The effects of ground-surface roughness parameters to the power law indices of wind velocity profiles were examined by using LES results. The conventional method based on the roughness density underestimates the power law indices of the velocity profiles over built-up area. With considering the random distributions of building heights, we modified the method with setting an upper limit of the roughness density. The obtained values coincide well with LES results.

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In order to evaluate the reference wind for wind environment assessment, JMA-mesosclale analysys(MANAL) data were considered adaptable. MANAL data were verified and compared with the data of AmeDas and Doppler Lidar wind observations. MANAL data in the air, within the statistical range, showed a generally good response to other wind data.

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In order to evaluate the reference wind for wind environment assessment, JMA-Meso analysis data (JMA-MANAL), SDP wind data and wind observations using Doppler Lidar are compared, was a study of advanced settings. Daily variation due to differences in altitude, but the wind was found, some high wind speed data showed the possibility of wind on the ground will be represented in the statistical range.

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The wind observation data of the meteorological offices are often used as references for local wind conditions. Those observation data can be regarded under the influences of surroundings, such as local topographical conditions or buildings. Present study shows the way for eliminating their influences by using CFD data Then modified annual peak wind velocity data are shown.

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In this study, turbulent flow fields of tornado-like vortices generated by a numerical tornado simulator have been investigated using the LES turbulence model for two typical swirl ratios. A laminar vortex appears for the low swirl ratio case, which shows weak fluctuating velocities near the ground and root mean square (rms) of the fluctuating velocities are several percent of the maximum tangential velocity at the radius in a cyclostrophic balance region. On the other hand, a turbulent vortex occurs for the high swirl ratio case, in which the high fluctuating velocities are observed at the level close to the ground and the maximum value of rms of radial fluctuating velocity exceeds 80% of the maximum tangential velocity.

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Large-eddy simulations (LES) are performed on the reactive air pollutants dispersion in three kinds of urban street canyons that have various roof-heights levels. A line source that emits nitrogen monoxide (NO) is set on the bottom of the canyon space in each case. NO disperses on the cavity eddy and reacts with Ozone included in the free stream. The reaction has a significant influence on the concentration field of a city block scale. However its influence rate changes in different urban configurations, making magnitude relations between concentrations of Ozone, NO and the product are altered in three analysis cases.

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In recent years, the deterioration of the air environment of the city becomes a problem while multistory and making the building in the city high density. One of the problems is a street canyon phenomenon. This is a phenomenon that a waste heat and exhaust gas stagnates to the space (canopy) of the main street between the high-rises buildings. The flow field, the temperature field and the concentration field in street canyon of a pollutant are complicated. The high reliability experimental data is required for an evaluation, a prediction and a countermeasure to each field. Although there is a lot of research which paid its attention only to the flow field, there is no example which paid its attention to the temperature distribution of the flow field on the surface of a street. Therefore, the purpose of this study is making clear experimentally the difference of the temperature distribution in the road surface between the arrangements of the building along a heated street canyon.

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In recent years, there has been considerable research focusing on nonuniformity of building heights in order to improve thermal comfort and air quality of urban area. In some previous studies, it is reported that the cooling potential of upper wind and the momentum transported from upper area to near ground area can improve wind environment at pedestrian level in some extent, however, it is likely to give harmful effects in the leeward area because of the loss of the cooling potential and momentum. Therefore, a study on not only thermal comfort and air quality within building site but also the adequate evaluation of the negative effects on the leeward area is necessary. In this study, LES was applied to the flowfield over four cases of buildings model to investigate the harmful effects quantitatively based on energy dissipation of total kinetic energy by the kinetic energy balance analysis.

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In recent years, there has been considerable research focusing on nonuniformity of building heights in order to improve thermal comfort and air quality of urban area. In some previous studies, it is reported that the cooling potential of upper wind and the momentum transported from upper area to near ground area can improve wind environment at pedestrian level in some extent, however, it is likely to give harmful effects in the leeward area because of the loss of the cooling potential and momentum. Therefore, a study on not only thermal comfort and air quality within building site but also the adequate evaluation of the negative effects on the leeward area is necessary. In this study, LES was applied to the flowfield over four cases of buildings model to investigate the harmful effects quantitatively based on energy dissipation of total kinetic energy by the kinetic energy balance analysis.

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The wind tunnel experiment to measure each terms of transportation equation of concentration variance in vicinity of obstacles were conducted. Inlet flow profile follow 1/4 power law. Measurement area is in between area of blocks which were arrayed to represent urban city geometry. Concentration and velocity were measured in same time history and correlation term was resolved in the space. By calculating the partial difference, the production term of concentration variance were considered. Large value of production in longitudinal component was observed near source and near wall. That of horizontal component shows change of sign near source. Vertical component took large value in boundary face of obstacle height.

