For further optimization of the method of operation control under strong winds in the railway field, authors have been studying models which can handily estimate wind direction and wind velocity at an arbitrary point in an operation control section by using data of wind directions and wind velocities observed with one anemometer. The cross-correlation between wind velocities of two points and wind directions of two points were examined by using strong wind data.As a result, the decrease rate of the cross-correlation function of the wind direction with the increase of lag was larger than that of the wind velocity regardless of the wind direction.

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To prevent railway vehicle accidents caused by strong wind, railway companies are taking measures against strong winds. To evaluate these measures, we study methods to estimate the safety of trains under strong wind quantitatively. Overturning accidents of train vehicles are caused by instantaneous wind speed and critical wind velocity depends on angles between natural wind direction and train running direction. Therefore, to evaluate the safety of train, we calculate probability that maximum instantaneous wind speed exceeds critical wind velocity for overturning with considering natural wind direction.

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Recently, tall buildings with unconventional configuration have been designed and constructed over the worldwide area. To rational wind-resistant structural design, configurations of building shapes have been studied by many researchers in past several decades. However, wind environments around tall buildings have been rarely studied. The objective of this study is to find some critical phenomenon for pedestrian level wind
environments of tall buildings with unconventional configuration through wind tunnel tests.

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The progress of heat island effect and pollution by traffic emissions in urban streets has been serious problems. To avoid more serious situations and create more comfortable outdoor environment, the analysis on the influence of building and urban configurations has been required. As one of the building configurations which have large impact on above and inside urban street canyons, the influence of various roof shapes was investigated experimentally and numerically. But although many different combinations of roofs have been studied, the impact of the slope of slanted roofs on flow and dispersion has not been investigated systematically yet. Also, the influence of roof shape on urban ventilation has not been analyzed yet. The objective of this study is to investigate the influence of roof slope on (1) flow and dispersion inside the street canyon and (2) urban ventilation using LES (Large Eddy Simulation). The vortex structures of the cases which have peculiar flowfields were analyzed by POD analysis using LES results.

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Author performed large eddy simulation of simplified urban arrays to clarify statistical characteristics of wind speed at a pedestrian level, and the followings are obtained. (1) Probability density of wind speed at a pedestrian level can be expressed almost universally among several geometries by defining stochastic variable normalized by mean and standard deviation of wind speed except for the range of strong wind. (2) Gust factors defined by the wind speed exceed a criteria were calculated based on the probability density. These Gust factors give acceptable estimation of strong wind speed.

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It is difficult to predict the dispersion in urban area accurately. This study aims to verify prediction of pollutant concentration in urban area based on wind tunnel experiment and numerical simulation. For this purpose, field measurements of gas dispersion and wind characteristics were conducted in the campus of Tokyo Polytechnic University for two days. From the results, even the difference in direction of the wind of around 10 degrees was shown to vary in a tendency of concentration and wind velocity distribution.

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The wind tunnel experiment was carried out under the condition of field measurements. In the experiments, an approach flow of the category surface roughness IV was adopted. Three wind directions were selected based on the condition of field measurements. A high speed total hydrocabon analayzer and three type of split film probe were used for measurements of concentration and wind speed, respectively. The normalized non-dimensional concentration and the wind speed ratio obtained by the wind tunnel experiments agreed well with the field measurement data. It is found that the variance of wind direction effect on the distribution of concentration and wind characteristics.

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This study aims to verify prediction of pollutant concentration in urban area based on wind tunnel experiment. For this purpose, wind tunnel experiments and filed measurements of gas dispersion were conducted in the campus of Tokyo Polytechnic University, and their results were compared. In addition, wind tunnel experiment was carried out under various conditions of wind velocity and pollutant emission rates to confirm similarity law. The normalized non-dimensional concentration obtained by the wind tunnel experiments agreed well with the field measurement data. It was also confirmed that the normalized non-dimensional concentration was nearly independent of wind velocity and pollutant emission rate.

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This paper performs the Computational Fluid Dynamics(CFD) for predicting flow and dispersion fields in actual urban area, and validate the predictive accuracy for CFD compared with the wind tunnel experiment. Wind tunnel experiment and CFD were conducted in the Atsugi campus of TokyoPolytechnic University. In this study, the CFD model is based on the LES. Mean wind speed and mean concentration estimated by LES are in good agreement with wind tunnel experiment.

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Understanding flying path of birds is very important to design of certain type of structures such as wind turbines. In this study, as a first step, tracking of crows in Yokohama National University is made using GPS sensors attached to several crowsand those fying path is understood.

