• Journal of computational fluids engineering
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• v.18 no.1
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• pp.28-35
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• 2013

Behavior of the side force generated at high angles of attack by two ogive-cylinder bodies of revolution with nose fineness ratio of 2.3 (B1) and 3.5 (B2) and the effect of a strip placed close the nose tip of each body (B1S and B2S) are analyzed through the wind tunnel test at ReD=200,000 and a=42~60 deg. The side force generated by B1 is increased by placing a strip. The side force generated by B2 is in the starboard direction and its magnitude is higher than that of the B1S. The effect of the strips with various dimensions placed on B2 is investigated. It is found that the 4-layer strip placed on the starboard reversed the direction of the side force into port direction. It is confirmed by numerical simulations that the strip promotes the flow separation and increases the average pressure on the side where it is placed and consequently produces the side force in the corresponding direction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2431-2442
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• 1994

In this paper the efficient space marching Viscous Shock Layer and Parabolized Navier-Stokes method have been applied to study the complex 3-D hypersonic equilibrium chemically reacting flowfilelds over sphere-cone($10^{\circ}$) vehicle at low angles of attack($0^{\circ}~5^{\circ}), Mach 20, and an altitude of 35km. The current bluntbody/afterbody space marching numerical method predicts the complex flowfields accurately and efficiently even on a small computer. The shock thickness from equilibrium air model is thinner than that from the perfect gas model. The windside wall heat-transfer rate, pressure and skin friction force were increased significantly when compared with those of leeside. The CA, CN, CM were increased almost linearly with the angle of attack in this region. The wall pressure, heat transfer, skin friction and axial force coeffient from equilibrium model were much higher than those from perfect gas model. The center of pressure moved forward with the increase of angle of attack.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.61-70
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• 2006

A Supersonic air intake model was designed for the high performance ramjet and dual-mode scramjet engine to operate at Mach 4 flight condition. The air intake was tested in the blowdown-type wind tunnel of Kyushu University to identify the internal flow characteristics corresponding to the flight parameters such as the back pressure, angle of attack and angle of yaw. Flow visualization was achieved by the Schlieren and oil flow visualization techniques. The intake performance was analyzed quantitatively based on the surface pressure and total Pressure measurements. The experimental results were compared with the computational fluid dynamics results. The present study exhibits the fundamental but rarely found experimental results of the high Mach number supersonic air intake.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.7
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• pp.105-112
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• 2002

An experimental study of the vortical flow characteristics around a yawed delta wing with the leading edge extension at high incidence angle is undertaken by upper surface pressure measurements. A special emphasis has been put on analyzing the basic physics of vortical flows, concerning the effects of incidence and sideslip angle on the aerodynamic characteristics of the wing, especially under high angle of attack. The experimental data has been dearly demonstrated the beneficial effect of the LEX vortex on the wing vortex. It leads to an essential stabilization of the wing vortex against its breakdown until at much higher incidence angle under small sideslip. An interesting flow feature is occurrence of the rolling moment reversal at a certain range of angle of attack and sideslip angle.

• Korean Journal of Applied Biomechanics
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• v.23 no.2
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• pp.99-108
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• 2013

The purpose of this study was to analyze the kinematic characteristics of javelin to compare the characteristics between world elite athletes and local male athletes. The subjects selected 9 athletes out of total 13 athletes recorded more than 65 m in the preliminary and main competition participated in the 93rd National Sports Festival held in 2012. Three-Dimensional motion analysis using a system of 4 video cameras(Sony HXR-MC2000) at a sampling frequency of 60 fields/s was performed for this study. The Kwon3D 3.1 was used to obtain the three dimensional coordinates about the top, grip, end of javelin. And the kinematic factors of javelin calculated using Matlab2009a program. The resultant speed of javelin that affects directly to the record of performance showed 26.08 m/s indicated lower speed of about 2-3 m/s than world elite athletes. The release point appeared to have been made at the high of $1.79{\pm}0.07$ m of 99.8% of the height of the athletes. In terms of release angle, it was indicated average $33.0{\pm}3.81^{\circ}$ lower release angle compared to the world elite athletes. The attitude angle(up & down tilt angle, X axis) related to javelin indicated average $38.5{\pm}4.96^{\circ}$, its related attack angle average $5.5{\pm}5.11^{\circ}$, and yaw angle(sideslip, side attack angle) average $15.7{\pm}8.48^{\circ}$.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.3
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• pp.266-273
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• 2011

