This study investigated the pressure field of the typhoon.
By using typhoon best track bata and ground observation data,pressune parameters of wara betermined for typhoons caused from 1961 to 2010.Statistical studing was ronducted and some comparison was made with provious researchons results.

View full abstract

The basic wind speed used in a wind resistant design is average wind speed during 10 minutes in height 10-m-above ground whose recurrence interval is 50 year to100 year. The basic wind speed is illustrated as a map based on observation records of the wind speed at the observatories of Japan Meteorological Agency. As smoothing is applied to over whole Japan at once usually, the contour lines may distort a lot depending on a place. If it can devise e.g. dividing into some areas which have the same characteristics, consideration of a climate zone properly, the more suitable contour lines will be drawn. In this research, the statistical work examined zoning for observation record of the Japan whole country, focusing on the strong wind for wind resistant designs, such as daily maximum wind speeds and annual maximum wind speeds.

View full abstract

Some effects of averaging time for wind speed on a peak value are known. However, wind speeds with different averaging time are used. In this paper, we reported effects of averaging time for wind speed on intensity of turbulence under strong winds. Mean wind speeds are almost constant with length of averaging time. On the other hand, peak gust speeds and gust factors became smaller as average time became longer. As averaging time became longer, intensities of turbulence based on arithmetic average became larger because of reducing amount of data. Turbulent intensities based on moving average became smaller.

View full abstract

In this study, a forecast method of wind speed and direction was proposed.

View full abstract

We investigated the sensitivity of the aerodynamic parameters deduced by the logarithmic profile. Two methods were employed. (1) One parameter fitting based on log-law profile with fixed values of the displacement height by the centroid of momentum on block and the roughness length was determined. (2) Tow parameter fitting by using log-law profile and both of the displacement height and roughness length were deduced simultaneously. The results show the existence of low-law layer and reveled the roughness length is more robust parameter to the method of its determination.

View full abstract

In the part 1, an estimation method of a wind speed distribution is proposed in the higher wind speed range (over 5m/s). It is for using the fatigue design of apparatuses of strung wire which is generally constructed less than 20m in height. In this method, Weibull parameters are calculated based on the meteorological station data, and the Contour Graphics of Weibull parameters is drawn by the linear interpolation between meteorological stations. Moreover, this method is estimating wind speed distributions at optional area. The part 1 is evaluating the validity of observed and estimated value by using the Contour Graphics in Tochigi prefecture with this estimation method.

View full abstract

In the part 2, wind velocity distribution in higher range is evaluated from the measurement data at meteorological stations in order to estimate fatigue damage to apparatuses of strung wire. The function of  is applied because the wind speed distribution in the higher range approaches asymptotically to X axis. Parameters of  and  are identified based on the meteorological data. Furthermore, the Contour Graphics of  and  is drown in broad area, and  and  at a meteorological station point are identified. This method indicates the possibility that the wind speed distribution is estimated.

View full abstract

We experimentally simulated microbursts in water channel and measured them through PIV method, in order to clarify the reason of localized wind gust in microburst yielding localized damages. We found that the origin of localized wind gust was not boundary layer turbulence but intense concenrated downdraft without mashroom voritces. Our experimental results were comparable to actual wind gust of 30 m/s in velocity within small area of 300 m in diameter though the mean velocity of microburst of 3000 m in diameter was only 13 m/s.

View full abstract

Windbreak trees have been planted in a harsh wind environment for growth from its purpose.  Some trees have withered by their severe environmental conditions.  So we measured environmental conditions such as the wind and the sky view factor at 45 places in Tokyo including 535 trees.   Then we examined the relationship between the degree of withering and the environmental conditions.

View full abstract

The wind environment around a tall building is greatly influenced with building shape. The strong wind around tall buildings is controlled by modified corner shapes, because separated flow is controlled. So, it is expected that the building shape where a separated flow is small has an effect in control of strong wind around tall buildings. Then, authors focused on a helical- shaped building which can control a separated flow greatly in past research. In this paper, LES is carried out and investigated about the wind environment of the pedestrian level around the helical-shaped building.

View full abstract

In this study, we attempted to enable prediction of pollutant concentration in the non-neutral atmospheric condition from wind tunnel experiments and CFD simulations of neutral atmospheric condition only, generalization that expressed the effect of atmospheric stability on pollutant concentration within urban street canyons. We conducted the effect of atmospheric stability on pollutant concentration within urban street canyons from both wind tunnel experiments and CFD simulations under different atmospheric stability conditions. Similar tendencies can be found by wind tunnel experiments and CFD simulations. A “stability effect ratio” of pollutant concentration (SER_C^*=C^*/C^*_n) increased with increase in Bulk Richardson number and SER_C^* was probably independent of the locations and flow patterns. Thus SER_C^* was proposed as an index expressing the effect of atmospheric stability on pollutant concentration.

