The possibility of the application of the mass-consistent flow simulation model (MASCON model) to the evaluation of the topographical effects on the design-wind speed for the wind-resisting design is investigated. This is because a simple and efficient method is required for that purpose due to the reason that it is difficult to determine the design-wind speed, which includes the topographical effects, for the sites away from the meteorological observatories based solely on the AIJ Recommendation. Through the numerical experiments with a meso-scale meteorological model on the thermally stratified air flows over an isolated hill, it is shown that, for the strong wind, say 40m/s, horizontal distribution of the near surface wind speed becomes similar to the one with the neutral stratification. This suggests the possibility of using the MASCON model for the evaluation of the topographical deformation of the wind field. A comparison between the simulations with the MASCON model and the meso-scale model for the realistic topography is also presented.

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A mixed probability distribution function (MPDF) was proposed for typhoon simulation, which is applicable to any locations by changing a weighted parameter. A modified orthogonal decomposition (MOD) was also proposed to simultaneously reproduce probability-distributions of typhoon parameters and their correlations. The annual maximum wind speeds at the five typical sites in Japan simulated with the proposed methods showed favorable agreements with the observations, while the conventional methods overestimated those for the long-term return period.

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The purpose of this study is to elucidate the wind field at the time of fine weather in Kanto Plain. We have observed the wind profile in the surface boundary layer using Doppler Sodar. It is located in the Tokyo bay coast since August, 2003. When the migratory anticyclone covered Japan, and the temperature difference in the daytime and nighttime was remarkable, two types of wind profile, sea breeze, land breeze was measured. And, these wind profiles showed daily variation. During the transition from the land breeze to the sea breeze, the wind direction changed from northerly to southerly. And during the transition from the sea breeze to the land breeze, the wind direction changed from southerly to northerly. In this paper, the relationship between sea breeze and land breeze is discussed.

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A rotating track was observed for Typhoon Fung-Wong (T0211) during its passage around the Okinawa Islands on 24-26 July 2002. We analyzed this phenomenon by using satellite data and surface meteorological data from the viewpoint of its interaction with Typhoon Fengshen (T0209). This mutual interaction, appeared as cyclonic orbit influenced by the other typhoon, occurred when the center of two typhoons approached within around 1000km. Assuming that these binary typhoons are expressed by two isolated vortices with positive vorticities, we performed numerical experiments about their interaction. The result indicated that the behavior of two unequal vortices with same size but different core vorticities was similar to the observed feature of Typhoon Fengshen (T0209) and Typhoon Fung-Wong (T0211). It is quite likely that the interaction of two unequal binary vortices with large separation distance caused the rotating trajectory of Typhoon Fung-Wong (T0211).

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Generation mechanism of a strong local wind “Karak-kaze” in the Kanto Plain is studied by using hourly meteorological observations at 75 AMeDAS stations and twice-daily upper air observations at Tateno for the years 1992 – 2001. It has been shown that the local wind blows in wintertime under typical synoptic conditions of strong east-west pressure gradient associated with strong northwesterly winds at upper layers. The local wind shows a very clear diurnal variation with the maximum speed in the early afternoon of sunny days. It has been suggested from vertical profiles of air temperature that strong surface winds are associated with thermal convections in the daytime. In general the strong winds start at about 09 JST and calm down at about 18 JST simultaneously all over the Kanto Plain. Consequently, it has been concluded that the local wind “Karak-kaze” in the Kanto Plain is generated by lowering strong winds from the upper layers to the surface layer by thermal convection in the daytime.

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The paper reports the feature of an annual average and daily fluctuations of wind speeds in Kyushu area for wind power energy development. Our survey based on NeWMeK data of 122 locations from 1999 to 2003 indicates that annual mean wind speeds are strong in northern Kyushu and monthly mean wind speeds are higher in winter than summer. There are a few observation points which have annual average wind speeds of over 4 m/s at a height of 30m through a year. Since it is difficult to present the overall characteristics of wind fluctuation in Kyushu, several representative observation points are selected for minutely investigating the fluctuation of wind speed and direction. Though the locations having the higher daily mean wind speeds have mostly the smaller daily mean of the wind fluctuations, several locations have the large intensity of turbulence even in a high wind speed. Most of locations have shown the different intensities of wind fluctuation.

