• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.245-250
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• 2008

For simulation of a wing unfolding motion for the various aerodynamic conditions, equation governing unfolding motion and moments applying to the unfolding wing were modelled. Aerodynamic roll moment consists of the static roll moment and the damping moment, which were obtained through wind tunnel tests and numerical analyses respectively. Panel method was used to compute the roll damping coefficient with twisted wing, whose deflection angle was equivalent to angle of attack due to the deployment motion. Roll damping coefficient is a function of angle of attack, sideslip angle, and deployment angle but not of angular velocity of deployment. Simulation with aerodynamic damping model gave more similar deployment time compared to wing deployment test results.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.562-567
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• 2000

The Impingement of a weak shock wave discharged from the open end of a shock tube upon a flat plate was investigated using shock tube experiments and numerical simulations. Harten-Yee Total Variation Diminishing method was used to solve axisymmetric, unsteady, compressible flow governing equations. Experiments were carried out to validate the present computations. The effects of the flat plate and baffle plate sizes on the impinging flow field over the flat plate were investigated. Shock Mach number was vaned in the range from 1.05 to 1.20. The distance between the plate and shock tube was changed to investigate the effect on the peak pressure. From both the results of experiments and computations we obtained a good empirical equation to predict the peak pressure on the flat plate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.7
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• pp.877-884
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• 2001

A theoretical analysis is conducted on the Stokes flow in a narrow channel. A vertical fin is mounted on the bottom plate and the flow is induced by uniformly sliding top plate. The governing harmonic equation was solved in the transformed ζ-plane, which is obtained by applying conformal mappings to the physical plane. By using well-known transformation technique, closed-form expressions for velocity and skin frictional stress on the top and bottom plates were obtained.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.9
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• pp.2909-2915
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• 1996

Precise and accurate pressure measurements are obtained using deadweight piston gauges. Pressure distribution and elastic distortion in the piston-cylinder unit are the leading factors in determination of effective area. The distortion depends upon the pressure distribution in the clearance between piston and cylinder and those are coupled each other. Considering the viscosity pressure relation of oil and governing flow equation in the clearance, a new numerical iterative algorithm is developed. The disagreement between the monotonous and sharp pressure profiles is an indication that the pressure profile will be different for each piston and cylinder unit due to material variances.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1498-1507
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• 1996

This paper presents a robust control of a smart flexible structure featured by a piezofilm actuator characterizing its light weght and quick response time. A mathematical governing equation for the proposed structure is derived by employing Hamilton's principle and a state space control model is subsequentrly obtained through modal analysis. Uncertain system parameters such as frequency variation are included in the control model. A sliding mode control theroy thich has inherent robustness to systme uncertainties is adopted to design a tracking controller for the peizofilm actuator. Using the output informaiton from the tip deflection sensor, a full-order observer is constructed ot estimate state variables for the system. Tracking performances for desired trajectories of sinusoidal amd step functions are evaluated by undertaking both simulation and experimental works.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1789-1798
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• 1994

This paper aimed for numerical simulation of complicated gas turbine combustor with swirler. For the convenience of numerical analysis, fuel nozzle and air linear hole areas of secondary and dilution zone, which are issued to jet stream, were simplified to equivalent areas of annular type. In other to solve these problems, imaginary source terms which are corresponded to supplied fuel amount were added to those of governing equation. Chemical equilibrium model of infinite reaction rate and $k-{\epsilon}-g$ model with the consideration of density fluctuation were applied. As the result, swirl intensity contributed to mixing of supplied fuel and air, and to speed up the flame velocity than no swirl condition. Temperature profiles were higher than experimental results at the upstream and lower at the downstream, but total energy balance was accomplished. As these properties showed the similar trend qualitatively, simplified simulation method was worth to apply to complicated combustor for predicting combustion characteristics.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.3
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• pp.1-9
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• 1994

The transient temperature distribution of materials during upsetting forming is very important for quality of upsetted workpiece and understanding the thermal characteristics of upsetting is essential for optimum control of the forming. In this paper it is shown that the governing equation of heat transfer for axi-symetric body can be derived from minimizing a functional, and from this theory, formulation of analysis by the finite element method is presented. It is also shown that the thermal contact resistance between two bodies can be represented by equivalent coefficient of heat conductivity. Some examples of calsulated transient temperature distributions by the computer program diveloped from the theory presented in this paper are given in graphic forms. It is proven that the results calculations are very plausible.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.3
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• pp.409-415
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• 2003

The purpose of this paper is to develop the 2-Dim Lagrangian Hydrocode for the analysis of large deformations of solids with implementation of the contact algorithm. First, th e governing equations are discretized into a system of algebraic equations. For more accurate and robust contact force computation. the defense node contact algorithm was adopted and implemented. For the verification of the code developed, two cases are carried out; the Taylor-Impact test and two bodies impact. The von -Mises criterion is implemented into the code with the Shock equation of state. The simulation results show a good agreement compared with the published experimental data and results from the commercial code. It is necessary to implement several material models and failure models for applications to different impact and penetration problems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.3
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• pp.319-327
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• 1983

The thermal diffusivity one of the series of standard pieces for spark test are determined by the flash method. The standard pieces are composed with carbon steels, structural carbon steels, alloy steels and high speed tool steels. In order to compute the thermal conductivity of the standard pieces, their specific heats are measured by a differential scanning calorimeter. The thermal conductivities are calculated from the data of specific heat, density and thermal diffusivity. To increase the accuracy of data for the thermal diffusivity by data reduction excursion method in the flash method, the governing heat diffusion equation, which is closely described experimental conditions with the finite pulse and the heat loss from the sample surfaces, is solved. In this analysis an integral transform is used.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1919-1922
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• 2003

Bypass anastomosis are frequently adopted for surgical treatments. After the bypass grafting, the bypass artery is often occluded due to restenosis and/or anastomotic neointimal fibrous hyperplasia phenomena. Optimal coronary bypass anastomosis should be investigated to improve the patency for the arterial bypass techniques. The objective of this study is to investigate the influence of bypass with sequential bypass effects in the stenosed coronary artery. Numerical analyses are focused on the understanding of the flow patterns for different sequential anastomosis techniques. Blood flow field is treated as two-dimensional incompressible laminar flow. The finite volume method is adopted for discretization of the governing equations. The Carreau model is employed as the constitutive equation for blood. To find the optimal sequential bypass anastomotic configurations, the mass flow rates at the outlet of different models are compared quantitatively.