High-voltage transmission lines with an overall length of several hundreds kilometers have been constructed across the mountainous area or the coastal zone, and directional strength characteristics of the transmission lines are found remarkably due to a high rate of wind load. Since the wind load is critical for transmission lines, it is important to assess the design wind speed and wind load reasonably at construction sites.After the attack of typhoon 9119 at September, 1991, which caused the damage of some power transmission towers, we carried out the research programs of the local wind load on transmission towers (from FY1992 to FY1999) and the rational wind-resistant design for transmission towers (from FY1999 to FY2001) with Electric Power Companies. As a result of the research, we provided "Recommendations for Wind Loads on Transmission Towers - a draft " In this paper, we describe the basic concept of the "Recommendations - a draft".

View full abstract

For rationalization of wind resistant design of transmission towers, it is important to estimate the design wind speed considering directional wind characteristics and geography effects of construction sites. Therefore, we made directional basic wind speeds maps (mean wind speed of 10 minutes, return period of 150 years) based on the observed data at meteorological stations, Monte Carlo simulations using a typhoon model and horizontal wind speed distribution obtained by air flow simulations. In addition, to evaluate speed-up ratio k1 by topography, we prepare the computer simulation method which could be considered 3-dimensional topographic feature and the simplified k1 prediction method based on the numerical results of speed-up ratio regarding the 2-dimensional escarpments with each slope angle. Although the latter method is usually conservative due to ignore the 3-dimensional effects, it could be easily incorporated into design procedure. Then we showed the design wind speed evaluation method considering meteorological effects.

View full abstract

For wind resistant design considering the directional design wind speed and structural characteristics of transmission lines, the accurate wind load evaluation for every wind direction is needed. Namely it is important to consider the dynamic effects of the tower-conductor systems, such as scale and resonance effect, as well as the wind speed influenced by topography and the wind direction. For this purpose, we proposed sub-system wind loads such as wind forces on tower, overhead wires and tension force of overhead wires considering dynamic effects based on gust effect factor method. In addition, we also developed a combination method of sub-system wind loads, based on theoretical study, wind tunnel tests and observations of test lines. Then we enabled the load evaluation corresponding to actual conditions.In this paper, we describe the feature of wind load evaluation method and the comparison results between Sikoku test line observations and predictions.

View full abstract

The destruction accident of power transmission towers occurred by the strong wind by the typhoon No. 21 in October, 2002.Tokyo Electric Power Company performed cause investigation of the accident, making full use of the newest wind engineering technology. Consequently, it was shown clearly that the cause of the accident is not that wind load exceeded the design value.

View full abstract

In this paper, the previous studies and the state-of-art of the evaluations of wind environment in various engineering fields (Meteorological, Traffic, Civil Engineering, Building etc.) are reviewed. These researches are based on the activity of Research Committee on Evaluation of Wind Environment, is organized by the Japan Association for Wind Engineering. This group consisted of researchers from several universities and private companies. From these results, it is confirmed that there are some regulations, rules and consensuses in each field of wind engineering.

View full abstract

This paper describes the legal problem concerning a wind gust due to high-rise building form the viewpoint of the lawyer.

View full abstract

In order to discuss the criteria of regulation rules against strong winds in operation of railway vehicle, a statistical analysis was carried out on wind speed difference in a few or 10 minutes. When a 10-minute-mean wind speed was above 10m/s below 20m/s, the frequency distribution of the following 10-minute-mean wind speed was found to be similar to a Normal Distribution near 0m/s difference, but to an exponential function with high increase in wind speed. The statistical characteristics of wind speed difference will be helpful in calculation of the probability that a vehicle meets with the critical gust.

View full abstract

This study brings into focus the turbulent boundary layer flow over a two-dimensional hill, which has special characteristics near the hill with favorable or adverse pressure gradient and surface curvature effect. In this paper, Smagorinsky (SM), Dynamic Smagorinsky (DSM), Dynamic mixed l(DMM)models are tested by a priori comparisons with filtered direct numerical simulation(DNS)data., over a hill.. In addition, we carried out large eddy simulation (LES) of unsteady flows over a two-dimensional steep hill for the oncoming boundary-layer turbulence, with the above three tested models.