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In the present study, the numerical simulation of airflow around a steep cape was performed by using the mesoscale model CSU-RAMS (Colorado State University, Regional Atmospheric Modeling System) and the CFD (Computational Fluid Dynamics) model RIAM-COMPACT (Research Institute for Applied Mechanics, Kyushu University, Computational Prediction of Airflow over Complex Terrain). The wind speed obtained by the CSU-RAMS was in a good agreement with the observed data. On the other hand, the numerical results obtained by the RIAM-COMPACT demonstrated that the changes induced on the wind field by the topographic effect, such as the flow impingement, separation and reattachment, are successfully simulated. If the CSU-RAMS and the RIAM-COMPACT can be merged effectively, it can be said that a highly precise numerical simulation will become possible.

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A numerical model using unsteady Reynolds-Averaged Navier-Stokes equation (URANS) to predict local wind deformation of correlated wind fields affected by bottom geometry and turbulence boundary layer has been developed. A frequency filter of correlated wind field for URANS model to separate different scale variations has been investigated. The characteristics and validity of the URANS model under the unsteady wind condition are discussed for the cases of a flat bottom and a realistic geometrical condition. Sensitivity of mean wind profile and turbulent kinetic energy to the random wind conditions are discussed. It is found that URANS gives more realistic turbulence intensity profile rather than the conventional RANS model.

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We are developing MEASURES, Multiple Radiological Emergency Assistance System for Urgent Response, which can identify the nature of nuclear accident and predict its course and the environmental consequences. RAMS, the Regional Atmospheric Modeling System, is used for forecasting meteorological phenomena in MEASURES. We have added 2 functions to RAMS in order to apply RAMS to micro scale region. One is a new scheme to simulate a flow around a building. The momentum equations are modified to approximate the effect of building with air drag force. The second function is a new closure model developed by Castelli. We simulated a flow over a 3 dimensional hill, and it is found that the new model can be useful for a micro scale region. After running RAMS, HYPACT, Hybrid Particle and Concentration Transport Model, is used in MEASURES. It simulates dispersion of gas that is emitted from nuclear power plants. An example of gas dispersion over a 3 dimensional hill is shown in this paper. And we have assessed the accuracy of RAMS by comparison with field observation data around Mt. Tsukuba, located in the north of Tokyo. The computed results of wind speed and wind direction showed good agreement with field observation data.

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In this research, we provide the numerical model by using Lund's method for spatially-developing thermally stratified turbulent boundary layers. In order to generate the inflow turbulence, the turbulence parameters for velocities at recycle station are rescaled and introduced to the inlet boundary,while temperature is treated as a passive scalar. The generated inflow data for temperature as well as velocities are introduced into the main computational domain, where temperature is solved taking into consideration buoyancy effects. With this method, a long fetch is not necessary to simulate the spatially-developing boundary layer. We carry out LES analysis of the spatially-developing thermally stratified boundary layers. We investigate the turbulence structure inside turbulent boundary layers under both of unstable and stable conditions.

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The demand of numerical prediction of wind flow over rough surfaces such as urban areas is increasing. Reproduction of the roughness configuration in the mesh discretization is a direct way for numerical calculations. However, the roughnesses near the ground such as buildings or houses are complicated. Therefore the reproduction increases the computational load and can cost a lot of time and money. In order to reduce this, we applied a filtering operation, that is an averaging in a space containing solid obstacles, to the Navier-Stokes equations and derived filtered equations with a subgrid scale turbulent modeling for the Large Eddy Simulation. Consequently, we can take the obstacles to be porous media distributed uniformly in the mesh. The configuration of the obstacles does not need to be reproduced any further. We can calculate the space-averaged property of flows with coarse meshes and a reduced computational load. We present some calculations of turbulent boundary layer over a rough surface. The performance and effectiveness of the calculation method are examined by comparing with the measured data by wind tunnel experiments.

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A numerical model for turbulent canopy flow has been formulated applying the LES concept on flows both above and within canopy. A fundamental equation together with numerical solution method of the large amplitude oscillation of an elastic beam which simulates an element of canopy layer, a stalk of grass, are presented. In the developing stage of turbulence, the inflectional point instability mechanism of shear layer acts to generate two-dimensional spanwise vortices, which then deferm into three- dimensional pairs of longitudinal vortex structure.

