• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.3 no.1
• /
• pp.1-13
• /
• 1991

A wave prediction model of DP type with shallow water effects is composed. An jntercomparison study of the deep water wave models has been made to clarify the capacity of this model which has source functions by Incur and propagation scheme by Gadd. It is shown that the growth rate of wave energy is rapid and. for asymmetrical wind fields. this model behaves well. In spite of various response pattern for the wind fields the energy distribution gives reasonable agreements with those of other models.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.486-493
• /
• 2010

Recently, it has been a worldwide issue to develop offshore wind farm based on the past technical experiences of onshore wind turbine installation. In Korea, the government has the wind-energy to be a new-sustainable field of development to bring green-growth in near future and put political and fiscal efforts to support the academic and industrial technical development. Especially, there are much advancement for the fields of turbine, blade, bearing, grid connection, ETC. Correspondingly, technical needs do exist for the offshore foundation installation techniques in geotechnical point of view. Within few years, 2~5MW offshore wind turbines will be constructed at about 30m water depth and it is known that monopiles of D=4~6m are suitable types of foundation. In order to construct offshore wind-turbine foundation, technical developments for drilling machine, design manual, monitoring&maintenance technique are required. This paper presents technical issues with related to offshore wind farm and large diameter monopile in the point of renewable energy development.

• Bulletin of the Korean Space Science Society
• /
• 2003.10a
• /
• pp.34-34
• /
• 2003

To better understand how high-latitude electric fields influence thermospheric dynamics, we study winds in the high-latitude lower thermosphere using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model of the National Center for Atmospheric Research (NCAR/TIEGCM). In order to compare with Wind Imaging Interferometer (WINDII) observations the model is run for the conditions of 1992-1993 southern summer. The association of the model results with the interplanetary magnetic field (IMF) is also examined to determine the influences of the IMF-dependent ionospheric convection on the winds. The wind patterns show good agreement with the WINDII observations, although the model wind speeds are generally weaker than the observations. It is confirmed that the influences of high-latitude ionospheric convection on summertime thermospheric winds are seen down to 105 km. For negative and positive IMF By the difference winds, with respect to the wind during null IMF conditions, show significantly strong anticyclonic and cyclonic vortices, respectively, down to 105 km. For positive IMF Bz the difference winds are largely confined to the polar cap, while for negative IMF Bz they extend to subauroral latitudes. The IMF Bz-dependent diurnal wind component is strongly correlated with the corresponding component of ionospheric convection velocity down to 108 km and is largely rotational. The influence of IMF By on the lower thermospheric summertime zonal-mean zonal wind is substantial at high latitudes, with maximum wind speeds being 60 m/s at 130 km around 77 magnetic latitude.

• Wind and Structures
• /
• v.5 no.2_3_4
• /
• pp.329-336
• /
• 2002

The along-wind response of a surface-mounted elastic fence under the action of wind was investigated numerically. In the computations, two sets of equations, one for the simulation of the unsteady turbulent flow and the other for the calculation of the dynamic motion of the fence, were solved alternatively. The resulting time-series tip response of the fence as well as the flow fields were analyzed to examine the dynamic behaviors of the two. Results show that the flow is unsteady and is dominated by two frequencies: one relates to the shear layer vortices and the other one is subject to vortex shedding. The resulting unsteady wind load causes the fence to vibrate. The tip deflection of the fence is periodic and is symmetric to an equilibrium position, corresponding to the average load. Although the along-wind aerodynamic effect is not significant, the fluctuating quantities of the tip deflection, velocity and acceleration are enhanced as the fundamental frequency of the fence is near the vortex or shedding frequency of the flow due to the occurrence of resonance. In addition, when the fence is relatively soft, higher mode response can be excited, leading to significant increases of the variations of the tip velocity and acceleration.

• Wind and Structures
• /
• v.9 no.3
• /
• pp.231-243
• /
• 2006

An improvement to the spectral representation algorithm for the simulation of wind velocity fields on large scale structures is proposed in this paper. The method proposed by Deodatis (1996) serves as the basis of the improved algorithm. Firstly, an interpolation approximation is introduced to simplify the computation of the lower triangular matrix with the Cholesky decomposition of the cross-spectral density (CSD) matrix, since each element of the triangular matrix varies continuously with the wind spectra frequency. Fast Fourier Transform (FFT) technique is used to further enhance the efficiency of computation. Secondly, as an alternative spectral representation, the vectors of the triangular matrix in the Deodatis formula are replaced using an appropriate number of eigenvectors with the spectral decomposition of the CSD matrix. Lastly, a turbulent wind velocity field through a vertical plane on a long-span bridge (span-wise) is simulated to illustrate the proposed schemes. It is noted that the proposed schemes require less computer memory and are more efficiently simulated than that obtained using the existing traditional method. Furthermore, the reliability of the interpolation approximation in the simulation of wind velocity field is confirmed.