View full abstract

Airflows over steep complex terrain with characteristic length scales of the order of kilometers contain the flow impingement, separation and reattachment. In order to develop an accurate model of simulating the above-mentioned topographic effects, we have been examining the large-eddy simulation (LES) technique using a finite-difference method (FDM). These LES codes are referred to as the RIAM-COMPACT (Research Institute for Applied Mechanics, Kyushu University, Computational Prediction of Airflow over Complex Terrain). In this research, comparison of the CSU-RAMS (Colorado State University and Regional Atmospheric Modeling System) and the RIAM-COMPACT was performed for a steep Noma cape.

View full abstract

We study on the roughness boundary condition for numerical simulation of surface boundary layers. The results of calculated mean wind speed profiles using the power-law and logalithmic-law are compared. The logalithmic-law condition can simulate wind profiles which have equivalent vertical wind speed distributions conditioned by the roughness length.

View full abstract

Recently, inflow turbulence for LES has been studied. These studies are divided into two classes, statistical method and unsteady flow simulation. The inflow turbulence generated by statistical method, has been applied in the case of homogeneous turbulence usually, is difficult to be applied to inflow boundary condition smoothly. While, It is expected inflow turbulence generated by unsteady flow simulation to be applied smoothly. In this paper, we propose the new model of inflow turbulence used forced turbulence. In addition, we validate the model used forced turbulence from the view point of turbulence statistics.

View full abstract

This paper describes the measurement results of mirostructure of turbulence and eddy diffusion coefficient in a forest. We measured the three components of mean and fluctuating velocities of wind by means of the ultrasonic anemometers at the observation tower in the forest of Kanazawa university. The values of mixing length and eddy diffusion coefficient in January are found ten times larger then those in October,and they are affected by the density of the leaves at each season.The results infer that tree leaves reduce eddy scales by behaving as elastic obstacles.From power spectra of wind speed fluctuations,inertial subrange is identified in high frequency range.Spatial scales which reflect magunitude of spatial structure of average flow are in the range of 10m-100m,which tend to increase with mean velocity.

View full abstract

Recently,it becomes to be very important to estimate the CO2 amount that plants absorb concerning to the warming phenomenon .In this paper,we carry out LES analysis to investigate the plants effect.We expect to express the plants effect on turbulence by advancing Feedback Forcing method proposed by Goldstein.

View full abstract

In this research, in order to generate the inflow turbulence, the turbulence parameters for velocities at recycle station are rescaled and introduced to the inlet boundary, while temperature is treated as a passive scalar. The generated inflow data for temperature as well as velocities are introduced into the main computational domain, where temperature is solved taking into consideration buoyancy effects. We carry out LES analysis of the spatially-developing convective boundary layer on changing earth surface roughness and temperature distribution. We discuss the necessity of considering temperature distribution.

View full abstract

In this paper, the flowfield within a building complex in an actual urban area (Shinjuku sub Center) was predicted by three different CFD codes based on different grid systems. Results of these predictions were compared with the results from field measurement and wind tunnel test. The CFD codes compared here can predict the distribution of the scalar velocity at pedestrian level within the actual building complex in reasonable agreement with the measurements except for the region far from the target buildings where the grid resolution is obviously not fine enough.

View full abstract

The environmental quality of open spaces has great impacts on outdoor activities. Building form and layout can significantly affect the environmental quality of public space by inducing or diverting winds into streets and open spaces. It has been a priority in architectural design and urban planning. Undoubtedly, the study of wind effects on people is one of the focuses in the assessment of environmental quality of open spaces. This study is to apply a CFD approach in an industrial project for the evaluation of pedestrian-level winds and the associated wind effects in the open spaces.

View full abstract

Uing a 1/600 scale model of an actual built-up area in kawasaki, we conducted wind tunnel experiments to study the air pollution concentration distribution around the intersection on a heavliy trafficked roadway at ground level. The main results are follows. The concentration in the areas surrounding the main road decresed rapidly. The airpollution discharged from the elevated road spread quickly and widely.