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The canopy model for reproducing the aerodynamic effects of trees was optimized for the CFD prediction of wind environment at pedestrian level. The canopy model adopted in this research uses the revised k-ε model using a “mixed ” time scale concept as a base with extra terms added into the transport equations. After reviewing the previous researches on modelling of these terms, two types of canopy models were selected. Then, the model coefficients included in the extra term added to the transport equation of ε were optimized by comparing numerical results with field measurements of wind velocity and turbulent energy k behind pine trees.

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Complex heat transfer fluxes occur between external surfaces of building walls and the urban canopy layer on typical summer days. The convective heat transfer coefficient on urban surfaces is an essential index that indicates roughly the characteristics of sensible heat fluxes inside the canopy layer. An experiment was conducted to obtain a formula for predicting convective heat transfer coefficients. The radiative heat transfer was calculated by Gebhart's absorption factor method. The heat transfer coefficients over a rough floor in the velocity range from 0.5 m/s to 2.0 m/s were larger than those over a smooth floor. An experimental formula for the heat transfer coefficients with a function of reference velocity and bulk Richardson number was derived by a nonlinear regression model. Experiments must be carried out to accumulate data and obtain high quality prediction formulas.

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The flow field in the passage between two buildings is simulated using a two-layer k-ε model and the results are compared with the wind tunnel data. This study concentrates on the variations of the mean wind speeds within the passage under different wind directions (0°, 15°, 30°, 45°, 60°, 90°) and the influence of the height difference between the two buildings is also investigated. Good agreement is obtained when the two buildings is of the same height. Although the agreement is less satisfactory when there is a height difference between the two buildings, the general trend of the wind velocity variations within the passage is similar to that of the experiment. The salient flow features can still be depicted by this economical approach and it is considered adequate at the stages of preliminary design.

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The outdoor wind environment has various problems in both summer and winter respectively. It is affected by various weather factors such as wind, air temperature,humidity and radiation etc. In order to improve the inferior outdoors thermal environment in summer, improvement of ventilation is considered as a major factor among various factors. On the other hand, increasing wind velocity in winter is considered significant factor of human's unpleasantness. This research aims at development of the optimum design method for pleasant outdoor thermal environment in the apartment block in both summer and winter. In this paper, three cases are examined: (1) two cases (case1 and case2) which are different design objective (improve the ventilation in summer and control of the cold wind inflow in winter) are examined using GA (Genetic Algorithm), (2) in addition, as a multi-objective optimization, the case (case3) which both improves the ventilation in summer and controls of the cold wind inflow in winter is examined using MOGA (Multi-Objective Genetic Algorithm).

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Ventilation efficiency around heavy traffic road covered with elevated highway and side buildings is evaluated with Visitation Frequency (the times for contaminant to return back to the objective domain) and Purging Flow Rate (the air flow rate for defining the domain averaged concentration). These are analyzed by the CFD (Computational Fluid Dynamics) based on the standard k-ε model. The properties of VF and PFR of four objective domains are analyzed with the changes of wind direction and arrangements of road center obstacles under the elevated highway. The resulting VF more than 1.0 are shown for all cases, which means that contaminant circulates within the objective domain enclosed with the elevated highway and side buildings. The influence of the arrangement of the buildings around the objective domain and the structure in the domain on VF is large. In the case of no obstacles under the elevated highway, the ventilation frequency tends to be high.

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The effects of roadside trees on flow and diffusion fields within the street canyons in the central part of Sendai city were numerically investigated by CFD analyses coupled with calculations of radiation and conduction. Several cases of analyses were carried out to clarify the effects of arrangements and density of trees, and shapes and elevations of tree crowns. The situation where trees were not planted was also simulated for comparison. In the case without trees, a large recirculation was formed in the street canyon and the air heated by high temperature road surface and contaminated by exhaust gas from automobiles was advected to the area above the sidewalk. This large recirculation did not appear in all cases with roadside trees due to the windbreak effects of trees and the regions with high temperature and high concentration were formed only near the surface of the roads.

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The purpose of this study is to clarify the regional characteristics of heat balance in urban space inside Sendai city. CFD analyses of mesoscale climate in and around Sendai city were carried out. Regional characteristics of heat balance in urban space were examined based on the CFD results. Special attention was paid to the contribution of sea breeze to the heat balance in urban space. Effects of urban tree planting and high-albedo surfacing were also examined. It was confirmed that the effects of sea breeze are very large in the coastal area. Inside the urbanized area, the effects of tree planting and high-albedo surfacing are relatively large, in particular, in western part of the urbanized area. But the effects of sea breeze is more important than those of tree planting and high-albedo surfacing in the eastern part. The mechanism that causes these differences was discussed by comparing the heat budgets in the four sub-domains set inside the urbanized area.

