• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.9
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• pp.843-852
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• 2000

The flow characteristics and the heat transfer rate on a surface by interaction of a pair of vortices were studied experimentally. The test facility consisted of a boundary-layer wind tunnel with a vortex introduced into the flow by half-delta winglet protruding from the surface. In order to control the strength of the longitudinal vortices, the angles of attack of the vortex generators were varied from $\pm20\;degree\;to\;\pm45$ degree, but spacings between the vortex generators were fixed to 4 cm. The 3-dimensional mean velocity measurements were made using a five-hole pressure probe. Heat transfer measurements were made using the thermochromatic liquid to provide the local distribution of the heat transfer coefficient. By using the method mentioned above, the following conclusions were obtained from the present experiment. The boundary layer was thinned in the regions where the secondary flow was directed toward the wall and thickened where it was directed away from the wall. The peak augmentation of the local heat transfer coefficient occurred in the downwash region near the point of minimum boundary-layer thickness.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.170-175
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• 2005

The focus of this paper is to observe the aerodynamic and vibration characteristics of the NACA0012 blade(AR=16.6) fixed on the lower surface of the wind tunnel, by changing air speed and the blade's angle of attack. After fixing a slit-typed vortex generator on the front of the blade, it could be observed that the vibrational characteristics caused by interactions between vortex and blade through the 5-hole pilot tubes. And, also, two different blades in stiffness had been prepared for observing those characteristics above in this experiment. The results were compared with the given stiffness of blade, as well. According to the results, it is clear to recognize that the vibration spectrum increases while air speed and angle of attack increase, and, also, less stiffness means bigger vibration spectrum.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.10
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• pp.962-968
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• 2008

An experimental study of the aerodynamic characteristics of a stealth configuration, the test techniques developed for the testing in the Low Speed Wind Tunnel of Agency for Defense Development(ADD-LSWT), and the lessons learned have been presented. The main objectives of this test are to determine the aerodynamic characteristics of a stealth configuration and to measure the flow field characteristics with a 5-hole pressure probe. The test results are discussed and the effect of the leading edge shape on the aerodynamic characteristics is also given.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.45-55
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• 2012

The road luminaires have been treated as subsidiary electric apparatuses in the road although they are indispensable facilities which people use the road safely. Because of this misunderstanding, there are not many researches on luminaire supports against the wind loads. Therefore, a typhoon has overturned or damaged many luminaire supports without having sufficient structural safeties. The purpose of this study is to review the current design criteria and to suggest the improvement of design methods based on the structural safety and compatible with the site conditions of luminaire supports. The stress concentration around the inspection hole, which causes the collapse of luminaire supports, is analyzed and stress reduction method is suggested with the improved design methods.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.3
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• pp.19-24
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• 2001

The Pilot-Tube is the device that measures velocity and altitude of high speed vehicle. Accurate measurements of speed and altitude are essential to the safe and efficient operation of aircraft. For the purpose of determining optimal design parameters of Pilot-Tube such as nose inlet configuration, nose shape, static hole configuration, and static hole location, subsonic flow field was calculated numerically and analyzed. A Pilot-Tube was manufactured based on numerical flow field analysis, and pressure and air velocity was measured experimentally in the wind tunnel. As a result manufacturing and design technologies of the Pilot-Tube were acquired to make flight-device.

• Journal of Bio-Environment Control
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• v.5 no.2
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• pp.187-193
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• 1996

This experiment was conducted to investigate the influence of temperature variation by the different ventilation methods on the growth and quality of oriental melon in greenhouse of tunnel type 1. The dropping effect in temperature by ventilation types was best at type 3 and those of type 2, type 1 were in order. 2. The temperature distribution in type 3 was uniformed as air- inflow and air- outflow by wind ventilation were easier than others. Whereas the temperature of type 1 having lateral ventilation hole and type 2 having the zenith ventilation tube and lateral ventilation hole was ascended, because small ventilation area of ventilation tube and hole could not make the gravity and wind ventilation successfully. 3. When compared with air amount of three types ventilated by the temperature difference of outside and inside of tunnel type house, that of type 3 was more than those of type 1 and type 2. 4. Type 3 was better than type 2 and type 1 in lear numbers, leaf area, fruit weight, flesh thickness, malformed fruit rate, and marketable fruit rate. 5. Marketable fruit rate of all treatment at each harvesting stages was rised, as goes to the latter periods.

