• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.91-96
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• 1998

The broadband noise generated aerodynamically from a two-bladed axial flow fan has been measured and compared to the result of a self-noise prediction method. The prediction scheme is based on the experimental data set acquired from a series of aerodynamic and acoustic tests of two and three-dimensional airfoil blade sections. For low blade loading case the comparison showed a reasonably good agreement, but as the loading becomes larger the empirical formula overpredict the sound pressure level at high frequency range. This is probably due to the use of stationary wing data for the prediction of rotating blade case, which will be quite different in their vortex strength at the blade tip.

• 한국항공우주학회지
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• 제32권8호
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• pp.37-46
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• 2004

지면효과의 여러 현상을 Navier-Stokes 방정식을 이용하여 해석하고 공기역학적인 관점에서 그 결과를 분석하였다. 2차원 지면효과에 대해서는 이미지 와류에 의한 약형 표면의 압력변화, 두께의 영향, 지면효과의 비점성 유동 현상 등을 확인하였으며, 3차원 지면효과로 익단와류 강도의 증가현상과 유효스팬 증가, 익단와류의 바깥 흐름현상 등을 확인하였다. 또한, 재래식 익형인 NACA 6409와 러시아의 WIG기 전용익형인 DHMTU 8-30에 대해서 Irodov의 조건식을 사용하여 새로 정안정성을 해석하였다. 해석결과, DHMTU 8-30 익형의 세로 정안정성이 NACA 6409 익형보다 훨씬 우수한 것으로 나타났다. 그러므로 DHMTU 8-30을 WIG기에 사용할 경우 NACA 6409에 비해 꼬리날개 부피비를 현저히 줄일 수 있음을 확인하였다.

• 한국전산유체공학회지
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• 제18권3호
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• pp.8-13
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• 2013

Drag reduction of a running vehicle is very important issue for the energy savings and emission reduction of its power train. Especially for a solar powered electric vehicle, the drag reduction and weight lightening are two serious problems to be solved to extend its driving distance under the given energy condition. In this study, the ground effect of an airfoil shaped road vehicle was studied for an optimum body design of an ultra-light solar powered electric vehicle. Clark-Y airfoil type was adopted to the body shape of the model vehicle to reduce aerodynamic drag. From the study, it was found that the drag of the model vehicle was reduced as the height(h) between ground and the lower surface of the model vehicle was decreased. It is due to the reduction of the down-wash decreasing the induced drag of the vehicle. The lift was also decreased as the height decreased. It is due to the turbulent boundary layer developed beneath the vehicle body. The drag is classified into two types; the form and friction drag. The fraction of form drag to friction one is 76 to 24 on the model vehicle. As the height(h) of the model vehicle from the ground surface increases the form drag also increases but the friction drag is in reverse.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권1호
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• pp.55-65
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• 2017

Underwater torpedo has control fin with very low aspect ratio due to launching from limited size of cylindrical torpedo tube. If the aspect ratio of control fin of underwater vehicle is very low three-dimensional flow around control fin largely reduces control forces. In this study, the end plate was applied to reduce the three-dimensional flow effects of partially movable control fin of underwater vehicle. Through numerical simulations the flow field around control fin was examined with and without end plate for different flap angles. The pressure, vorticity, lift and torque on the control fin were analyzed and compared to experiments. The comparison have shown a reasonable agreement between numerical and experimental results and the effect of end plate on a low aspect ratio control fin. When the end plate was attached to the movable control fin, the lift increased and the actuator shaft torque did not significantly change. As this means less consumption of the actuator shaft torque compared to the control fin that has the same control force, the inner actuator capacity can be reduced and energy consumption can be saved. Considering this, it is expected to be effectively applied to the control fin design of underwater vehicles such as torpedoes.