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This paper describes the characteristics of wind loads on a bottom-mounted offshore wind turbine tower for a propeller-type wind turbine with three blades (Hub height: 80m, Rated power: 2.4MW) in the feathering condition. The wind loads based on field measurements were investigated using strain-gauge data. As a result, the maximum wind loads for the wind of the landside were bigger than those for the wind of the seaside under the influence of the land about 3 kilometers away from the wind turbine. The gust effect factors for the wind of the seaside were from 1.8 to 2.0 (=category of surface roughness I-II). Furthermore, the gust effect factors for the wind of the landside were more than 2.1 (=category of surface roughness III) in range of less than 30m/s.

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In this study, numerical simulation for the load estimation on the support structures during the operation of wind turbine was validated by measurement and the load characteristics of the support structure were investigated. The simulation shows good agreement with the measurement in terms of fore-aft tower base moment. The fore-aft moment on the tower shows maximum value at rated wind speed at the base of the tower, while at the tower top, the maximum load is observed at the cut-out wind speed. This is because the fore-aft moment is dominated by the thrust force on the rotor at the tower base while dominated by the moment on the rotor at the tower top.

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From 2013, Tokyo Electric Power Company, and “New Energy and Industrial Technology Development Organization’s” started research project of offshore wind condition, off the coast of Choshi. This paper explains the influence of observation tower.

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From 2013, Tokyo Electric Power Company, and “New Energy and Industrial Technology Development Organization’s” started research project of offshore wind condition, off the coast of Choshi. This paper explains observation performance of the Doppler LIDAR.

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In this paper, the effect of atmospheric stability on wind turbulence intensity was examined using the meteorological data observed at 3.1km offshore from Choshi. In this study, to avoid turbulence generated at land, observation data in offshore wind direction was used. The results of this study are summarized as follows1) In offshore wind direction, atmospheric condition was always stable in summer, and unstable from afternoon to night in winter.2) Turbulence intensity under stable atmospheric condition was smaller than under unstable atmospheric condition in offshore wind direction.

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In this study, offshore wind climate assessment was carried out by using mesoscale model and validated by measurement at an test site located 3.1km offshore Choshi. It was found that wind climate in Japan coastal region was strongly influenced by nudging, land use, sea surface temperature (SST). A method to identify optimal nudging using offshore and aerological observations was proposed. The land use datasets were created using max area sampling method according to horizontal resolution of mesoscale model. The SST datasets were corrected by using observations.

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From FY2012 to FY14, in development of site conformity assessment procedures related to wind energy system, a site conformity assessment method for the wind turbine installed at a specific site has been  developed. In this paper, the site conformity assessment method related to the wind conditions at specific site basing on the Guidelines for Design of Wind Turbine Support Structures and Foundations [2010] is shown. As evaluation method of turbulence intensity, the computational fluid (CFD) analysis was applied and the results of comparison and verification of the field measurement data are shown.

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For the purpose of evaluation of numerical site calibration using CFD, the uncertainty analysis of measurements on complex terrain was conducted.
Ichiki Kusikino site are selected for this study. In Ichiki Kushikino site, the measurement campaign carried out in NEDO project.

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The wake of a wind turbine generator (WTG) operated at the optimal tip speed ratio is simulated by using a large eddy simulation (LES) technique. In the present study, undulating motions are observed in the wake at downstream distances larger than approximately 5D (D : rotor diameter of WTG).

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Blade tip displacements of a real medium size wind turbine were measured with a 3 dimensional motion analysis software using high-speed video image. By studying different calibration methods, the measurement with error less than 20% seemed to be possible. The responses of three bledes were similar one another, and it was affected by the change of the aerodynamice force when it passed in front of the tower. In order to clarify the blede response characteristics and to obtain the information to improve the accuracy of the response analysis, more study seems to be necessary with more measurements.

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The United States announced the improved Fujita scale (Enhanced Fujita Scale) for 2,007 years for the purpose of breaking off the true damage in the past Fujita scale and estrangement with the estimated wind velocity. Canada announced the improved Fujita scale (Enhanced Fujita Scale) in 2013 for the purpose of being similar. In our country, I collaborated country technique policy research institute, Building Res. Inst., Meteorological Research Institute, Tokyo Polytechnic University for the purpose of the development of the improved Fujita scale than 2011 for Japan. On the improved Fujita scale for Japan, I took the technique to demand the estimate wind velocity for engineering using the numerical value by experiments by a proof stress and the velocity of the wind such as buildings. In addition, Fujita scale rank fixed a wind velocity range to distributing it and adopted technique to renew degree of the damage depending on the wind resistance ability such as buildings.