View full abstract

Because it acts on human being directly, the prediction of dispersion process over the urban area in local and urban scale is important. Dispersion process in this scale is complicated by small eddies generated near the irregular surface. The commonly used plume and puff model caused problems on dispersion phenomenon in complicated flows, however the computational loading is low with this model. In this paper, it is the objective to determine the characteristics of dispersion over the actual urban area after making a spatially developed turbulent boundary layer over rough-wall by using LES technique and the pseudo-periodic boundary conditions.

View full abstract

The effects of roadside trees in the central part of Sendai city on outdoor thermal environments were analyzed by coupled simulation of convection, radiation and conduction. Several cases of computations, in which the pitches of roadside trees and the height of the tree crowns were changed, were carried out in this study. Spatial distributions of SET*(Standard Effective Temperature) were calculated in order to assess the thermal comfort at pedestrian level using the data obtained from the CFD predictions.

View full abstract

In this study, the authors have simulated the concentration fields within urban street canyons with variable situation of roadside tree planning in the central part of Sendai city. The gas was released from roadway of street model to simulate traffic to investigate the pollution at pedestrian level. The effects of tree arrangements on flow and diffusion fields were analyzed.

View full abstract

In Kitakyushu city, the heat island poses a problem. Then, it aimed at considering as the basic data for tying the wind direction pattern in Kitakyushu city to heat island relief. First, the data is based on the survey data of the wind direction and wind velocity in Kitakyushu city 10 points, we proved 9 wind direction pattern as the result of we explained the pattern of a distribution of the wind direction in the summer of the Kitakyushu area. Furthermore, the strength (Temperature difference of the center of Kitakyushu city and Munakata city) of a heat island was investigated every nine patterns of these. Consequently, the heat island control effect was seen by the sea breeze, and the result of the land style of not seeing then was obtained.

View full abstract

Many cities in Japan are located in the coastal area.It is guess that sea breeze is large influence on urban climate.The purpose of this study is to examine the influence of sea breeze on urban climate. Numerical analyses of mesoscale climates in and around Sendai city and Haramachi city were carried out to investigate the urban climates of a regional core city and a small local city, respectively. The influence of regional characteristics, i.e. land use, artificial heat releases and sea breeze, etc., on urban climates was examined based on the results of these analysis by considering the heat balances in total urban space. It was confirmed that the effects of sea breeze are very large compared to the effects of artificial heat releases, since the both cities are located in the coastal area in Tohoku region.

View full abstract

When Typhoon Maemi passed over the Miyako island, maximum instantaneous wind speed 74.1 m/s and minimum atmospheric pressure 912hPa were observed at Miyakojima Local Meteorological Observatory on September 11, 2003. As a result of investigating about the high wind of Typhoon Maemi using meteorological data, such as weather survey data in weather government offices and a weather radar echo charts, it turns out that the high wind were observed under the strong rain band on the west of the ring inside the double eye of the typhoon.

View full abstract

When the typhoon Maemi passed over Miyako Island, maximum instantaneous wind speed 74.1 m/s and minimum atmospheric pressure 912hPa were observed in the Miyakojima Local Meteorological Observatory on September 11, 2003. In connection with this high wind, the serious damage occurred on the Miyako Island since the 3rd Miyakojima Typhoon in 1968. Building Research Institute, Tokyo Polytechnic Institute, KAJIMA, and Disaster Prevention Research Institute, Kyoto University conducted the investigation of high wind damage. The outline of the investigation is reported.

View full abstract

Collapses of wind turbines due to typhoon 0314 were surveyed and damages of blades, nacelles, towers, foundations and controls were clarified.

View full abstract

Strong winds due to typhoon 0314 were predicted by the typhoon simulation and CFD. As a result, the predicted maximum wind speeds and directions show a good agreement with those observed at the meteorological station.

