysis of a Core Support Barrel shell structure is studied through experimental and finite element analysis methods. The structure is considered to be a thick shell with the ratio of thickness to radius 3/10. Finite element model is established by solid model with brick elements. Modal analyses are performed with respect to the various ratios of thickness to radius with clamped-free and free-free boundary conditions. Experimental test is done to find out how well the results are agreed with those of analysis. The comparison of the results from experiment and analysis shows a good agreement between them in general.

• Journal of Biosystems Engineering
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• 제16권3호
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• pp.290-297
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• 1991

For the efficient utilization of the solar thermal energy to overcome the time gap between to supply and demand, an efficient heat storage technique, especially high density-latent-heat storage system, is necessary. In this study, the performance of a panel type latent heat storage equipment during heat discharging process was analyzed theoretically and experimentally. In order to find out the performance of the system, computer simulation programs were developed by finite difference method. The governing equations were constructed by two dimensional heat conduction model with moving boundary. The results of the experimental and the theoretical analysis were reasonably well agreed. The efficiencies of the double pipe type and the panel type latent heat storage equipment were compared.

• Korean Journal of Geomatics
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• 제2권2호
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• pp.107-113
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• 2002

On this study, it was applied that the method of Coastline extracting by aerial photogrammetry so as to extract the coastline using the method of RTK GPS/GLONASS. The observed area is Gwanganri beach that is located in Pusan and it was observed according to high wave of scar when the approximate highest high water and it was surveyed according to that the boundary line connecting to sea water surface at random time-zone. Observation analysis was used digital map of 1:1,000 and compared coastline that was converted tide with coastline of high tide. So this conclusions was agreed with converted coastline and high tide coastline.

• 설비공학논문집
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• 제1권1호
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• pp.9-20
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• 1989

This paper presents an analysis to predict thermal behaviors of water in ice storage tank during the coldness release process. To deal with complicated transient phenomena due to ice-water phase change and the density inversion, a theoretical model which consists of initial perfectly mixed, stratified and thermal diffusion state was introduced and a criterion on the growth of thermal boundary layer was developed. The analysis includes considerations on the type of ice-making heat exchanger, refrigerator on/off and tank arrangement. Also, discussions on the various parameters and operating conditions which have influence on the performance of the system were made. Finally, simulated results were shown, which agreed with experiments in trends reasonably.

• 설비공학논문집
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• 제3권4호
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• pp.215-221
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• 1991

Laminar film condensation of a saturated vapor in forced flow over a flat plate is analyzed by using integral method. Laminar condensate film is so thin that the inertia and thermal convection terms in liquid flow can be neglected. Approximate solutions for water are presented and well agreed with the similarity solutions over the wide range of physical parameter, Cp1(Ts-Tw)/Pr.hfg. For the strong condensation case, it is found that magnitude of the interfacial shear stress at the liquid-vapor interphase boundary is approximately equal to the momentum transferred by condensation, i.e., ${\tau}_i{\simeq}\dot{m}(U_O-U_i)$.