• Wind and Structures
• /
• v.4 no.2
• /
• pp.163-176
• /
• 2001

Two 12 m high tubular steel lighting columns have been instrumented to determine the wind-induced fatigue loading experienced by such columns. Each column supported a single luminaire mounted on a 0.5 m long bracket. One column was planted in soil, and the other bolted through a welded baseplate to a substantial concrete base. The columns were strain gauged just above the shoulder weld which connected the main shaft to the larger base tube. Forced vibration tests were undertaken to determine the natural frequencies and damping of the columns. Extensive recordings were made of response to winds with speeds from 4 m/s to 17 m/s. Selected records were analysed to obtain stress cycle counts and fatigue lives. Mean drag coefficients were also derived from the strain data to investigate experimentally the effect of Reynolds Number.

• Journal of Aerospace System Engineering
• /
• v.2 no.2
• /
• pp.1-7
• /
• 2008

Recently the wind energy has been alternatively used as a renewable energy resource instead of the mostly used fossil fuel due to its lack and environmental issues. This work is to propose a structural design and analysis procedure for development of the low noise 100W class small wind turbine system which will be applicable to relatively low speed region like Korea and for the domestic use. Structural analysis including load cases, stress, deformation, buckling, vibration and fatigue life was performed using the Finite Element Method, the load spectrum analysis and the Miner rule. In order to evaluate the designed structure, the structural test was carried out and its test results were compared with the estimated results. In addition, the blade should be safe from the impact damage due to FOD(Foreign Object Damage) including the bird strike. In order to analize the bird strike penomena on the blade, MSC. Dytran was used, and the applied method Arbitrary Lagrangian-Eulerian was evalud by comparison with the previous study results.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.11 no.6
• /
• pp.115-122
• /
• 2012

The purpose of this study is to optimize the design of the jack-up platform for 5MW offshore wind turbine system. Considering all the environmental loads such as currents, waves, winds and so on, the members of structures have been designed and optimized based on the AISC and API-RP-2A to be within the allowable stress even in the most critical and severe condition. In addition to the above strength check of structural members, the joint punching shear check and the hydrostatic collapse check are also performed where they are required for the design. The design life of the jack-up platform is 50 years for the static strength check and the fatigue design life is 100 years including to the DFF(Design Fatigue Factor) of 2.0 to have enough stability and workability for the design optimization.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.304-307
• /
• 2006

Recently, as the global warming by fossil fuels and the steep rise of the oil price become social issues, the interest for renewable energy producing system is increasing rapidly. Among these, the wind turbine is most highlighted because of its economic competitiveness. The tower is one of the main components of wind turbine, which occupying about 20% of overall turbine costs. The tower access door located to base part of the tower, is used to enter the tower. This is the main structural weak points because of door hole, weldment, etc. And so are the weldments between the cans and the flanges. In this study, for the top flange part of the tower, by FEM using ANSYS, we retrieved the maximum von Mises stress on that and carried out fatigue analysis using stresses at such weak points.

• Wind and Structures
• /
• v.5 no.5
• /
• pp.463-478
• /
• 2002

Lighting and traffic signal columns are mainly stressed by excitation due to natural, gusty wind. Such columns typically have a door opening about 60 cm above ground level for the connection of the buried cable with the column's electric system. When the columns around this notch are inadequately designed, vibrations due to gusty winds will produce considerable stress amplitudes in this area, which lead to fatigue cracks. To give a realistic basis for a reliable and economic design of lighting and traffic signal columns, a number of experimental and theoretical investigations have been made. The proposed design concept allows the life of such columns to be assessed with a satisfactory degree of accuracy.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.22 no.1
• /
• pp.34-46
• /
• 2010

We observed tidal currents throughout all four seasons in 2007 at a single station, located 1.6km off Haeundae Beach and compared these current data with wind data. The direction of seasonal wind represented a similarity between the winds at sea and on land but the speed of wind at sea was almost three times stronger than the wind on land. In addition, the wind at sea turned out to considerably affect on tidal currents, particularly from late summer to autumn. On the other hand, the thickness of Ekman Layer, indicating a limitation of wind influence, was estimated to be 31.8 m on average, suggesting that the entire water column is under the influence of wind. Therefore, we are required to consider the wind stress into the analysis of tidal currents for the prevention of the loss of sand from Haeundae Beach.