• Food Science and Preservation
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• v.8 no.4
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• pp.356-361
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• 2001

This study was conducted to improve the storability of onion bulbs by assembly simple house storage and the reduce the rotteness caused by field open storage. Allium cepa cv. Changnyungdeago, late strain was used for the test at the storage condition of natural ventilation of levels 2, forced ventilation of levels 2, field open storage and 75mm, 100mm, and 125mm ventilating holes. Mean tamperature and relative humidity were not significantly different by ventilation conditions. Mean temperature was lower in forced ventilation than that of in natural ventilation and non-ventilation, and relative humidity was a little higher in ventilation treatment than those of the others. Weight loss of onion bulbs were 2.5%, 2.9%, 3%, 4.3% in field open storage, non ventilation, natural ventilation of levels 2 and forced ventilation of levels 2 respectively. Rotting rate in natural ventilation of levels 2 and farced ventilation of levels 2 were 27.7% and 25.4% respectively but 34.6% and 37.8% in non ventilation and field open storage. Therefore, the treatment of ventilation reduced the rotteness of storage onion bulbs. The smaller the size of a ventilating hole, the lower mean temperature was maintained. The relative humidity was some high in July, but didn’t showed significantly difference in August and September. With small size of a ventilating hole, the strong wind velocity was obtained, and wind velocity by position was weaker in the middle part than both ends. Rutting rates in 75㎜, 100㎜, and 125㎜ ventilating holes were 17.9%, 15.3% and 14.1% respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.337-342
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• 2016

A spudcan is mounted on the lower leg of the jack-up rig, a device for preventing a rollover of a structure and to support the structure in a stable sea floor. At the time of inserting the surface of the spud can to penetrate when the sand layer is stable and smoothly pulled to the clay layer, and at that time of recovery when uploading the spud can is equipped with a water injection device. In this study, it is significant to optimize the shape of pipelines holes for water injection device and it was set in two kinds of shape, the oval and round. Interpretation of the subject into the site of Gulf of Mexico offshore Wind Turbine Installation Vessels (WTIV) was chosen as a target platform. Using the ANSYS Workbench commercial programs, optimal design was conducted. The results of this study can be applied to the hole-shaped design of various marine structures.

• Journal of Astronomy and Space Sciences
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• v.18 no.1
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• pp.1-6
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• 2001

In this paper we investigate the properties of advection-dominated accretion flows (ADAFs) in case that outflows carry away infalling matter with its angular momentum and energy. Positive Bernoulli number in ADAFs allow a fraction of the gas to be expelled in a form of outflows. The ADAFs are also unstable to convection. We present self-similar solutions for advection-dominated accretion flows in the presence of outflows from the accretion flows(ADIOS). The axisymmetric flow is treated in variables integrated over polar sections and the effects of outflows on the accretion flow are parameterized for possible configurations compatible with the one dimensional self-similar ADAF solution. We explicitly derive self-similar solutions of ADAFs in the presence of outflows and show that the strong outflows in the accretion flows result in a flatter density profile, which is similar to that of the convection-dominated accretion flows(CDAFs) in which convection transports the angular momentum inward and the energy outward. There two different versions of the ADAF model should show similar behaviors in X-ray spectrum to some extent. Even though the two models may show similar behaviors, they should be distinguishable due to different physical properties. We suggest that for a central object of which mass is known these two different accretion flow should have different X-ray flux value due to deficient matter in the wind model.

• Journal of the Korea Safety Management & Science
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• v.8 no.6
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• pp.29-39
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• 2006

The effect of parameters on the consequence of the flash fire accident by the release of heavy gas(in this study, xylene vapor) was analyzed. Simulation results showed that the distance with the lower flammable limit($X_{LFL}$) was increased with the increase of the release hole diameter. For the case of the elevated release, $X_{LFL}$ was increased with the increase of the wind speed and the release height, but $X_{LFL}$ was not affected by the wind speed for the release on the ground level. Therefore, the accident in the elevated release was more dangerous than the release on the ground level. In this condition, the release height had more effect on $X_{LFL}$ at the night time than the daytime and in the urban area than the rural area.