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Nowadays, it becomes to be very important to estimate the CO2 amount that vegetation absorb, concerning to the global warming. In this research, we carry out Large Eddy Simulation analysis to investigate the vegetation effect on the wind field. We expect to express the vegetation effect on turbulence by advancing Feedback Forcing method proposed by Goldstein. As the result, we could reproduce some characteristics of vegetation, isotropic and dissipation within vegetation, large momentum exchange on interface between atmosphere and vegetation, and so on. And we apply this method to real urban area.

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CFD analysis of airflow and temperature in Tokyo area of 25 square kilometers, which includes a large river and a lot of buildings, was performed. To deal with these buildings, the horizontal mesh resolution was set as 5 meter, and highly parallel vector super computer system was used. The result showed that, the airflows from the large river and sea cooled the temperature of the surrounding areas.On the other hand, in densely built-up areas, the airflow became weak, and the temprature increased.

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Even inside urban areas, hazardous materials are often produced and stored, there is a possibility that the accidental spillage occurs for the transportation and storage of the materials. Therefore, we carry out large-eddy simulation for plume dispersion in actual urban area and investigate dispersion process of a plume and occurrence of peak concentrations based on various kinds of surface roughness in the urban canopy for safety analysis.

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This study investigates the spatial distribution of turbulent time scale around a bluff body used in revised k-ε models. The turbulent time scale for obtaining correct values of Reynolds stresses from the linear eddy viscosity modeling was evaluated by using LES data and its spatial distribution around a cube was compared with the time scales given from the models based on a mixed time scale concept, i.e. S,Ω and S-Ω models, proposed by Nagano et al.

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Hydrogen energy attracts attention as eco-friendly energy recently. Especially the fuel cell vehicle that uses hydrogen as fuel will be expected as a post gasoline car in the future. However, since hydrogen gas can burn in mixtures with air from very lean to rich, when hydrogen gas leaked from hydrogen refueling station, the danger of causing explosion is high. Therefore, it is necessary to design so that the serious damage for the windowpane and a human body may not be given in case of emergency accident. So, it is important to predict the blast pressure correctly at the time of explosion. But, an explosion experiment has some problems of a site, time, and cost, so that the numerical simulation is needed for highly precise prediction. In this study, we simulate the hydrogen explosion experiment conducted in the past and verify the prediction accuracy.

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In this study, offshore wind power potential in the supply area of Tokyo Electric Power Company (TEPCO) was investigated by using mesoscale model and geographical information system (GIS). Following results were obtained. 1) The mesoscale model can predict the annual mean wind speed with the error of 4.8%. 2) As Choshi is located at the tip of a cape, annual mean wind speed at 10km offing exceeds 7.5m/s offshore Choshi, while it is only 5.7m/s at northern site. 3) Considering the area 50km from the shore, total theoretical potential reaches 277TWh/year accounting for 94% of the annual demand for TEPCO. 4) Imposing economical and social restrictions, the available potential becomes 94TWh/year, 99.6% of which is exploited by floating foundation. 5) Floating foundation should be developed so that it will fit the water depth between 20m and 200m. 6) When service life of the foundation is set to more than 50 years, the offshore wind farm in this region will be profitable.

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The field test of a small size wind turbine system has been performed in Kanagi, Aomori Pref. The wind characteristics, such as wind speed, wind direction, air temperature and output power of the wind turbine system have been recorded every ten minutes over three years. By the recorded wind characteristics and output power it was clarified that the both of mean wind speed and total output power in a month show large values in winter and small ones in summer. And it was found that the mean wind speed was around 3.2m/s at 2.5m above the ground and the utilization rate was 14 - 16% even in winter. Thus, the wind speed is not enough for the wind power generation by the small type of wind turbine system. So, it is seemed that the equipment to increase the entering wind speed to the wind turbine should be used together. On the other hand, the wind direction was limited throughout the year, and it is suitable for the wind power generation. The noise level from the wind turbine was around 50dB.