View full abstract

The authors intend to use WRF in order to prepare standard wind data at high-altitude for assessment of pedestrian wind environment. Moreover, it is going to extract the vertical profile of the typical wind velocity at the time of a summer weak wind required for the CFD analysis of air pollution, or temperature from the calculation result of WRF. In WRF, although many physical models are prepared, the sensitivity of the result depended on the difference in a model is not fully clear. Then, while each physics model investigated the influence which it has on the calculation result of WRF, comparison with observations was performed. At an altitude of 70m, some differences were seen in a calculated value and other CASE that changed only the atmosphere boundary layer process, but the difference was not almost seen at the CASE interval as altitude rose. In addition, most influences which each physical model has on the calculation result of WRF were not seen.

View full abstract

In this paper, we made ​​a comparison with the results observed with the impact on the calculation results put the urban canopy model for the calculation of WRF. The occurrence frequency of wind velocity calculated at 715m by WRF agreed very well with those of the observation data. In addition, the occurrence frequency of wind velocity calculated at 70m by WRF putting a urban canopy model agreed very well with those of the observation data. However, a difference was still seen in observation value and a calculation value at 285m. In this, because a high-rise building coexists I thought it would drag due to large. An effect was not seen in the occurrence frequency of the temperature. The reason is because it does not consider density when it classifies city forms.

View full abstract

This paper reports the feature of wind fluctuations in Kyushu area for wind power energy development,comparing wind properties based on NeWMeK data to winds by the local wind distribution map of NEDO.Our survey based on NeWMeK data on 2007 indicated that annual average wind speeds are about 3 m/s at a height of 30m through a year. And annual average wind speeds based on NEDO are higher than those based on NeWMeK. Two representative observation points were selected for minute investigation of the fluctuation property of wind speed and direction.

View full abstract

A previous study, which compared two wind fields in coastal waters around Shirahama obtained from the mesoscale model WRF and the satellite-borne synthetic aperture radar (SAR), suggests that WRF may underestimate horizontal wind speed gradient near the coastline. Thus, this study uses two in-situ wind speed measurements from the Shirahama oceanographic observation platform and the Southwest Wakayama Buoy. As a result, it is found that the horizontal wind speed gradient between the two sites is underestimated in WRF, because wind speed is overestimated near the coast while it is underestimated off the coast.

View full abstract

In the present numerical study, we carried out the large-eddy simulation (LES) of the wake generated behind the wind turbine under optimal tip speed ratio over complex terrain. Although existence of tip vortex was seen, it was shown that the structure  has collapsed quickly, due to the separated flow from topography.

View full abstract

Since Japan is surrounded by the sea, air-borne sea salt particles have a large influence on structures in coastal area. It is necessary to estimate the amount of adhesion salinity based on the concentration of air-borne salinity in atmosphere considering the wind state around a target structure for more realistic evaluation. In this study, the amount of adhesion salinity in each member of a structure was evaluated with the above matter in mind. The tendency about the amount of adhesion was almost the same between the observation and the estimation.

View full abstract

The use of the natural ventilation is effective for the evaporation heat loss by the sweat and the removal of the heat load that occurred in the room. It was investigated for cases of uniform and sinusoidal wind flows using a climate controllable wind tunnel. From the experiment, the frequency of sinusoidal wave flow affects the convective and evaporation heat loss slightly decreased when the frequency of sinusoidal wind flow increased.

View full abstract

Tsukuba tornado occurred 6 May 2012 was simulataneously filmed by many
pepople at various locations. We suggest the scheme estimating the
maximum tangential velocity and the core radius of the Tsukuba tonrado
from its figure filmed. The velocity and pressure fields of the tornado
in upper layer was adapted from those of Rankine vortex in our scheme.
The result showed that the maximum tangential velocity could be
estimated properly. The evaluation of the relationship between the core
radius of tornado and the radius of debris, however, was required more.

View full abstract

The mean trajectory of flying plate-like debris in tornado-like flow was investigated by 6DOF motion simulation of 3-D debris included flow field obtained by LES numerical fluid analysis. Moreover, the flying behavior of debris in tornado-like flow was explained by equilibrium condition of forces.
As the results of this study, it was clarified that the mean trajectory of debris in tornado-like flow was controlled by Tachikawa number defined by maximum tangent wind speed, and the relation between radius component of aerodynamic force and centrifugal force made a debri cloud.

