• Journal of the korean Society of Automotive Engineers
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• v.6 no.2
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• pp.1-6
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• 1984

복잡한 연소과정의 예측을 위한 이론적인 연구는 Gosman, Spalding, Patankar등의 수치해석방 법을 이용하여 진행된 것들이 많다. 현재 이분야에 응용되는 일반적인 Program으로는 Boundary Layer Type의 방정식을 이용한 One-Dimensional Program (GENMIX 4, Revised GENMIX) 등이 있으나 Parabolic Type이므로 주방향에 수직된 방향으로 동일한 값이 2개 이상 존재할 수 있는 Elliptic현상을 설명하기에는 어려움이 있다. 그러므로 비록 기억용량(Computation Storage) 및 계산시간(Running Time)에 불리한 점이 있기는 하나 Elliptic상황을 해석해야만 할 경우가 있다. 본 해설은 Patankar의 Elliptic "SIMPLE" Program을 연소 해석과정에 이용되는 방법을 간단한 연소과정의 예로서 설명하는 것으로 연소과정의 연구보다도 Program의 응용성에 중점을 두었다. 따라서 실제의 물리적인 연소 mechanism에서 많은 가정을 도입하여 문제를 단순화 시켰으며 실제의 연소문제에 충분한 접근을 위해서는 turbulence-modeling과 radiation heat flux가 본 해설에 덧붙여져서 논의되어야 한다. 논의되어야 한다.

• Journal of the Korean Society of Visualization
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• v.5 no.2
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• pp.56-63
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• 2007

Flow visualization and aerodynamic characteristics of delta wings with two different leading edge geometries are investigated by PIV system and wind tunnel balance when the Reynolds number is about based on the freestream velocity and the root chord length. Delta wing models have 65-deg swept angle, and the leading edge shapes are divided into round- and sharp- type. The experimental results indicated that the leading-edge vortex strength and aerodynamic coefficient in the round leading edge are stronger and more, respectively than those in the sharp one. Therefore the flow interactions between vortices and the boundary layer are more desirable or more rapidly swirled in the round-type leading edge.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.371-382
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• 2001

The recognition of such natural wave guides as plates, rods, hollow cylinders, multi-layer structures or simply an interface between two materials combined with an increased understanding of the physics and wave mechanics of guided wave propagation has led to a significant increase in the number of guided wave inspection applications being developed each year. Of primary attention Is the ability to inspect partially hidden structures, hard to access areas, and teated or insulated structures. An introduction to some physical consideration of guided waves followed by some sample problem descriptions in pipe, ice detection, fouling detection in the foods industry, aircraft, tar coated structures and acoustic microscopy is presented in this paper. A sample problem in Boundary Element Modeling is also presented to illustrate the move in guided wave analysis beyond detection and location analysis to quantification.

• Applied Science and Convergence Technology
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• v.27 no.2
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• pp.23-25
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• 2018

With respect to the electrode structure and the discharge characteristics, the atmospheric pressure plasma sheet of a thin polyimide film is introduced in this study; here, the flexible plasma device of a dielectric-barrier discharge with the ground electrode and the high-voltage electrode formulated on each surface of a polyimide film whose thickness is approximately $100{\mu}m$, that is operated with a sinusoidal voltage at a frequency of 25 kHz and a low voltage from 1 kV to 2 kV is used. The streamer discharge is appeared along the cross-sectional boundary line between two electrodes at the ignition stage, and the plasma is diffused on the dielectric-layer surface over the high-voltage electrode. In the development of a plasma sheet with thin dielectric films, the avoidance of the insulation breakdown and the reduction of the leakage current have a direct influence on the low-voltage operation.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.6
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• pp.72-81
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• 1991

In this study, the analytic investigation of the unsteady flow in the intake and exhaust pipes has been carried out using the method of characteristics in one direction to predict volumetric efficiency. Based on the calculated volumetric efficiency, three zone predictive analysis using Wiebe function was applied to predict the engine performance and the results were compared with experiment. Mixture in the cylinder is subdivided into three zones during combustion process in this analysis; adiabatic core zone, thermal boundary layer zone and unburned zone. In each zone, pressure, temperature and gas composition have been calculated. In conclusion, it is possible to take account of the intake and exhaust pipe tuning effect in predicting the engine performance, by the analytic solution of the unsteady flow in the pipes, and comparison of prediction with experimental results shows a good agreement on the pressure variation in the intake and exhaust pipes which has a direct influence on the volumetric efficiency and performance of the engine.

