• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.6
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• pp.498-504
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• 2011

The flapping characteristics and advance ratios at torque equilibrium state of autorotation were investigated when the airspeed, shaft angle, and pitch angle were varied. To simulate the airspeed increase, the aerodynamic data analyzed by using the compressible Navier-Stokes solver and Pitt/Peters inflow theory were used. Transient Simulation Method(TSM) was used to catch the torque equilibrium states. The maximum flapping angles at torque equilibrium state were correlated to the airspeed, shaft angle, and pitch angle. By comparing flapping behavior to the variation of advance ratio, the phenomenon that the extension of reverse flow area of retreating blade affects the characteristics of autorotation was qualitatively considered.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.53-58
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• 2006

Along with the development of costal engineering, various type of breakwaters have been built. The main purpose of breakwaters are to provide harbour protection against waves, to stabilize beaches against erosion due to large wave action, and to provide for temporary wave protection for installation on or under water surface. This paper an application example of PIV system for analyzing the flow of Floating Breakwater with double barriers. We introduce an analysis method to predict the characteristics of flow around the neighboring fields of Floating Breakwater with double barriers in order to develop a high performance model. Flow visualization has conducted in circulating water channel by a high speed camera and etc. Flowing phenomenon according to velocity distribution and flow separation around the breakwater with double barriers were obtained by 2-D PIV system.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.43-54
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• 2004

A visualization study was carried out to investigate the effects of phase difference qualitatively by examining wake pattern on the phase difference of a dragonfly type wing model. The model was built with scaled-up, flapping wings composed of a paired wing with fore- and hind-wings in tandem that mimick the wing form of a dragonfly. The present study was conducted by using the smoke-wire technique and an electronic device below the tandem wings was mounted to find the exact wing position angles. Uncertainties in wing position angle are about $\pm$$1.0^{\cire}$ and instantaneous wing positional angle varies from $-16.5^{\cire}$ to $+22.8^{\cire}$. The tests were made at phase differences between the fore-wing and hind-wing at $0^{\cire}$, $90^{\cire}$, $180^{\cire}$ and $270^{\cire}$. The results show that Karman vortex structures were produced at phase differences of $90^{\cire}$, $180^{\cire}$ and $270^{\cire}$, but Karman vortex structures were not observed at the phase difference of $0^{\cire}$.