View full abstract

Crosswind can cause an accident such as overturning of large vehicle. The existing wind speed traffic regulations only consider the crosswind as part of safety evaluation. However, there are two kinds of wind force acting on a moving vehicle in reality. The first type is the crosswind and the other type is the wind caused by the movement of itself. The safety cannot be assured if the regulations only consider the crosswind part. Therefore the purpose of this study is to determine the wind speed traffic regulations by finding the fluctuation characteristic and the probability of up-crossing rate of the wind acting on a moving vehicle.

View full abstract

This paper presents the methodology to develop high wind risk function applicable to timber residences. The proposed risk function is composed of wind hazard and fragility information on the given site and construction method. With respect to the fragility information, the past data of load tests on glass, clay roof tile, and timber frame components were applied to each fragility function. By calculating the high wind risk function as an example, it showed that the function can numerically reflect the difference of site and construction method on the degree of high wind-induced risk.

View full abstract

  Risk estimation of wind disaster based on resistance of building components is described. Almost damage due to wind storm is filure of building envelope components, rather than failure of structural frame. Risk estimation of wind disaster, therefore, is developed considering for building envelope components. Risk is calculated using event probability of storm, resistance probability of components and repair costs. Risk is represented by damage probability multiplied by repair cost.

View full abstract

This paper describes estimation of the added-mass effect of 2-dimensional square prism under aerodynamic vibration and on-set fluid velocity. In the part 1, the simulation of aerodynamic vibration, which parameters are Scruton number, the ratio of density and the damping factor, is conducted by means of the improved hybrid aerodynamic vibration technique. From the result, response curves and variable lift coefficient are evaluated and discussed. In the response curves, the on-set fluid velocity gets lower, the ratio of density gets bigger. The variable lift coefficient under aerodynamic vibration decreases with increasing the response under vortex-induce vibration, and the coefficient has smallest value when the response has maximum value.

View full abstract

In the part 2, in disaggregating the external force to the coordinate phase between external force and acceleration response and the coordinate phase between external force and velocity response under harmonic vibration, the coordinate phase between external force and acceleration has the effect of added-mass to vibration system. This phenomenon is drawn on the complex plane based on dynamic equilibrium of forces. Based on the idea of added-mass effect, the added-mass coefficient is driven and non-dimensional fluid velocity and Scruton number is formulated by using the added-mass coefficient.

View full abstract

In the part 3, the ratio of the natural frequency and predominant frequency and phase angle between external force and acceleration response are discussed. The ratio of frequency has constant value in the range of vortex-induced vibration. It is speculated that the Lock-in phenomenon occurs. The phase angle increase with non-dimensional fluid velocity in the range of vortex-induced vibration. In the higher range which Galloping vibration occurs, the phase angle gets smaller. From the result, the assumption of added-mass effect is possible in the case of quasi-stationary.

View full abstract

In the part 4, the non-dimensional fluid velocity which the vortex-induced vibration is evaluated based on the idea that the response curve for non-dimensional fluid velocity which is derived by the added-mass coefficient. From the evaluation, it is possible to evaluate the non-dimensional fluid velocity of vortex-induced vibration.

View full abstract

Spatial correlation of fluctuating lift forces on square cross section in smooth flow and in isotropic turbulence were analyzed by LES, and compared with the result of experiments conducted by Vickery. The isotropic turbulence was generated based on 3D energy spectrum in the wave number space. Spatial correlation became negative value due to the lack of long-term fluctuations when the wave number space was too small. The isotropic turbulence should be generated in the space which is 20 times larger than the turbulence scale in order to satisfy the spatial correlation of fluctuating wind. The analyzed spatial correlation of fluctuating lift forces showed well agreements with the results of the experiments both in smooth flow and in the isotropic turbulence. 

View full abstract

When we measure low-frequency noise in outdoor, we attach a spherical wind screen to a measurement microphone in order to prevent the effect of wind. In our former study, it was suggested that instantaneous change of flow field around sphere affected measured result. Therefore, we conducted surface pressure measurement of spherical model. Under constant wind speed condition, the flow separated at 60 degree, and the negative pressure on the downstream side from 90 degree became constant. Under rapidly changed wind speed condition, sudden change of back pressure was confirmed. At this moment, a vortex was probably formed behind the model. The pressure near the separation point reached its peak slightly later than that of wind velocity.

View full abstract

It is known a wind force acting on a structure under a gust with a very short rise time occasionally reaches a large value not seen in a steady wind flow. In this paper, the properties of unsteady wind force on bodies with gable roofs of two different pitches were investigated using a tunnel test. It was found that the overshoot coefficient decreased with an increase in non-dimensional rise time. The rate at which the overshoot coefficient reduced was different depending on a roof pitch of body. The overshoot phenomenon of the lift acting on a 1/4-pitched roof body occurred in bigger non-dimensional rise time than a 1/2-pitched one.