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In the case of NBC terrorism attacks or gas leakage accident of a chemical facility in an ur-ban area, there is a possibility that leaked gases give a harmful impact to human body even in very short time exposure. Therefore, it is important to estimate not only the mean value but also the instantaneous value of the hazardous gas concentration. In this study, we advance these numerical techniques to a stage of the gas dispersion problem, and we conduct wind tunnel test as well as LES for the turbulent wind flows and hazardous gas dispersion emitted from the point source in the coastal area of a city. Also, we elucidate the predictive accuracy of LES comparing with the wind tunnel test.

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It is known that residential damage occurs at wind speeds exceeding 30m/s and rises exponentially with the increase of wind speed. On the other hand, it is indicated that the condition of construction, such as the roof form, exterior material, age and construction method of houses, also have an influence on the extent of residential damage. Although, unfortunately there are only a few reports which have quantitatively examined the effects of construction conditions on such damage. This paper offered an approach to an analysis of roof damage through correlation analysis using quantified structural conditions of residential roof based on the questionnaire survey on Typhoon Mireiile (9119). We provided quantitative analysis of qualitative data such as the shape and material of roofs using a quantified method. It was found that the roof shape, and the angles between ridge and wind direction were a significant factor in the extent of damage to roofs.

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The characteristics of tornados and tornado disasters are strongly dependent on the locality. Recently, tornado disasters often occur in Hokkaido and Tohoku Districts. We constructed a database of tornado disasters in these two districts after 1949. The database consists of a lot of information on tornados, including the newspaper articles. The present paper shows the characteristics of the tornado disasters obtained from an analysis using the database.

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Tornado disasters have often occurred recently in Japan. Strong winds caused damage to humans, buildings, lifelines and others. The authors carried out hearing surveys at three municipalities that were subjected to tornado disasters recently and investigated the responses of the local governments after the disasters. The results provide useful information for making the management manuals to be used by local governments during and after tornado disasters.

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This study improved the forecast of mean and fluctuating wind speed by considering the forecast error. Also, by identifying the peak factor by least square method with forgetting factor, the forecast of maximum gust was improved.

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The trajectories of simple shaped debris released in a tornado-like vortex was investigated numericaly. The trajectories with variety of three vorticies and two dibris were examined. The characteristics of maximum horizontal speed of flying debris were discussed.

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An impact test device using a roof tile as a missile was developed. The performance of the device was examined. The impact test using laminated glasses as a test specimens was carried out. The impact resistent characteristics of laminated glasses against a roof tile was clarified.

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Conical vortex formed on a upper surface of a cube in a smooth flow has been investigated by a 3 dimensional PIV system. According to the analysis of the PIV data sampled every 500Hz, the strength of the conical vortex at the one side is always greater than that at the other side. The pair of the conical vortex sways in a body. The stronger conical vortex at the one side goes down just after the cube, and then the strong down flow goes around the vortex.

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This paper proposes a method of motion-induced wind forces derived from using Kramers-Kronig relation. The validity of the method is indicated by comparing the results deduced from the proposed motion-induced wind forces with test results obtained from a wind tunnel test using an elastic model.

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This paper describes an analysis of proper orthogonal decomposition, which is refereed as POD, for wind pressure field acting on a square prism in three-dimensional flow under the aerodynamic vibration. In the simulation of aerodynamic vibration, the Improved hybrid aerodynamic vibration technique is applied. From the result of POD analysis, the positive symmetry mode and reverse-symmetry mode can be shown as a typical mode of POD.

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In this paper, the analysis is conducted more to aim at the reverse-symmetric mode which is shown in the part 1 of these papers. A reverse-symmetric mode and Variation Coefficient of Overturning Moment for the normalized wind velocity show a similar tendency, and this tendency vouches a physical effect to increase the response from the contribution rate. Furthermore, the motion-induced Wind Force Coefficient is defined, and the coefficient of wind force has agreement with Motion-induced Wind Force Coefficient of a reverse-symmetric mode in the resonance area especially.

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In this paper, the wind force coefficient at each story is evaluated and the characteristics of wind pressure fluctuation are discussed. The two types of phase distribution are shown. The distributions can be distinguished from the case of vortex shedding and the case of galloping vibration. It can be imagined that conical vortex generates from the phase distribution of vortex shedding.