View full abstract

Typhoon MAEMI crashed into South Korea's southern provinces before dawn on Sept. 14, 2003, bringing record winds of 215 kilometers per hour, or 135 miles per hour, and heavy rains that caused landslides and floods. Trains were derailed, ships were battered and 1.5 million people were plunged into darkness after five nuclear power stations were forced to suspend operations. The storm tore into southern parts of the peninsula on Friday night (Sept. 12, 2003), crunching everything in its path before heading out to sea on Saturday (Sept. 13, 2003). The typhoon mauled South Korea's main port, Busan, one of Asia's busiest. The typhoon twisted container cranes like pretzel shapes, shredded seaside shops, overturned cars, and buckled roads and bridges. Electric signs showered sparks over pedestrians hunched under blown-out umbrellas on flooded streets. Most of the deaths were due to electrocution, landslides and drowning. Tidal waves heaved an evacuated cruise liner onto its side on a beach in Busan. The typhoon landed when the tide was full, causing even bigger damages. Boats were tossed against each other in the storm. At least 82 vessels sank in huge seas. The typhoon halted operations at four nuclear power plants, cutting electricity to 1.4 million homes, as the country celebrated the three-day Thanksgiving festival of Chusok. Power was restored to all but 140,000 homes by Sunday afternoon Sept. 14, 2003.Eight huge cranes at the Port of Busan felled down. It is know in public that it will take more than a year to recover from the aftermath of Typhoon MAEMI.The storm left 131 people dead or missing. About 10,975 people had to be evacuated.

View full abstract

Few reports have referred to relations between wind speeds and the progress of residential damage. This paper reports on some effects of strong wind on residential damage rate caused by Typhoon Bart, 1999, using the wind speed data of NeWMeK in the Kyushu area. The authors have revealed several relations between the wind speeds and the rate of residential damage. It is found that the rate of damage has more dominant relation to maximum gust speeds rather than maximum wind speeds and the larger fluctuation of wind speeds causes the higher residential damage.

View full abstract

Strong wind is really a problem that is directly relevant to a safe operation of trains. There have been about thirty wind-induced accidents of train/vehicles since transport service was started in 1872. The regulation rule for train operation was revised frequently after the accidents. Then in strong wind areas hardware measures like wind fences have been installed on railway lines to improve the safety of train operation after the Amarube Bridge accident in 1986. This report presents the regulation of train operation and measures against strong winds in railway lines.

View full abstract

Multiple fires may break out simultaneously with or immediately after a large earthquake. They may result in a large urban fire. In particular, many firebrands may occur under strong wind conditions and disperse to distant places, thereby engendering spreading damage by leaping flames. Past records of large fires indicate that roofs are most likely to suffer damage from leaping flames. The probable reason is that roof tiles fall off and wood portions that constitute a roof are exposed just after a large earthquake. Therefore, this study made an aerial photography analysis on roof tile falling after the Kobe earthquake, and also conducted Fire Wind Tunnel experiments to investigate leaping flame damage on roofs with roof tile deficit.

View full abstract

Factors that cause spreading of urban fires among buildings are flame contact, radiant heat, convective heat, and firebrands. There are many cases in which firespread is caused by leaping flames resulting from many firebrands in places that are distant from the fire outbreak site, especially under strong wind conditions. Firebrands and leaping flames caused by them are important factors to clarify the mechanism of urban fires. Nevertheless, their systematic engineering study has not been greatly implemented because of limited availability of limited experimental facilities.Therefore, the authors performed a Fire Wind Tunnel experiment using a real-scale fire preventive wooden house to investigate firebrands. This study is aimed at quantitatively and qualitatively elucidating the chronological relationship of fire evolution and firebrand generation.

View full abstract

Since the conclusion of WTO/TBT agreement, the respect for the international standards and specifications of industrial products based on performance are considered significant aspects for civil engineering design codes. In this paper, performance based design in civil engineering area are reported. Special focus is on the development of comprehensive design codes. 'code PLATFORM ver.1' developed at JSCE and 'Geo-code 21' at JGS are introduced.

View full abstract

Overview of performance-based design such as NKB level system was given first and revision Japanese Specifications for Highway Bridges was introduced. Then re-organization of Wind Resistant Design Manual for Highway Bridges into performance-based design format was tried. Finally, Guideline of performance-based design of steel civil engineering structures published by JSSC was introduced.

View full abstract

After determinating to apply the Performance Based Design for Biilding Standard Low in Japan,Engineera started to study about the Performance Based Design.And also the Structural Engineers tried how they showed the crients the merit of the performance based design.JCSA made the guideline to Safe Buildings . In this paper the JSCA Performance menu and many methods and tools which are being used for crients as the clarification of their needs are introduced .