This paper deals with missile autopilot design for agile turn phase in air-to-air engagement scenarios. To attain a fast response, angle-of-attack (AOA) is adopted for an autopilot command structure. Since a high operational AOA is generally required during the agile turn phase, dealing with the aerodynamic uncertainties can be a challenge for autopilot design. As a remedy, a new controller design method based on robust nonlinear control methodology such as time delay control is proposed in this paper. Nonlinear observer is also proposed to estimate the AOA in the presence of the model uncertainties. The performance of the proposed controller with variation of the aerodynamic coefficients is investigated through numerical simulations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.825-834
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• 2008

Nose chine shape optimization study has been performed to maximize the directional stability at high angle of attack supersonic flow. Various chine shapes are generated using super ellipse equation. By numerically investigating the directional stability characteristics of those shapes, the baseline configuration for the shape optimization has been selected using the three-dimensional Navier-Stokes equations. The configuration is represented by the NURBS curves which can adjust the surface geometry by the control points. The response surfaces are constructed to obtain optimum shape which has high directional stability characteristics and lift-to-drag ratio. From this study, an efficient configuration design and optimization process which utilizes the parameter-based configuration generation techniques and approximation method has been established, then 29% improvement of the directional stability by strong vortexes from chine nose is accomplished.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.111-114
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• 2007

Computational Fluid Dynamics (CFD) and the Finite Element Method (FEM) are used to perform aerodynamics analysis and structure analysis. For the fluid-structure interaction analysis, each technology should be considered as well. The process of aerodynamics-structure coupled analysis can be applied to various integrated analyses from many research fields. In this study, the aerodynamics-structure coupled analysis is performed for the missile at high angle of attack condition through the use of Computational Fluid Dynamics (CFD) and the Finite Element Method (FEM). For this purpose, the aerodynamics-structure coupled analyses procedure for the missile are established. The results of the integrated analysis are compared with rigid geometry of the missile and the effect of the deformation will be addressed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.35-40
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• 2005

Maneuverability of ships has been receiving a great deal of attention both concerning navigation safety and the prediction of ship maneuvering characteristics, to improve it. high-lift device could be applied to design of rudder at design stage. Now, we carried out the flow visualization and investigation of flow field around a flap rudder(trailing-edge flap). Flow visualization results of flap defection shown as the flow around a NACA0020 Flap Rudder will be conducted in a Circulating Water Channel. The purpose of this investigation will be to investigate the development of the separation region on the flap rudder with the variation of the angle of attack and determine the angle of attack at which the flow separates and reattaches.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1453-1460
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• 2003

The present study investigates the effects of rib arrangements and aspect ratios of a rectangular duct simulating the cooling passage of a gas turbine blade. Two different V-shaped rib configurations are tested with the aspect ratios (W/H) of 3 to 6.82. One is the continuous V-shaped rib configuration with $60^{\circ}$ attack angle, and the other is the discrete V-shaped rib configuration with $45^{\circ}$ attack angle. The square ribs with the pitch to height ratio of 10.0 are installed on the test section in a parallel arrangement for both rib configurations. Reynolds numbers based on the hydraulic diameter are changed from 10,000 to 30,000. A naphthalene sublimation method is used to measure local heat/mass transfer coefficients. For the continuous V-shaped rib configuration, two pairs of counter-rotating vortices are generated in a duct, and high transfer region is formed at the center of the ribbed walls of the duct. However, for the discrete V-shaped rib configuration with $45^{\circ}$ attack angle, complex secondary flow patterns are generated in the duct due to its geometric feature, and more uniform heat/mass transfer distributions are obtained for all tested cases