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In the prediction of gust response, the spatial correlation of fluctuating pressures is one of the most important parameters. 2D, that is to say, span-wise and chord-wise, gust forces are evaluated by integrating differential fluctuating pressure between on the upper and lower side in chord-wise. If we suggest an approximate function of 2D coherence at each point of the surface, we define a more general transfer function on the field of frequency, and then evaluation of gust response may be more precise. Then, in this research, we considered characteristics of the spatial correlation of fluctuating pressure acting on various rectangular cylinders with characteristics of approaching flow, width of the cross-section and the depth-to-height ratio changed. Finally, then, we proposed a model 2D coherence function of differential fluctuating pressure, which can be applied to more universal rectangular cylinders.

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The effects of optional structures with shape change along longitudinal axis on wind load of rectangular cylinders with side ratio 3 were studied experimentally in a wind tunnel. The present Strouhal number and drag coefficient of rectangular cylinder without optional structures agreed well with existing results. Drag coefficient increased while coefficient of fluctuating lift decreased significantly with optional structures. Peak frequency became one third, which indicated transition from reattachment-type of flow to perfect separation type. It was observed that 2 peak values in spectrum of lift force for optional structures with shape change longitudinal axis were smaller than other cases.

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When we perform numerical flow simulation of drag force exerted on a square cylinder under rapidly accelerated flow, as a usual combination of the boundary conditions, we specify flow velocity on the upstream boundary and the traction free condition on the downstream boundary. However, this combination results in a streamwise pressure gradient over the computational domain. In order to investigate the effect of this pressure gradient on the computed unsteady drag, we perform a series of simulation where the square cylinder is moving in a still fluid by using the ALE method. From these computations, the unsteady drag in a flat overall pressure field is obtained. As a result, the peak value of the computed unsteady drags reduced about 30% for non-dimensional rise time 1 and about 10% for non-dimensional rise time 10.

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Some members of a transmission tower, which is constructed by steel pipe or angle having a big slenderness ratio and a small initial stress, may cause a local vibration due to a vortex-induced oscillation or an overall tower vibration. A type of truss frame brings about an ovaling vibration as a local vibration, which is an out-of-plane vibration of horizontal members of the tower body. Such local vibrations may cause connection-bolt loosening and/or fatigue problems of welded parts. This paper discusses a vibration control procedure of the local member, which utilizes High Damping Rubber (HDR) to increase the damping of each frame member. Some results of free vibration analyses and dynamic response analyses using one panel of an actual transmission tower in which some ovaling vibrations were recognized during typhoon MAEMI in 2003 indicated the high performance for vibration control of the local member.

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The wind response changes when a multistory building is adjacent. In this study, The responsive condition when the building neighboring is clarified. The influence that the interval gave the wind response was examined.

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In order to investigate fundamental characteristics of flow and aerodynamic forces of neighboring high-rise buildings, LES computation is applied to the flow around two square cylinders in uniform flow.

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Recently, cable-stayed bridges get larger and longer. As a result of this, aerodynamic instability of stay-cables becomes obvious. For instance, dry-state galloping, rain induced vibration, flutter and so on. It is pointed out that dry-state galloping in stay-cables is caused by the suppression of Karman vortex. But the mechanism of it is not clarified yet. For that reason we must examine it in detail. It is known that end conditions of the inclined cable model have great influence on the results of the experimentation in wind tunnel. Therefore, in this study, we adopt the cable model which can measure the aerodynamic forces partially in order not to be influenced by the end conditions. We consider the occurrence of dry-state galloping in stay-cables by using the cable models which have various kinds of surface configuration in order to suppression of Karman vortex.

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Wind tunnel experiments were conducted on wind-induced vibration of a inclined cylinder model up to over 50m/s in smooth and turbulent flow. Response amplitudes were presented with drag coefficients that were obtained in a simple method. The order of the onset wind speed of the responses corresponded to critical Reynolds number for only 30 degree skew angle case. The response was generally suppressed in turbulent flow, but large response with strong excitation occurred for 30 degree skew angle with Iu=4.6% turbulence.

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Dry galloping characteristics of an indented surface treatment cable were experimentally investigated in smooth and turbulent flows. Design criteria for dry galloping of an indented cable were in good agreement with those by FHWA, UAS. In addition, it was confirmed that dry galloping is stabilized by wind flow turbulence.