• 한국해양학회지
• /
• v.29 no.4
• /
• pp.325-337
• /
• 1994

The distributions of heat and momentum fluxes on the surface over the oceans around the Korean Peninsula are obtained based on the surface-layer flux model of Kim and Kang (1994), and their seasonal variations are examined in the present study. the input data of the model is the oceanatmosphere data with a grid interval of 2$^{\circ}$ in longitude and latitude. The atmosphere data, which are the pressure, temperature, and specific humidity on the 1000 mb level for 3 year period of 1985∼1987, are obtained from the European center for Medium Range Forecast. The sea surface temperature (SST) is obtained from National Meteorological Center (NMC). The solar insolation and longwave radiation on the ocean surface are obtained, respectively, from the NASA satellite data and based on an emprical formula. It is shown from the net heat flux that the oceans near Korea lose heat to the atmosphere in January and October with the rates of 200∼ 400 Wm/SUP -2/ and 100 Wm/SUP -2/, respectively. But the oceans are heated by the atmosphere in April and July with about the same rate of 100 Wm/SUP -2/. The annualmean net heat flux is negative over the entire domain except the northern part of the Yellow Sea. The largest annual-mean cooling rate of about 120 Wm/SUP -2/ is appeared off the southwest of Japan. In the East Sea, the annual-mean cooling rate is 60∼90 Wm/SUP -2/ in the southern and northern parts and about 30 Wm/SUP -2/ in the middle part. The magnitude of wind stress in january is 3∼ 5 times bigger than those of the other months. As a result, the spatial pattern of annual-mean wind stress is similar to that of January. It is also shown that the annual-mean wind stress curl is negative. in the East China Sea and the South Sea,but it is positive in the northern part of the Yellow Sea.In the East sea,the stress curl is positive in the southeast and northern parts and negative in the northwestern part.

• Ocean and Polar Research
• /
• v.34 no.4
• /
• pp.395-401
• /
• 2012

Ten-year AVHRR sea surface temperature data obtained in the Yellow Sea are put into EOF analyses. Temperature variation is predominated by the first mode which is associated with the seasonal fluctuation of temperature with annual range decreasing with the bottom depth. Since such a strong annual signal may mask the upwind or downwind flows occurring intermittently during the winter, only the data obtained during this season are put into EOF analyses. Every winter shows similar results. The first mode, explaining more than 90% of total variance, appears to be a part of the seasonal variation of temperature mentioned above. In the second mode, the time coefficient is well correlated with northerly winds to which the responses of the trough and shallow coastal areas are opposite to each other. A simple theoretical consideration suggests the following physical explanation: The northerly wind stress anomaly creates an upwind (downwind) flow over the trough (coastal) areas, which then induces a temperature increase (decrease) by advection of heat, and vice versa for the southerly wind stress anomaly. Hence, this paper provides further evidence of the intermittent upwind or downwind flows occurring in the Yellow Sea every winter.

• The KSFM Journal of Fluid Machinery
• /
• v.14 no.2
• /
• pp.52-58
• /
• 2011

In this study, the design and verification of 6 kW class lift-type vertical-axis wind turbine (VAWT) has been conducted using advanced CAE technique based on computational fluid dynamics (CFD), finite element method (FEM), and computational structural dynamics (CSD). Designed aerodynamic performance of the VAWT model is tested using unsteady CFD method. Designed structural safety is also tested through the evaluation of maximum induced stress level and resonance characteristics using FEM and CSD methods. It is importantly shown that the effect of master eccentricity due to rotational inertia needs to be carefully considered to additionally investigate dynamic stress and deformation level of the designed VAWT system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.04a
• /
• pp.663-670
• /
• 2011

In this study, the design and verification of 6kW class lift-type vertical-axis wind turbine (VAWT) has been conducted using advanced CAE technique based on computational fluid dynamics (CFD), finite element method (FEM), and computational structural dynamics (CSD). Designed aerodynamic performance of the VAWT model is tested using unsteady CFD method. Designed structural safety is also tested through the evaluation of maximum induced stress level and resonance characteristics using FEM and CSD methods. It is importantly shown that the effect of master eccentricity due to rotational inertia needs to be carefully considered to additionally investigate dynamic stress and deformation level of the designed VAWT system.