View full abstract

This paper describes the fundamental characteristics that cause a football to spin and the aerodynamic forces acting on a soccer ball during flight. The ball impact process of top view image was analyzed with a high speed video camera running at 4500 frames per second. Wind tunnel tests with a full size model were carried out to measure the aerodynamic forces (drag, lift and side force) on a spinning soccer ball as well as those on a non-spinning ball. It was found that the drag coefficient is almost independent of the spin rate, while the side force decreases with increasing the spin rate. This decrease could be explained by the Magnus effect produced by the spin. Visualization study by the oil flow experiment was also carried out. The boundary layer separation occurs around 130 deg.from the frontal stagnation point at 30m/s.

View full abstract

A non-spinning punted ball sometimes fluctuates during flight like a knuckle ball does in baseball. This has been recognized by players as a mysterious phenomenon. We have carried out wind tunnel tests to measure the aerodynamic forces on a non-spinning rugby ball. It is found that the side force coefficient is almost 0 at the angle of attack alpha=0 degrees. There is a cycle at alpha=30 degrees during one rotation of the seam. However, it appears needle-like at alpha=90 degrees. There are 4 cycles during one rotation. This phenomenon might be caused by the 4 corners of the rugby ball on the basis of oil flow experiments.

View full abstract

Knuckle ball is famous for being thrown by Tim Wakefield , Boston Red Sox. By the past research , it is checked that the knuckleball is carrying out the sidespin which below 1 [rps] carried out slowly. However , recent years a knuckleball is the thing of the new model which carries out a gyrospin. First , the flutter equation by theory is drawn. Then , a flutter experiment is conducted. From the result , the mechanism of change of a new – type knuckle ball is explored in this research.

View full abstract

In golf, carry is an important element and the surface structure of a golf ball affects carry greatly. Therefore, the dimple is given to the golf ball surface. Although there is a report of the experiment about the flying characteristics of a golf ball in old research, a report of the flying characteristics of the ball to which dimple structure was changed intentionally is seldom found except an author. Authors have reported that there is an effect which clarifies the dimple at the time of un-rotating and rotation and the relation of drag characteristic, and decreases a drag by the dimple from this until now.For that reason, in this research, the difference between the number of dimples at the time of un-rotating and rotation and the depth aims at showing clearly what influence it has on the flying characteristics.

View full abstract

The golf ball in flies is greatly influenced of the natural style.In this research, three kinds of golf balls marketed are used, the aerodynamics characteristic by each dimple form is searched for by wind tunnel experiment.The aerodynamics characteristic of joining the golf ball which carries out high-speed rotation in an air current is measured.And when a wind blows, in order to be able to perform the exact simulation of distance which flew,The influence of a 3-dimensional air boundary layer is put into a 3-dimensional flies orbital equation, and flies orbital analysis is performed.And an actual hit ball experiment is conducted on the seashore, and it verifies by comparing a calculation value with measured value.

View full abstract

We reported on the features of wind fluctuation for wind power energy in Kyushu area, based on NeWMeK data.
As an index of the wind fluctuation, we defined the deviation for 10 minutes of wind speed divide by daily average wind speed as the daily-averaged intensity of turbulent. The wind speed fluctuations are small at most of coastal points.
As an index of wind direction fluctuation, we used the appearance ratio on wind axis. The wind direction fluctuations are small in mountainous areas.The wind characteristics of each observatory differ by the influence of local terrain. On the coastal areas, the wind speed fluctuations are small and the wind directions are not stabilized. In the mountainous areas, the wind directions are stabilized. And the wind speed fluctuations are not small.

View full abstract

In this study, meso-scale atmospheric simulation with a horizontal resolution of 2km was performed for the offshore of Kanto region, Following conclusions were obtained.
1.Wind velocity increases as the distance from the shore increases. However,Even when the distance from the coast is constant, annual average wind velocity differs considerably depending on site. This indicates the importance of careful wind climate assessment.
2.Wind energy potential at the offshore of Kanto region is 277TWh/year, which corresponds to 94 percent of total power supply of Tokyo Electric Power Company.