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This paper presents an analysis of Hakucho Susupention Bridge tower and girder vibration with the main focus on relationship between vibration amplitude and wind velocity. Main finding is the tower in-plane vibration under moderate wind velocity between 14 to 24 m/s, where the downstream leg of the 132m tower oscillates on its strong axis. The along-wind oscillation is characterized by a single-frequency harmonic-like response that resembles the in-line vortex shedding response. Influence of the tower in-plane vibration is also observed on the girder, where larger girder lateral vibrations were measured within the same range of wind velocity.

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Wind pressure on high-rise building in urban area was predicted by homemade Large-Eddy-Simulation code. The prediction accuracy of the square cylinder, were assessed by comparing their results with those obtained by wind tunnel test. The results of LES showed good agreement with experimental data.

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It is important to need to estimate the response of building against wind force in elasto-plastic range because the tall building has yielding component such as steel damper. Wind response evaluation using time-history analysis is based on a Monte-Carlo method of stationary random process, the response should be processed as a number of statistics. As wind response estimation method, previous studies are discussed about a influence of wind force dispersion on response and energy input for simulated wind force created by the triangular series model, but these have not been fully comprehended yet. In order to evaluate the reliable wind response, it is need to use wind tunnel experiments result whose distribution of spatial correlation is closer to natural wind compared with the simulated wind force. In this paper, the characteristic of modal wind forces obtained from wind tunnel experiments are evaluated.

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Time history analysis are carried out by using the wind force obtained from wind tunnel test data. Objectives of this paper are to elucidate the influence of the wind force dispersion on response and to show the basic data. As comparing with the 1-wave ensemble estimation case, the dispersion of response by using the 5-wave ensemble average becomes half. The dispersion of response is not influenced by the difference of the building aspect ratio, mode shape. However, the dispersion of response decreases when the building have high damping ratio.

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The most of the damages due to the strong wind in the past occurred on the cladding. There are so many studies about the pressure characteristics acting on the cladding. However, at least inside Japan, the number of studies to verify the strength or damage mechanisms of cladding or ceiling is few. Moreover, when the wind loads are considered, we should think about the fatigue characteristics of cladding against repeated loading. In this study, the basic characteristics of the open topped pressure chamber for testing wind-resistant performance of cladding/components are verified. After that, using the actual ceiling, the strength and the collapse procedure of ceiling board system is examined.

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In the wind resistant design of the building, it is designed so that the member stress by the highest response at the strong wind may become below the permissible stress. For instance, the damping components (eg. lead and ultra low yield stress steel, etc.) used by the base isolation structure might be destroyed by the energy absorption or the fatigue damage. Not only the maximum stress but also it is necessary to evaluate accumulated load to showing these safetys. However, the evaluation method is not shown in a present practical standard or recommendations. In the present study, to evaluate accumulated load effects of the wind acts on the building, the influence of the effect of accumulated the alternating load that one strong wind event gives the structure is examined. A total energy input and the accumulation fatigue damage are targeted. The equivalent time that becomes equivalent to the case for the maximum wind speed of the strong wind event to continue constantly is proposed.

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A light gauge metal sheet roofing was tested by the pressuring method, which use a time series of fluctuating pressure acting on the cladding of a low building during a model typhoon. The test method can allow the estimation of the realistic fatigue damage of any specimens, because it was the realistic wind loading fluctuations. A few problems remain to obtain the rational and realistic test method for the fatigue assessment of building cladding.

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To request the design wind loads for the components and claddings by the wind tunnel experiment, it is important to evaluate the spacing averaged wind pressure. However, it is not examined to slender rectangle tributary are like the folded-plate roof. The tributary area is growing by the same width of finding. Then, the evaluation method of the peak value for such a long and slender material is proposed. The evaluation method of using the model of a simple beam leads the peak wind pressure coefficient based on the response of the material. The usual averaging method undervalues the peak coefficients, it was necessary to divide the peak coefficients.

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Aerodynamic coefficients for a jib crane model consist of circular cylinders were measured in a uniform flow. The horizontal wind load of the out-of-service crane is larger than that of the in-service crane, but the overturning moment of the in-service crane may be larger than that of the out-of-service crane because of their presentations. The wind loads of the in-service jib crane at a high pitch angle clearly dominate the wind design for the crane.

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This paper investigated the properties of unsteady wind force on an elliptic cylinder under a rapid change from steady flow. In this study, a short-rise-time gust from steady flow was generated by the control of blade rows which were installed for generating a pulsation flow. As a result, we confirmed that the overshoot phenomenon of wind force occurred under a rapid change from steady flow as well as from calm. And it was found that the overshoot coefficient, defined by the ratio of maximum to a steady-state value of wind force, decreased with an increase in the ratio of the initial wind velocity to the target wind velocity. the overshoot coefficient which was classified with the ratio of wind velocity was determined by a redefined non-dimensional rise time which was composed of a rise time, the body size, the initial and target wind velocity.

