• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1835-1842
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• 2007

The purpose of this paper describes the changes of TGV & ICE series' nose shape by increasing train speed and according to the periodical characteristics. As the speed increases, the length of the nose shape trends to lengthen longer. But the nose shape length does not increase as speed improves by optimized nose shape to reduce aerodynamic drag and micro-pressure wave in tunnels. TGV & ICE series' nose shape can be classified into Advanced paraboloid type, Shape-nosed type, Organic double-edged type and Flat-nosed type by the advance research(the changes of Shinkansen vehicle' nose shape) of high speed railway. Because it trends to be diversified and characterized more and more. This paper analyzed and introduced as TGV & ICE series' nose shape by top 2 nation (Germany, France) and high speed railway in the past years(1980-2007) for their railway design trends by new positioning(Advance research).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1386-1392
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• 2000

This paper presents a new prediction method of radiated noise from grille of the airconditioning appliance. Laminar vortex sheddings behind a circular cylinder are simulated by solving two dimensional unsteady incompressible Navier-Stokes equation. The Finite Elements Method(FEM) and unstructured grid generation technique are applied to solve, the unsteady lift/drag coefficients are obtained to compute far-field noise using Lighthill's acoustic analogy. Grille is divided into some cylinder segments, and radiated noise from grille is obtained by summing noise generated from each segment. The effects of changing cross section of cylinder and grille geometry are studied. And sound pressure levels radiated from typical H-type grille are measured in KAIST anechoic wind tunnel at various inflow conditions and compared with numerical predictions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 춘계학술대회 논문집
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• pp.200-205
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• 1992

This study concerns about the orbit prediction and orbit determination of Korean future connumication satellite, called "Moogunghwa" , which will be motioned in the geo-stationary orbit. Perturbation effect on the satellite orbit due to nonspherical term, lunar and solar gravity, drag force of the atmospher, and solar radiation pressure was investigated. Cowell's method is used for orbit prediction. Orbit determination was performed by using Extended Kalman Filter which is suitable for real-time orbit determination. The result shows that the chacteristics of the satellite orbit has east-west and south-north drift. So the periodic control time and control value in the view of the periodic of error can be provided. The orbit determination demonstrated the effectiveness since the convergence performance on the positon and velocity error, and state error standard deviation is reasonable.

• Ocean Systems Engineering
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• 제10권3호
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• pp.289-316
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• 2020

In the present paper, the effect of the location of stern planes on the flow entering the submarine propeller is studied numerically. These planes are mounted on three longitudinal positions on the submarine stern. The results are presented considering the flow field characteristics such as non-dimensional pressure coefficient, effective drag and lift forces on the stern plane, and the wake flow formed at the rear of the submarine where the propeller is located. In the present study, the submarine is studied at fully immersed condition without considering the free surface effects. The numerical results are verified with the experimental data. It is concluded that as the number of planes installed at the end of the stern section along the submarine model increases, the average velocity, width of the wake flow and its turbulence intensity formed at the end of the submarine enhance. This leads to a reduction in the non-uniformity of the inlet flow to the propulsion system.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 춘계 학술대회논문집
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• pp.57-64
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• 2005

Aerodynamic characteristics of three-dimensional wings in ground effect for Aero-levitation Electric Vehicle(AEV) are numerically investigated for various fairing shapes at the junctions of 3D Wings. Numerical results show that a sizeable three-dimensional comer flow separation occurs with formation of an arch vortex at the junction of main and vertical wings, and also that this is predicted the main cause of the high lift-to-drag(L/D) reduction rate of the main wing. To avoid the comer flow separation, the main idea of this study is to reduce the cross section gradient of the comer flow tube near the trailing edge for various fairing shapes. Improvements on L/D ratios of the wings are pursued by breaking the coherence of superimposed adverse pressure gradients at the wing junction when the cross section gradient is changed slowly at the trailing edge.

• 한국전산유체공학회지
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• 제19권1호
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• pp.57-63
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• 2014

This study performed numerical analysis for the characteristics of flow-induced forces and the flow instability depending on the cross-sectional shape of the cylinder in laminar flow. To implement the cylinder cross-section, we adopted an Immersed Boundary Method with marker particles. We analyzed flow characteristics based on the radius of corner curvature. Main parameters are corner radius and Reynolds number (Re). With Re = 40, 50, 150 we calculated the flow field, drag coefficient, RMS of lift coefficient, pressure coefficient and Strouhal number in conjunction with the corner radius variation. Also, we calculated critical Reynolds number ($Re_c$) depending on the corner radius variation.

• 한국전산유체공학회지
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• 제19권2호
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• pp.8-16
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• 2014

Two-dimensional prediction capability of several analysis codes, such as XFOIL, MSES, and KFLOW, is compared and analyzed based on computational results of airfoil flows. To this end the transition transport equations are coupled with the Navier-Stokes equations for the prediction of the natural transition and the separation-induced transition. Experimental data of aerodynamic coefficients are used for comparison with numerical results for the transitional flows. Numerical predictions using the transition transport model show a good agreement with experimental data. Discrepancies have been found in the prediction of the pressure drag are mainly caused by the difference in the far-field circulation correction methods.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.622-625
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• 2008

While the research for flow over a circular cylinder has been actively carried out up to the present, it has been known that the flow has not been clarified even now. Various complex flow and aero-acoustic characteristics exist around a circular cylinder such as flow separation, wake and pressure wave propagation. In this paper, research was carried out for wake flow and aeroacoustics over a circular cylinders by using high order, high resolution techniques that are used in two dimensional aero- acoustic analysis. OpenMP parallel processing method was used. For the numerical result, the periodic characteristic of Strouhal Number due to vortex shedding was comparatively analyzed with other experiment values and two dimensional numerical results.

• 한국전산유체공학회지
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• 제10권2호
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• pp.60-68
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• 2005

For study on the unsteady wall interference effect, flows around a forced oscillating airfoil in closed test-section wind tunnels have been numerically investigated by solving compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with the Roe's flux-difference splitting and an implicit time-integration method coupled with dual time-step sub-iteration. The Spalart-Allmaras one-equation model is employed for the turbulence effect. The computed results of the oscillating airfoil having a thin wake showed that the lift curve slope is increased and the magnitude of hysteresis loop is reduced by the interference effects. Since the vortex around the airfoil is generated and convected downstream faster than the free-air condition, the phase of lift, drag and pitching moment coefficients was shifted. The pressure on the test section wall shows harmonic terms having the oscillating frequency contained in the wail effect.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.424-424
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• 2000

The implementation of a insect-based flying microrobot has been previously proposed as using magnetic force. The flying principle of a butterfly is different from that of a airplane, which obtain lifting force above the wings by a air stream with low pressure. Butterflies obtain lifting force below the wings by flapping. They can fly when drag during the down stroke is greater that during the up stroke. The structure of flying microrobot must satisfy these condition. And that must be manufacture lightly and keep balance for rising to the air sufficiently. Moreover the efficiency of an electromagnet is high and the flux density is sustained uniformly and widely Nevertheless these condition is satisfied, the implementation of a flying microrobot is very difficult as the flying microrobot has to fly without guides or sensor. We propose differently a new model il] comparison with that other paper has suggested. This imitates the form of the Korean shield-shaped kite.