• 한국태양에너지학회:학술대회논문집
• /
• 2008.11a
• /
• pp.96-102
• /
• 2008

For centuries now, wind tunnels have been a key element in scientific research in a number of fields. Experimenting with racecars, airplanes, weather patterns, birds, and various other areas has been made much easier because of its development. In the racing field, for example, the information gathered from this testing can mean the difference between winning and losing a race. Weather simulations can also provide valuable information regarding building stability and safety. This has become very important when designing buildings today. Valuable information concerning bird flight has also been collected based on wind tunnel testing. Wind tunnels have a variety of important uses in the world today. Wind tunnel that used here is an open loop low speed wind tunnel. The fundamental principles of this tunnel is moving the air using exhaust fan In the rear side, and placing the cube in the external balance system which used to measure the working force. This experiment is using 50mm cube of finished wood. From this experiment we can get Drag Force (FD), The Reynolds Number (Re) and The Coefficient of Brae (CD).

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.10a
• /
• pp.274-277
• /
• 2008

To evaluate high-resolution wind resources for local and coastal area with complex terrain was attemped to combine the prognostic MM5 mesoscale model with CALMET diagnostic modeling this study. Firstly, MM5 was simulated for 1km resolution, nested fine domain, with FDDA using QuikSCAT seawinds data was employed to improve initial meteorological fields. Wind field and other meteorological variables from MM5 with all vertical levels used as initial guess field for CALMET. And 5 surface and 1 radio sonde observation data is performed objective analysis whole domain cells. Initial and boundary condition are given by 3 hourly RDAPS data of KMA in prognostic MM5 simulation. Geophysical data was used high-resolution terrain elevation and land cover(30 seconds) data from USGS with MM5 simulation. On the other hand SRTM 90m resolution and EGIS 30m landuse was adopted for CALMET diagnostic simulation. The simulation was performed on whole year for 2007. Vertical wind field a hour from CALMET and latest results of MM5 simulation was comparison with wind profiler(KEOP-2007 campaign) data at HAENAM site.

• Journal of Ocean Engineering and Technology
• /
• v.21 no.1 s.74
• /
• pp.1-6
• /
• 2007

While a typhoon is traveling, characteristics of its wind fields are continuously changing, producing severe changes in local water level and wave conditions, especially, when a typhoon comes into shallow water. However, there have not been many studies related to local typhoon effects, especially, considering real time changes of wind direction related to the coastal topography. In the study, the characteristics of the wind field by typhoon and topographical characteristics in shallow water are considered, as well as conditions of wave climate estimation. These are performed by the SWAN (Simulating waves nearshore) model, in order to estimate the growth of wave energy due to the wind field. It can be strongly suggested that the wave energy of theof an inner bay should be estimated when the direction of the bay entrance and the wind direction of the typhoon are identical. The result of the numerical calculations is in better agreement with the observed data than the result of the conventional estimation techniques.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.7
• /
• pp.915-926
• /
• 1998

Velocity fields of near turbulent was behind a porous wind fence were measured using the 2-frame PTV method in a circulating water channel. The fences used in this study had different geometric porosity(.epsilon.) of 0, 20, 40 and 65%. The fence was embedded in a thin laminar boundary layer, i.e., .delta./H ~ = 0.1. Reynolds number based on the fence height H and free stream velocity(U$\_$o/) was about 8,400. As a result, a recirculating flow region was formed behind the fence for the .epsilon.=0% and 20% wind fence. For the wind fences having porosity larger than .epsilon.=40%, it was difficult to see separation bubbles behind the fence. The .epsilon.=20% porous fence reveals the maximum velocity reduction, however, the turbulent intensity and Reynolds shear stress are much greater than those of .epsilon.=40% fence. Among the wind fence tested in this study, the porous wind fence of .epsilon.=40% porosity is the most effective for abating wind erosion.

• Journal of Environmental Science International
• /
• v.6 no.6
• /
• pp.613-628
• /
• 1997

Diurnal variations of air quality due to the characteristic features of local weather phenomena over Kunsan, Taegu, and Pohang are analyzed using various synoptic wand fields and the characteristics of local weather during the period of 1990 to 1992. The air pollutants analyzed are sulfur dioxide($SO2_$), nitrogen dioxide($NO_2$), and oxidants ($0_3$). The synoptic wind fields estimated at over the 850 hPa geopotential height are divided in terms of four wand directions and two wand speed categories for each season. The synoptic weather conditions are also classified Into two categories depending on the 850 hPa cloud amounts. The present study shows that the $SO_2$ concentration over Kunsan, and Taegu was maximum at the two or three hours after sunrise and second primary was three or flour hours after sunset. On the other hand, Its concentration over Kunsan was malnmum at 1900 LST or 2000 LST The $O_3$ concentration over the three cities shows Its mapdmum In the afternoon when the solar radiation is strong. The $NO_2$ concentration over Kansan shows in reverse proportion to the $O_3$ concentration over the Kunsan.