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This paper illustrates outline of degree of damage and corresponding wind velocity estimation in the case of Timber Residences, which will be aimed to contribute to the development of Japanese version of Enhanced Fujita (EF) Scale. First, the authors organized eight degrees of damage (DODs) on the basis of past damage examples. Second, in order to estimate instantaneous wind velocity corresponding to DODs, load test data of timber roofing components and clay tiles and horizontal deformation performance of structural components were used respectively.

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Japan Meteorological Agency has modified their statistical policy on tornadoes and tried to figure out the actual condition from then. In US, to append damage indicators and to fix inconsistency of rating tornadoes and overestimate of wind speeds, Enhanced Fujita Scale was proposed and commonly used nowadays. In Japan, to make clear the actual situation of tornadoes and describe their intensities and effects to buildings and other structures, review and improvement have been started for the Fujita Scale considering typical Japanese climates and other situations. In this report, structures other than buildings were selected as damage indicators (DI) of tornadoes, and basic concepts to evaluate their degree of damage (DOD) and corresponding wind speeds were explained.

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This paper discuss about the development of Japanese Enhanced Fujita Scale for DOD and corresponding wind speed of non-residential structure (vehicle, container and vending machine).

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As the classification method of the intensity of tornado, appropriate Damage Indicator and Degree of Damage should be proposed.  In this study, to fix these parameters, the tornado-damage estimation technique will be established.  Then it will be helpful for laying down the Japanese Enhanced Fujita Scale.  In this report, the critical wind speed for some kind of damage type of ‘the sign board’ and ‘grave stone’ which is selected as the DI, was estimated.

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We suggested a list of DI and DOD for tree that is a part of enhanced Fujita scale to estimate the intensity of tornadoes. The indicator of tree is one of main indicator in natural  environment, in the relatively weak range of tornado intensity and common indicator that is expected to be used in worldwide.
We compared the critical wind speed for growing environment, forest, park, garden and along road. The roadside trees were estimated to have averagely higher critical wind speed. The reason was considered that the management by human to restrict the size of crown and the height. The values in the list were considered to be adequate to  former reports that demonstrate critical wind speed for trees.

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In this study, wind speed to make a road damage was discussed considering terrain effect. Considering the equilibrium state of the weight of road, adhesion strength and the summation of pressure drops by a tornado and by a terrain effect, peeling of a good asphalt layer start at 75 m/s for a flat terrain. On the other hand, the wind speed to make. a road damage for a steep terrain distributed in the range of wid speed from 66m/s to 75m/s. Moreover, a DI (Damage Index) for a road damage and its DOD (Degree of Damage) were presented.

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Damage indicators for the estimation of gust wind speed were examined in order to evaluate the intensity
of  tornado or downburst and so on. This aims to contribute the establishment of Japanese Enhanced Fujita Scale for the good estimation of the strong wind damage by tornado or downburst. Degrees of damage were proposed for some construction’s elements and an example for a damage indicator, “standard Japanese roof with ceramic tiles”, was presented.

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For nuclear power plants located along the coast line, tornados are one of the severe meteorological events to be considered, because most of tornados were observed near the coast in Japan. This paper discusses about a tornado wind hazard evaluation method near the coast area.

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On the midnight of 16 September 2013, a severe thunderstorm passed over Midori and Kiryu City in Gunma
Prefecture, causing a F1 tonado damage. The change of surface pressure was observed by high dense ground observation network POTEKA. The tornado and misocyclone pressure fields are estimated by using the modified Rankine vortex. The result of this analysis shows that we need to discuss the upper air misocyclone and surface tornado.

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Meisei Improved developed low-cost compact weather sensor "POTEKA" in 2013. The following year, we further improved POTEKA to observe wind direction, wind speed and rainfall. Additionally, we can obtain real-time meteorological information (temperature, pressure and etc.) per one minute in total 145 stations. Downburst occurred in the August 22 2014 (case 1), POTEKA could capture the temperature drop and pressure peak. In comparison with the case of downburst on 11 August 2013 (case 2), temperature decrease rate is about half, after the pressure peak was maintained a high pressure state. In addition, thickness of cold air flow of case 1 was estimated lower than case 2 about a few tens of meters.