View full abstract

In flutter analysis, Signature turbulence, gust forces and motion-induced forces acting on structures are often treated by summing so far. But it’s beneficial to analyze focusing on motion-induced forces since it’s conceivable that only motion-induced forces affect vibration of structure. So, this research aimed to add method for extraction of motion-induced forces as a trial. As a result, motion-induced forces can be separated from the entire forces indeed, and evaluations by both seem almost consistent. However, this theme needs to consider deeper continuously.

View full abstract

On the 2-dimensional rectangular cylinders, it is known that the galloping will occur under particular side ratios, but there are few researches about the galloping of rectangular cylinder under oblique wind. Using inclined rectangular cylinder models with various side ratios, the wind tunnel tests and flow visualization experiment were conducted. Then, it is found that some cases become unstable state against the galloping by changing the wind direction. It can be said that the main reasons are changes of side ratios due to inclined rectangular cylinders and effects of 3-dimentional flow behind the rectangular cylinders such as axial flow.

View full abstract

Wind tunnel testing on aerodynamic sound from perforated metal was conducted. Sound pressure level and peak frequency were analyzed. Firstly, experimental setup was customized for targeted aerodynamic sound. The sound was measured at angle of 80 degree, with wind speed of  less than 12.5 m/s. Peak frequency around 1 kHz is proportional to wind speed, which depends on hole diameter.

View full abstract

This research focuses on the in-line vibration clearly observed among the certain wind speed at the pylons of Hakucho Bridge. To reveal its cause and characteristics, wind tunnel experiment was conducted. In the experiment, the displacement of tower and the air flow which hit on the tower of downstream were measured. As a result, when we can see the harmonic vibration, the frequency of vortex is almost equal to natural frequency of the model. After that, we changed the distance of the model, and tried some cases the same way, which turned out that we could see the in-line vibration at the certain distance of the tower.

View full abstract

In order to suppress wind-induced vibrations of bridge girders, there are two primary methods applied to real bridges: aerodynamic countermeasures and mechanical countermeasures. In this study, a new approach, "a dielectric barrier discharge (DBD) plasma actuator", was investigated through wind tunnel experiments to determine its potential as a device for flow control around bridge deck sections. This approach is already in use in other fields, such as in the fluid dynamics flow for separation control in wing surface flow. It was found that there is a possibility that DBD plasma actuators could be used in the future in devices for suppressing wind-induced vibrations of bridge girders.

View full abstract

A condition monitoring method of wind turbine using aeroelastic model and SCADA data has been proposed. In this method, modeling of wind turbine is important as wind response of all parts of structures is obtained by calculation. In this study, a physical model which represent detail parts of drivetrain is proposed and validated by comparing the natural frequencies obtained by measurement data. And using this new model, damping ration of 2nd mode of wind turbine is determined by system identification. Obtained value was 2.5% which is as much as 4 times the value used before, and agreed well with vibration test result.

View full abstract

In order to validate quasi-steady aerodynamic force model, which is generally used in a galloping simulation of overhead transmission line, 3 DOF vibration tests with large amplitude at low frequency in a wind tunnel were performed using a sector model of four-bundled conductors. In the galloping simulation, by considering the quasi-steady aerodynamic forces acting on sub-conductor, the aerodynamic force due to torsional velocity can be formulated, which is not included in the quasi-steady aerodynamic force formulated for the whole four-bundled conductor model. Results of time history analysis for the experimental model without the aerodynamic force caused by torsional velocity differ drastically from the test results. On the other hand, results of time history analysis for the model considering the quasi-steady aerodynamic forces acting on the sub-conductor show similarity to the test results.

View full abstract

In FEM analysis, linear and non-linear buckling analysis and time-history response analysis are carried out targeting the steel circular cylinder. It was indicated that the buckling behavior can be estimated safely by using mean wind force coefficients averaged in vertical direction. Especially, it can be investigated by linear bifurcation buckling analysis or theoretical analysis based on uniform external pressure. From the results of a time-history response analysis, the dynamic effect of fluctuating wind loads on the stress involved in the wall is made clear. The gust effect coefficient is proposed by the ratio of the wind force coefficient at the stagnation point.

View full abstract

The purpose of this study is the response prediction of multi-mass system under fluctuating wind force in elasto-plastic range. As basic research, this research verifies whether prediction method proposed for one-mass system can be adapted for multi-mass system. It is based on time history response analysis. From the analytical results, it is recognized that prediction method proposed for one mass system can be adapted for many mass system.