View full abstract

In this study, offshore wind energy potential at Kanto region was evaluated considering technical, social and economic limitation with geographical information system.
Following conclusions were obtained.
1.Wind energy potential is only 0.4 TWh/year when the bottom-mounted support structure is used. The use of floating support structure increases the potential to 94 TWh/year.
2.The floating support structure should be designed to fit the water depth of 20m- 200m.
3.Floating type wind farm meets business promotion criterion when depreciation period of support structure are longer than 50 years. For this reason the development of floating support structure with life span over 50 years is expected.

View full abstract

We measured the visualization of the airflow around the micro wind turbine using PIV measurement. The diameter of a micro wind turbine is 500mm. This paper shows the knowledge acquired below at. 1) The micro wind turbine is generated using the airflow that blows through it efficiently. 2) The slowdown of the wind speed in the lee back of the wind turbine shows high efficiency.3) The wind velocity ratio that flows from the end of blade becomes 2.0 or more in the lee side back of the micro turbine.

View full abstract

We have developed a new wind turbine system that consists of a diffusershroud with a broad-ring brim at the exit periphery and a wind turbineinside it. The shrouded wind turbine with a brimmed diffuser hasdemonstrated power augmentation for a given turbine diameter and wind speedby a factor of about 2-3 compared with a bare wind turbine. This is becausea very low-pressure region due to a strong vortex formation behind the broadbrim draws more flow to the wind turbine inside the diffuser shroud. Torealize a greater power augmentation of it, we have investigated the optimumparameters of a diffuser open angle and hub ratio, and the optimum shapes ofan inlet shroud and centerbody. Furthermore, we have applied a new windturbine blade design based on a simple theory of an optimal wind turbine fora diffuser shroud with a brim. As a result, the new wind turbine hasdemonstrated a power augmentation for a given turbine diameter and windspeed by a factor of about 5 compared with a bare wind turbine.

View full abstract

Wake-induced flutter was observed on the hanger cable of the Akashi-Kaikyo Bridge. In this study, CFD analysis on twin cables was conducted and the results were examined comparing with wind-tunnel study of the hanger cables.

View full abstract

This study aims to clarify the generation mechanisms of rain-wind induced vibration of cables on cable-stayed bridge by wind tunnel test. The detail vibration mechanisms have not solved yet, because of the complex flow condition around the cable, which is caused by the cable inclination and the water rivulet. In recent research, it is often thought that the moving water rivulet plays an important role on the inclined cables vibration. For the purpose of investigating the effect of the moving rivulet, we measure unsteady aerodynamic force on the assumption that cable torsional motion is equal to the rhythmic movement of the water rivulet. We also compare lift force calculated from aerodynamic derivatives to the one from quasi-steady theory, and we investigate the characteristics for various positions of water rivulet.

View full abstract

Aerodynamic vibration of stayed cables, especially rain-wind induced cable vibration, has been a rather serious problem on the design of cable-stayed bridges. This well-known phenomenon occurs at particular high reduced wind velocity regions and under raining condition. From results of wind tunnel tests, it might be explained as a vortex-induced vibration, which occurs at limited high reduced wind velocity. Then, in this study, the effect of non-uniform water rivulet on the vortex-induced vibration at high reduced wind velocity is investigated by wind tunnel tests. The artificial rivulet is non-uniformly attached on a rigid cable model along the axis. Under various combinations of rivulet location, the velocity restricted response, which is similar with the observed response of the prototype inclined cables in rainy day, is obtained for the symmetrical combination of rivulet location. The conclusion is that the rain-wind induced vibration would be caused by the span-wisely non-uniform and particular locations of upper water rivulet on a cable surface.

View full abstract

Already achieved progress for stabilizing flutter was mainly come from consideration of flutter derivatives, in other words, shape of bridge section. If we review the basic equation of aerodynamics, there are not only derivatives but also mass M, moment inertia I and frequency ratio between torsional and heaving motion f0/f0 will make an influence of structure response. In this paper, effects of these dynamic characters to bridge aerodynamics are discussed. The models used in this study are rectangular sections with side ratio B/D=5, 8, 10, 12.5, 15, 20. Calculation shows that changing M and I will make a significant influence of damping value. The effect of flutter onset velocity will depend on body bluffness. The more streamlined body is, the larger effect will be achieved. Increasing frequency ratio will enlarge flutter onset velocity and stabilize bridge section. The trend does not depend on body bluffness. For each section, it is obviously detected.

View full abstract