• International Journal of Aeronautical and Space Sciences
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• v.5 no.2
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• pp.9-17
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• 2004

In this paper, a small supersonic wind tunnel was designed and built to studythe flow characteristics of a supersonic impulse turbine cascade by experiment. Theflow was visualized by means of a single pass Schlieren system. The supersoniccascade with 3-dimensional supersonic nozzle was tested over a wide range ofpressure ratio. Highly complicated flow patterns including shocks, nozzle-cascadeinteraction and shock boundary layer interactions were observed.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.6
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• pp.633-640
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• 2000

The effects of structure modification of the vortex finder on the collection efficiency and pressure drop have been investigated. The pressure drop in a cyclone having the two stage vortex finder is higher than that in a conventional cyclone and increases proportionally with the increase of square of gas inlet velocity in both cases. The pressure drop of both conventional cyclone of friction resistance at the boundary layer. The collection efficiency of fine dust has been enhanced by addition of vortex finder in a conventional cyclone and gas inlet velocity showing maximum dust removal efficiency increase to 17 m/s(1.7 times of saltation velocity). Optimum size of two stage vortex finder has been induced to 13 cm I.D$\times$2.6cm Length from the results of overall dust collection efficiency. Previous models were tested for the simulation of collection efficiency of cyclone having two stage vortex finder and the Dietz model predict the similar value with experimental results of the present study.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.4
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• pp.69-76
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• 1987

A conjugate conduction-convection analysis has been made for a plate fin which exchanges heat with its fluid environment by forced convection. The analysis is based on a one- dimensional model for the plate fin whereby the transient heat conduction equation for the fin is solved simultaneously with the conservation equations for mass, momentum, and energy in the fluid boundary layer adjacent to the fin. The forced convection heat transfer coefficient is not specified in advance but is one the results of the numerical solutions. Numerical results of the overall heat transfer rate, the local heat transfer coefficient, the local heat flux, the fin efficiency and the fin surface temperature distribution for Pr=0.7 are presented for a wide range of operating conditions.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.2
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• pp.34-40
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• 2008

The aeroelastic analyses for several wing models were performed using the transonic small-disturbance (TSD) equation, which is very efficient, to consider the aerodynamic nonlinearities in the transonic region. For more accurate aerodynamic analysis of airfoil and wing models with shock waves, the viscous equations based on the Green's lag-entrainment equation of boundary-layer effects were coupled with the TSD equation in the transonic region. Finally the aeroelastic characteristics of wing models were investigated through comparisons of the aeroelastic analysis results for wing models considering the change of a thickness of the airfoil section. Moreover, the results of the aeroelastic analysis using the coupled TSD equation with the viscous equations were compared with those using the TSD equation for several wing models.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.20 no.4
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• pp.309-332
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• 2016

Finite element method has been applied to solve the fundamental governing equations of natural convective, electrically conducting, incompressible fluid flow past an infinite vertical plate surrounded by porous medium in presence of thermal radiation, viscous dissipation, Soret and Dufour effects. In this research work, the results of coupled partial differential equations are found numerically by applying finite element technique. The sway of significant parameters such as Soret number, Dufour number, Grashof number for heat and mass transfer, Magnetic field parameter, Thermal radiation parameter, Permeability parameter on velocity, temperature and concentration evaluations in the boundary layer region are examined in detail and the results are shown in graphically. Furthermore, the effect of these parameters on local skin friction coefficient, local Nusselt number and Sherwood numbers is also investigated. A very good agreement is noticed between the present results and previous published works in some limiting cases.