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The present study aims to revise hazardous wind watch issued by JMA. We analyzed the characterictics of misocyclones in clouds observed by Muroto Doppler radar from 2008 to 2013 and compared between tornadic and nontornadic misocyclones. We detected 50 misocyclones. 80% of them were borned offshore and 33 vortices landed. All tornadic misocyclones also were borned offshore and then landed. The lead time until landfall was more than 10 minutes. The tornadic misocyclones also have the tendency to grow up higher. The hazardous wind watch can be revised based on the knowledge of these characteristics.

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The scoop pictures of tornados taken by citizens are frequently introduced by television news. We reported the photogrammetric method which measures correctly the three-dimensional positions of tornadoes by funnel cloud image and its measurement example (2014). The space coordinates of the tornado location were evaluated from the measurements of the azimuth angle of camera, the elevation angle of camera, and the length of epipolar line between the camera and the tornado. An unsolved problem was that the picture was distorted due to the elevation angle of camera. In this report, we explain the solution for this problem.

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Wind-induced vehicle accidents sometimes occur on bridges, embankments, and so on. In this research, aerodynamic force contributing to overturning is examined by wind tunnel experiment, CFD analysis and field observation. Aerodynamic coefficient of a rectangular prism is derived to evaluate aerodynamic force, and it takes the effect of boundary layer near ground surface into account. By wind tunnel experiment, when wind condition acting on moving vehicle changes suddenly due to crosswinds, transient aerodynamic characteristics is examined, and inditial response function to approximate the characteristics is evaluated. Finally, we considered about the difference between wind condition data measured on a fixed point and a moving vehicle.

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The generation of tornado-like flow with horizontal shear was carried out by a numerical fluid analysis.Effects of the inlet outlet height, upward flow opening width, the size of the analysis area, the strengths of the shear, and upward flow on the flow field were investigated.As results of this study to generate of realistic tornado-like flow varying spatially and temporally.Generated tornado-like flows had strongly two-dimensional behaviors and the distribution of tangential wind speed fit to the thoreticalformula for two-dimensional viscous vortex.More over, it was found that the strength of the shear controled circulation and maximum tangential wind speed of tornado-like flow.

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Currently, Fujita scale is usually used to estimate the wind speed of tornadoes from damages by them. However, this method becomes invalid when there is no damage. Therefore, other method to estimate characteristics of tornadoes independent of damages is required. In this study, the relations between characteristics of tornadoes and shapes of funnel clouds were investigated by using computational fluid dynamics technique to make a new method to estimate characteristics of tornadoes with photographs and movies of funnel clouds. As results of this study, it was clarified that humidity and maximum wind speed controlled the diameter and the height of funnel clouds respectively.

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The generative mechanism of tornado, it needs surrounding phenomenon such as large-scaled instability and convective flow field, meso-cyclone (upward and rotational flow), down draft, gust front, wind shear and surrounding temperature field. According to the previous studies about modeling of tornado, tornado simulators or meteorological simulation models were used. However, tornado simulators only consider the meso-cyclone flow and meteorological models focus on more large scale area than tornados; they are difficult to present the actual flow pattern of tornado. In this study, we focused on the simulation area below the thundercloud, mount those actual phenomena and above surrounding conditions to this model, and performed more idealized simulation.

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Liftoff and flight behaviors of tornado missiles, which are initially placed on the ground, are computed using the Fujita's DBT-77 model.  The results have revealed the dependency on the initial positions and the cumulative probability distribution of flight distance and maximum velocity.  It is found the results of the U.S. NRC guide method, where a missile is released from a specific point at 40m elevation, correspond to more than 90% exceedance probabilities.

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CFD prediction of wind pressure distributions resulting from a traveling tornado-like swirling flow is conducted.  When a tornado-like vortex travels along the centerline of a building, a large magnitude of suction peak occurs on the roof surface and eaves.  If the building has an opening on a right-side wall, the maximum peak pressure increases on a left-side wall and the magnitude of roof surface negative peak pressure decreases.  In the case of frontal-wall opening, the maximum peak and the magnitude of negative peak pressure increase along wind ward wall or eaves.

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There are so many parallel circular structures such as stay-cables bridge. Wake galliping and wake-induced flutter appear in such parallel circular structures. The research on wake galloping have been done so far, however the mechanism of wake-induced flutter has not perfectly been revealed. This research tris to crarify the relationship between the arrangement of 2 cylinders and mechanisms of these aero dynamic instabilities based on the vibration responce of the downstream cylinder gained from free vibration tests and 2 DOF flutter analysis.

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Aerodynamic noise arising from the structural member has been confirmed to occur if the member which is arranged in parallel is exposed to a small approaching flow disturbance. In this paper, the experiments and discussion were conducted on how the suppression of wind noise using a simple verification and adduct of aerodynamic sound generated from the flat bar.