View full abstract

The number of the isolated high-rise building has been gradually increasing in Japan. However, the full-scale researches about the wind-induced response of the isolated structures are not sufficient. We are concerned about the isolated structures based on new technology which will encounter with the huge typhoon and result in large damage. Thus far a long-term monitoring to wind velocity and response of 20-story isolated building with an elongated section has been executed. This paper discusses the characteristics of wind-induced response for this isolated building using the monitoring records. Main focus of this paper is the stiffness evaluation of base-isolation layer based on observation data.

View full abstract

Wind force on roof tiles of a house with gabled roof was measured in wind tunnel.
 Main purposes of this study are to investigate lateral peak wind force coefficient acting on the ridge tile.
 In this paper, lateral peak wind force coefficients for ridge tiles were proposed.

View full abstract

Wind force on roof tiles of a house with gabled roof was measured in wind tunnel.
 Main purposes of this study are to investigate peak wind force coefficient given by a difference between pressure on a surface of the tile and pressure on the underside of the tile.
 In this paper, characteristics of the peak wind force coefficients of the tiles with various gaps between tile and sheathing roof board were presented.

View full abstract

In order to is to investigate the characteristics of time and space-Averaged Estimation of peak negative pressure, the LES method is applied to the flow around a three-dimensional square cylinder in boundary-layer turbulence. First, the computed results for negative peak coefficients are compared with experiments. Next, based on the computed data, relationships between time-averaged and space averaged peak values are investigated. 

View full abstract

 In this paper, the design wind force coefficients of the vertical flat plates attached to the outer walls of high-rise buildings are discussed.
 Based on the wind tunnel test results, the net wind force coefficients obtained from the difference between the pressures on the both side of vertical flat plate are compared with those predicted form the pressure coefficients at two points near the vertical plate on the wall.

View full abstract

With the increasing use of solar photovoltaics, wind-induced loads on rooftop solar arrays
have become a problem due to the lack of design provisions in wind loading standards and codes of
practice. A series of wind tunnel experiments have been performed to evaluate wind loads on solar
panels on flat roofs, mainly focusing on module forces calculated from area-averaged net pressures on solar modules of a standard size. In order to investigate the module force characteristics at different locations on the roof, solar array models, which were fabricated with pressure taps installed as densely as possible, were moved from place to place. Design parameters including tilt angle and distance between arrays, and building parameters including building depth and parapet height, have also been considered. The results show that unfavorable negative module force coefficients for single-array cases are much larger than those for multi-array cases; tilt angle and distance between arrays increase negative module forces; effects of building depth and parapet height on negative module forces are not obvious; and recommendation values in JIS C 8955 Standard correctly estimate negative mean module force coefficients but not peak values.

View full abstract

In recent years, the large-scale power generations using photovoltaic arrays (Mega solar) are spreading quickly. Although the ground installation type of the Mega solar was main, since the flatland in which large-scale installation of photovoltaic arrays are possible has decreased gradually, it is thought that the installation to a slope will also progress from now on. Then, the wind tunnel experiment using a photovoltaic array model was conducted for the two-dimensional slope, and wind force coefficient which acts on the panel was investigated. Part 1 reports the results about wind velocity distribution around slopes in experiments.

View full abstract

Wind force coefficients for the PV arrays in the sloping ground was measured by the wind tunnel experiment. When an array was installed in a slope, a wind loads are increasing. And the load reduction effect of the windward array may be unable to expect. The increasing wind loads will be covered by the wind force coefficients of JIS C 8955 by using both the angle of the array and the inclination angle of the ground.

View full abstract

Ground effects for the aerodynamic forces on a solar panel were experimentally studied by using 2 dimensional model, in order to clarify their general characteristics. When the angle of attack was small, the observed characteristics were similar to the previous studies that was conducted for airfoils. On the other hand, complicated characteristics were observed when the angle of attack was larger.

View full abstract

There has been an increase in the case to install a fin on the walls of the high-rise building in order to reduce the burden on the indoor air conditioning, energy saving. But it is important to wind load of the fin, has not been studied. In this paper, the characteristics of the peak wind force acting on the fins of the wall building.

View full abstract

This report describes trial of wind load reduction by aperture and fluctuating characteristics of internal pressures. The building is often damaged in the strong wind induced by the tornado or a typhoon. Most of damaged portions are cladding and windowpanes. Moreover, roofs are caused by resultant forces due to increased internal pressures and local negative external pressures. In order to reduce the wind load of a roof, opens are intentionally prepared on the building surface of a wall intentionally. This research examines conditions that make the large wind load of roof subside.

View full abstract