• International Journal of Aeronautical and Space Sciences
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• v.9 no.1
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• pp.121-128
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• 2008

This paper describes the modeling and autopilot design procedure of a Blended Wing-Body(BWB) UAV. The BWB UAV is a tailless design that integrates the wing and the fuselage. This configuration shows some aerodynamic advantages of lower wetted area to volume ratio and lower interference drag as compared to conventional type UAV. Also, BWB UAV may be increase payload capacity and flight range. However, despite of these benefits, this type of UAV presents several problems related to flying qualities, stability, and control. In this paper, the detailed modeling procedure of BWB UAV and stability analysis results using the linearized model at trim condition are represented. Finally, we designed the autopilot of BWB UAV based on a simple control allocation scheme and evaluated its performance through nonlinear simulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.5
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• pp.56-64
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• 2020

A wind tunnel test of 29.7% scaled model of NASA Common Research Model was performed in small low speed wind tunnel. The wind tunnel model was fabricated in Aluminium in consultation with NASA Langley Research Center and AIAA Drag Prediction Workshop committee members. The static aerodynamic forces and moments were measured at a relatively low Reynolds number of 0.3 × 10⁶ due to tunnel capability limitations. Pitching moment of three types of model support(Fin sting, Blade sting and Belly sting) were compared. The pitching moment for corrected Belly sting and Fin sting were similar. The result of pitching moment for Blade sting was very small.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.118-126
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• 2004

The propulsive characteristics of oscillating flat plates are investigated using a discrete vortex method. The plates and their wakes are represented by discrete point vortices. To analyze the closely coupled aerodynamic interference between the plates, a vortex core model and a vortex core addition scheme are combined. A calculated wake shape for a flat plate in heaving oscillation is compared with flow visualization. The effect of wake shapes on the propulsive characteristics of the plates in pitching oscillation is investigated. The propulsive characteristics of oscillating plates with three cases (1. one is stationary and another is oscillating, 2. both oscillating in phase, 3. both oscillating out of phase) are calculated. The plates oscillating out of phase showed the largest thrust force among the three cases.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.3
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• pp.187-194
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• 2020

In this study, computational analyses are carried out to investigate the interference flows and the aerodynamic characteristics of a hit-to-kill intercepter due to lateral jets at medium altitude. In addition, the analyses are performed for air and multi-species gas used in the side jet. The results indicate that the position of the barrel shock are shifted upstream and the structure of the shock wave are changed for the multi-species jet when compared to the air jet. As a result, the high pressure region with multi-species jet moves forward and the pitching moment is higher under the same flow condition. Moreover, the inclusion of high temperature effects makes drastic changes in pressure distribution. The jet width is much bigger, and the jet diffuses over wider range in medium altitude than in low altitude, because of the low density of the freestream.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.2
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• pp.89-97
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• 2020

In this study, a numerical analysis was performed on 26 inch single and coaxial propeller using the ANSYS Fluent 19.0 Solver to analyse the effect of the distance between coaxial propellers as one of the design parameter. The Moving Reference Frame (MRF) method was used for single propeller, while the sliding mesh method was used for a coaxial propeller to analyse the flow field varying with azimuth angle. The thrust and power are decreased as the upper and lower propeller approaching each other. As H/D is increased, interference between the propellers is decreased. According to the flow field variable contour of the coaxial propeller, it appears that the change in aerodynamic performance is due to the loading effect and the tip vortex wake effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.562-570
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• 2009

An Experimental study was conducted on the flow characteristics and interference heating caused by a two-dimensional object protruding from a flat plate using a blow-down type of hypersonic wind tunnel. Inflow condition was a free-stream Mach number of 7.0 and a unit Reynolds number of $2.0{\times}10^6/m$. Experimental conditions were varied with three heights of protuberance for two flat plate models which have different lengths. Experimental data were obtained from Schlieren visualization images and heat flux measurements. Also, this paper suggests hypersonic experimental techniques such as boundary-layer detection method in detail. A Large separation region was observed in front of the protuberance and that region was very sensitive to the height of protuberance and the length of the flat plate. For only the highest protuberance, a severe jump of heat flux was observed at the top station among the measuring points. Measured heat flux is large when the height of protuberance is large and the length of flat plate is long.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.114-122
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• 2022

This paper explores three-dimensional unsteady computational fluid dynamic (CFD) analyses with an overset grid technique to analyse the wake effect created by a rotating propeller on a hand-launched unmanned aerial vehicle (UAV). Additionally, the influence of actual aileron deflection on the equilibrium condition of the rolling moment is examined in various hand-launched take-off conditions. The results of this study demonstrate the importance of initial aileron deflection in increasing the initial rolling stability during the hand-launched take-off process. Furthermore, an aerodynamic database is constructed to rapidly predict the aileron set values required for different take-off speeds and angle-of-attacks.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.319-332
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• 2015

The pressure wave formed by the piston effects of the train proceeds within the tunnel when a train enters the tunnel with a high speed. Depending on the condition of tunnel exit, the compression waves reflect at a open end, change to the expansion waves, transfer to tunnel entrance back. Due to interference in the pressure waves and running train, passengers experience severe pressure fluctuations. And these pressure waves result in energy loss, noise, vibration, as well as in the passengers' ears. In this study, we performed comparison between numerical analysis and field experiments about the characteristics of the pressure waves transport in tunnel that appears when the train enter a tunnel and the variation of pressure penetrating into the train staterooms according to blockage ratio of train. In addition, a comparative study was carried out with the ThermoTun program to examine the applicability of the compressible 1-D model(based on the Method of Characteristics). Furthermore examination for the adequacy of the governing equations analysis based on compressible 1-D numerical model by Baron was examined.