• Journal of computational fluids engineering
• /
• v.20 no.2
• /
• pp.61-66
• /
• 2015

In this study, an aero-acoustic analysis around pantograph of a high speed train is performed. Computational technique and grid system is validated with wind tunnel test result and unsteady acoustic pressure data are used for analyzing noise level of each part of pantograph. FLUENT is used for flow analysis and LES(Large Eddy Simulation) is applied for analyzing turbulent flow. For acoustic analysis, Ffowcs Williams-Hawkings(FW-H) acoustics model is used and it bring the aero-acoustic characteristic of pantograph. As the result, contact strip, knee, substructure of pantograph is confirmed as a main source of aero-acoustic noise and it is dealt in various frequencies. The result is expected to help building improved grid system.

• Proceedings of the KIEE Conference
• /
• 2005.07a
• /
• pp.521-523
• /
• 2005

A Jumper wire is currently used to connect each fixed power line on both sides of dead end tower for overhead transmission line, but in case of a jumper wire swing under circumstances of typhoon, etc. and the air clearance is deficient then a flashover fault may Happen. Now the angle tower has the jumper support string to prevent a swing of jumper wire and to secure the air clearance between jumper wire and tower main body, but the flashover fault by swing of jumper wire was happened yl times across all over the country, because of the typhoon 'Rusa' in year 2002 and 'Maemi' in year 2003. This paper presents the design and development of 'Counter Weight' which enables to keep the swing angle of jumper wire under 40 degree in design condition to prevent a flashover fault by swing of jumper wire by a high wind pressure load in case of typhoon and have completed a mechanical and electrical characteristic test.

• 유체기계공업학회:학술대회논문집
• /
• 2001.11a
• /
• pp.11-16
• /
• 2001

It is not easy to apply a small-sized centrifugal fan to the duct used for the thermal management of home electronic appliances due to complex design parameters of its blades and scroll. The main objective of this study was to develop the systematic process to design an optimal centrifugal fan based on the 3-dimensional configuration of blades obtained from the conceptual design program self-developed with the given design constraints such as the flow rate, the total pressure loss, the size of fan, and the number of rotation. The design process to find an optimal centrifugal fan for refrigerator was technologically linked in many ways. The complex grid generation system of the fan model included scroll was adopted for the numerical simulation. The FVM CFD code, FLUENT, was used to investigate the three dimensional flow pattern at the coordinate system of rotating frame and to check the optimal performance of the fan. By using this design process, a selected centrifugal fan was designed, numerically simulated, manufactured and experimentally tested in the wind tunnel. The performance curve of fan manufactured by NC process was compared with numerically obtained characteristic curve. The developed design method was proved into being excellent because these two curves were well matched.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.6
• /
• pp.14-22
• /
• 2008

This study is aimed at suggesting a linear-type diffuser which is excellent in terms of range and elegance like existing diffusers in which amount and direction of wind can be freely controled, out of linear-type diffusers with the highest possibility to be adopted for living space of apartments whose height between floors is not so high and utilizing the linear-type diffuser in design. For the purpose, I examined necessary flow and noise properties of linear-type diffusers. Besides, I evaluated its ventilation capacity for persons in there by applying this in the actual living space. I evaluated features and air blast and found that in time of horizontal and vertical effusion, its T/L ratio is 1-1.5, similar to existing cardioid-type linear diffusers, while in time of slope effusion, it is similar to horizontal effusion in terms of range and it has medium figure in terms of pressure drop and effusion speed, indicating it can provide safe and pleasant indoor environment for persons in there in terms of ventilation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.3
• /
• pp.658-663
• /
• 2008

In this study, we estimated the influence of electrical pole by FEM(Finite Element Method) and developed protective system by designing and interpreting protective system for electrical pole and overhead optical communication line when abnormal strength worked on messenger wire. Protective system did not shed messenger wire under wind pressure and discontent load but did assign a part to preventing rupture of electrical pole and disconnection of optical communication line through automatically shed messenger wire over fixed strength. Structure of protective system analysis by FEM and prove property by measuring tensile strength for practical product.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.1
• /
• pp.41-52
• /
• 2021

During atmospheric ascent of a launch vehicle, airborne acoustic loads act on the vehicle and its effect becomes pronounced at transonic speed. In the present study, acoustic loads acting on a hammerhead launch vehicle at a transonic speed have been analyzed using ��-ω SST based IDDES and the results including mean Cp, Cprms, and PSD are compared to available wind-tunnel test data. Mesh dependency of IDDES results has been investigated and it has been concluded that with an appropriate turbulence scale-resolving computational mesh, the characteristic flow features around a transonic hammerhead launch vehicle such as separated shear flow at fairing shoulder and its reattachment on rear body as well as large pressure fluctuation in the region of separated flow behind the boat-tail can be predicted with reasonable accuracy for engineering purposes.

• Proceedings of KOSOMES biannual meeting
• /
• 2008.05a
• /
• pp.185-189
• /
• 2008

This study was conducted to find out the effects of relationship between ocean conditions and snowfall when cold and dry continental air mass passes through the West Sea of Korea. Route of continental high atmospheric pressure can cause effect on snowfall at the west regions (Inchoen, Gunsan, Mokpo) of the Korean Peninsula. The continental high atmospheric pressure extend from the southern China to western coastal region of the Korean Peninsula during the December, and it extend from the north side of China through Bohai Sea and Yodong Peninsula to central area of the Korean Peninsula during the February. Therefore, more snowfall recorded in Incheon is higher during Feb. than Dec.. whereas Gunsan and Mokpo is the opposite. The heavy snowfall at the western coastal region of Korea was caused by loss of the heat from the ocean to air when it's higher than $100W/m^2$. the heavy snowfall was also observed when the arrangement of continental high atmospheric pressure and low pressure was high at the West and low at the East, which formed a front in West and when the wind blow from the North or North West at the speed of $4\sim8m/sec$. There were not much relation between salinity in the western sea and snowfall in the western coastal region of Korea.

• International Journal of Highway Engineering
• /
• v.13 no.4
• /
• pp.159-166
• /
• 2011

Green house gas emissions are increasing as development of the industrial economy of the international community. Many countries in the world are endeavoring to reduce green house gas emissions under severe climate change. In order to protect grobal warming, government is trying to reduce green gas emissions under "Low Carbon Green Growth Policy" and investing climiate-firendly industries such as renewable energy harvesting. Renewable energy has been rapidly developing as a result of investment for development technology of using natural energy such as solar, wind, tidal, etc. There are lots of waste energy in the road space. However, nobody is not interested in waste energy from the road space. This paper present a fundamentally experimental study of energy harvesting technique to use waste energy in the road. The waste energy in the road is covered a pressure and impact of vehicles on the road, the radiant heat from asphalt pavement, road noise and vibration etc. In this study, an energy harvesting device using piezoelectric element is proposed and various tests are conducted to investigate a characteristic of this device as function of impact loading based on piezoelectric effect behavior. This paper shows the energy harvesting results of the device using domestic piezoelectirc element as a function of impact load size and pavement types.