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In this study, the structure of fluctuating surface pressure acting on a fixed circular cylinder was investigated by computational fluid dynamics and POD analysis. Examinations of  effects of member length in the analysis domain and member end boundary gives to fluctuating surface pressure acting on a fixed circular cylinder by numerical calculation were carried out. As results of this study, it was found that the fluctuating surface pressure acting on a fixed circular cylinder was affected by cylinder length and boundary conditions around the end of the cylinder. Moreover, POD analysis indicated that the fluctuating surface pressure acting on a fixed circular cylinder had symmetric and asymmetric mode shapes along the cylinder axis.

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In turbulent flow, the spanwise spatial correlation around a bluff body is higher than the spanwise correlation of oncoming turbulent flow. Previous studies showed that it was caused by the two dimensional spreading of flow at the transfer from oncoming flow to peel sheering layer. This research tried the modal decomposition to the flow field around a rectangular model including separated bubble with POD and DMD. POD analysis shows the process of two dimensional spreading in the separated bubble. Though this process is not appeared in DMD analysis, the dynamic process of two dimensional spreading in the separated bubble will be revealed by using more appropriate linear mapping.

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An aerodynamically stable pentagonal shape bridge deck was proposed for long-span cable-supported bridges. The top and bottom deck flow are controlled by adjusting the top deck curb position, known as separation interference method and the bottom plate slope, respectively. In this paper, it is tried to elucidate the influence of one of the flow features i.e. top deck leading edge flow separation on flutter instability. Two pentagonal bridge decks having a bottom plate slope of 11° with and without curbs were analyzed. Firstly, static two-dimensional unsteady RANS simulation was carried out for those two sections to visualize the flow filed. Then, forced vibration simulations were conducted to extract the flutter derivatives and aerodynamic damping were calculated. Finally, analytical results were compared among them.

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It is necessary to assume internal pressure coefficient, when deciding the design wind loads for cladding and components based on the wind tunnel test. This paper evaluates the internal pressure coefficients base on the field measurement and wind tunnel test. JMA-Meso Analysis wind velocity is used as the reference wind velocity. And the Analysis wind velocity is comparison with the Doppler Lidar wind velocity. The internal pressure coefficients estimated from the external pressure coefficients measured by the wind tunnel test and the wind force coefficients by the field measurement. The design internal pressure coefficients are appropriate to the net internal pressure. 

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Wind-induced interference effects on local wind loads on two buildings with various height ratios and locations of an adjacent building for all wind directions from 0°to 355°in 5°steps were studied by a series of the wind tunnel tests on typical tall building models using a pressure measurement technique. In this study, characteristics of local wind forces along nine height levels of the principal building are presented and discussed. As a result, varieties of along-wind and across-wind local force coefficients along the height levels depend on the locations and height ratios of the interfering building.

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In this research, the characteristics of large peak suction on theflat roof are simulated by use of LES method when wind direction changes. The characteristics of large peak suction are discussed, and flow mechanism causing peak suction are investigated based on the computed results.  

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The effects of roof shape on generation points of unsteady vortices and unsteady wind pressure on a body under a short-rise-time gust using a computational fluid dynamics (CFD) simulation with an LES model. The flow around flat roof, gable roof and hipped roof bodies subjected to a step-function-like gust was simulated. It was confirmed that the generation points of unsteady vortices around a body under a short-rise-time gust varied with its roof shape. The overshoot of wind pressure on the roof face was considerably large in the case of the gable roof body and wind direction of 45 degrees. On the other hand, the overshoot of wind pressure on the roof face of the flat roof body continued over a long period.

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Wind power generation has been spread worldwide even in Japan. However, it has been reported damage collapse accident of windmill wind power generation facilities in Japan, and it has become a major problem. In the development of wind power installation, wind conditions in Japan are seriously problem for wind gust and typhoon effect and so on. In addition, overturning and torsional moment effects for wind turbine tower structure are very important for collapse trigger. In this study, moment and load for wind turbine structure were examined for changes in overturning moment and torsional moment in simulated natural wind. In considering the similarity law, it was revealed for generalized moment and load characteristics.

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Wind tunnel tests were carried out to investigate velocity profiles behind wind barriers. 4 types of wind barriers with solidity ratio of around 0.5  was employed. The drag forces of these barriers were also examined. The net type wind barrier has uniform wind reduction and its drag force is small. The bar type wind barriers have large wind reduction around its height. Horizontal correlation of fluctuation velocity is small with any types of barrier.

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