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Wind loads on components and cladding of buildings varies depending on the building shape, wind direction, the position of the components and cladding, and so on. For regular shaped buildings with a rectangular plan, local design pressures and their trivial areas and positions are specified in the provisions of many regulations and codes. This paper discusses wind tunnel results of local peak pressures acting on stepped roofs and walls of buildings featuring a setback. The local pressures acting on the periphery of the roofs and walls were found to be larger than the design values specified for regular shaped buildings in the AIJ recommendations.

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This paper describes the reduction effect of peak wind forces acting on photovoltaic arrays which are located on the ground. The wind force reduction coefficients were investigated using wind tunnel tests. The tilt angle of the arrays was 30 degrees. The test parameter was the placement of the arrays. As a result, the reduction coefficients of the positive wind force acting on arrays of the most south side were bigger than those of the north side with the influence of the tilt direction of the array. Furthermore, the reduction coefficients of the negative wind force acting on arrays of the most north side were bigger than those of the south side.

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To investigate the peak wind pressure acting on the soffit of the piloti, the wind pressure experiments were conducted for various types of building height or piloti height. As the results, the negative peak pressure coefficient was almost -5 regardless the building height or piloti height.

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Recently, the case where the steel pipe concrete compound structure is used increases in the construction of the structure. In such a steel pipe concrete compound structure, the column group that consists of two or more columns is formed, and they are exposed to the wind for a long term while it is constructing it. Moreover, there are a lot of one to have the structure that two or more cylinders are adjacent in the exhaust cylinder of the nuclear plant. Those wind-resistant stabilities are important examination problems. In the present study, We examined that aerodynamic characteristics of five cylinders in proximity under wind velocity increase in short time duration by measuring the transition air power, measuring the transition surface pressure, and making the flowfield around the section visible.

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The aerodynamic characteristics of multiple arranged photovoltaic arrays are investigated in terms of inflow turbulence by wind tunnel test. Conical vortices are strongly generated only in the smooth flow when wind direction is inclined by 30 degrees with the North. Conical vortices cause low pressure area on upper surfaces of photovoltaic arrays, then wind pressure coefficient comes up by comparison with in the turbulent flow.

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In late years, the environmental problems such as the global warming, are leading attraction to photovoltaic power generation. There are many cases of photovoltaic power generation, installed on detached houses, but there had been few cases of its installation on apartment. However, recent trend such as decrease of installation cost and increase of generation efficiency are accelerating the installation of photovoltaic generation on apartment. Although, there are some reports on wind load at solar panels, there are few reports on experiment assuming installation on apartment. This study, aimed to clarifying the wind pressure which acted on rooftop solar panels installed on apartment, and experiments were conducted a boundary layer wind tunnel.

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Performance of a cross-flow wind turbine located above windbreak and snow fences and the associated velocity fields have been investigated experimentally. Effects of the covered area of the porous fence, as well as the direction of the turbine rotation were examined. The standard porous board fence model had the geometric shielding rate of 60%. When the turbine was rotating clockwise, i.e. the blades on the upstream side of the turbine were moving upward, the maximum power coefficient increased with the increasing the covered area of the porous fence. In contrast, when the turbine was rotating counterclockwise and the small clearance between the turbine and the fence, the maximum power coefficient decreased rapidly with the increasing the covered upper area of the fence. It was found that the power of wind turbine was related to the flow velocity in the clearance region and the rotational direction of the wind turbine.

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For the purpose of practical application to a mid-size wind turbine, we have developed a very compact rimmed diffuser (wind-lens structure). Using this compact rimmed diffuser, we have achieved a two-to-three-fold increase in output power as compared to conventional (bare) wind turbines, due to concentration of the wind energy. We are now developing a wind-lens turbine of 100 kW at a rated wind speed of 12 m/s. The rotor diameter is 12.8 m, which is much smaller than that of a conventinal wind turbine with the same rated power, say, two-thirds the rotor size.

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In the present numerical study, we carried out the large-eddy simulation (LES) of the wake generated behind the wind turbine generator under optimal tip speed ratio. Particular emphasis was placed on the effect of inflow turbulence on the wake region generated behind the wind turbine generator. Through comparisons between three cases with and without inflow turbulence, the speed loss of about 30-40 percent existed in the wake region (1D-5D) in all the cases, where D is a diameter of a rotor.

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