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Our aim is to get basic data to increase the efficiency of micro horizontal axis wind turbine (HAWT) systems. The experiments were carried out in an open type wind tunnel and on field. We measured the turbine performance of five-bladed wind turbines with Clark Y, MEL002 and MEL081 airfoil crosssections. Flow characteristics of rotating blades of the turbine were observed using the oil-film and tuft visualization technique. Flow visualization allowed the identification of laminar flow, laminar separation bubble formation, flow reattachment, turbulent boundary layer, and turbulent separation. The complex patterns on the rotating blade surface were confirmed and identified by the oil-film visualization method. The performance of the wind turbine with MEL081 airfoil section was better than the other airfoil sections at low wind speed. It was found that the performance of wind turbine with trip-tapes, which were employed for control of the blade boundary layer, improved at low wind speed.

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Turbulence characteristics in the wake of a wind turbine, especially the behavior in the near-wake region, have been investigated with a wind tunnel. Time-series of instantaneous 2-component velocities were measured by using a x-type hot wire, and the turbulence statistics were examined in detail. The changes in statistics with the distance from a wind turbine show that the an-isotropic turbulence transforms into isotropic one with the development of flow field. Such a transition behavior strongly depends on the inlet flow, i.e., the disturbances involved in free-stream promote the transition of a wake flow. In addition, it is also found that the characteristics of the wind turbine model used in the experiment greatly effect the turbulence behavior in the near-wake region.

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In this paper we describe the characteristics of wind forces acting on a propeller-type wind turbine with three blades. The wind forces were investigated using wind tunnel tests. The test parameters were wind tunnel flow (uniform flow and uniform turbulent flow), pitch angle of the blades, stationary blade positions and tip speed ratio. The following results were obtained. First, the mean drag coefficients acting on the stationary wind turbine at a position where one blade corresponded to a tower were differed from those at the other blade positions. Next, the mean drag coefficients (thrust coefficients) acting on a rotating wind turbine increased as the tip speed ratio increased, and as the pitch angle decreased. The mean drag coefficients in the uniform turbulent flow were larger than those in uniform flow. Finally, the local rms lateral force coefficients acting on the local height of the wind turbine tower increased at the tip speed ratio of 3. The cause is regarded by the frequency of vortex shedding corresponded to the blade-passing frequency.

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A hybrid energy generating system that can use both solar energy and wind energy is proposed. The outlook of this system is like a flower having several pedals. In sunny days, it opens and assembles solar energy by the mirror surface of panels, while in cloudy and windy days it closes and rotates to transfer wind power into electric power. The performances of two different prototypes (Type A and Type B) as electric generator are examined by wind tunnel tests. Type A is composed of six panels (50cm×10cm). Type B is composed of twelve panels (50cm×12cm) with six of them located inside and the other six located outside. The surfaces of the panels have parabolic shape to focus solar radiation at one point. The parameters of the wind tunnel tests are wind speed (3m/s∼20m/s), panel angle (15°∼83°), measured from base line on rotating circle and inclined angle of rotating axis (-30°∼ +30°). As experimental results of Type A, the number of revolutions per minute (RPM) increases proportional by to the square of the wind velocity and Type B, RPM increases linearly by to the wind velocity. The maximum RPM are obtained at the case of panel angle = 60°for Type A, outside panels angle = 60°and inside panels angle = 30°for Type B, respectively. The maximum electric power is 80W in the case of 15m/s for Type B. RPM decreases by about 10% when the inclined angle is in the range of -30°, +30°.

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When Typhoon Maemi passed over the Miyako Island, maximum instantaneous wind speed 74.1 m/s and minimum atmospheric pressure 912 hPa were observed at Miyakojima Local Meteorological Observatory on September 11, 2003. In connection with this high wind, the serious wind damage occurred on the Miyako Island since the 3rd Miyakojima Typhoon in 1968. We already reported on the meteorological situation and the high wind damage in Miyako Islands in some reports. As a result of investigating about the high wind of Typhoon Maemi using meteorological data, such as weather survey data in weather government offices and a weather radar echo charts, it turns out that the high wind were observed under the strong rain band on the west of the ring inside the double eye of the typhoon in this paper. We also classify the damage situation of buildings and structures and compare wind speed records observed at Miyakojima Local Meteorological Observatory with wind loads in Japan Building Code.

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The weather has a great influence on the construction work, and the construction accidents sometimes happened due to the bad weather, e.g. strong wind. Therefore, wind-induced structural accidents during construction were investigated on the basis of the yearbooks of the Japan Construction Safety and Health Association, and it was found that the death accidents happened mostly by the falling dawn of the workers. Therefore, to prevent these accidents, experiments to the subjects were performed on the risk of the assembling and dismantling work of the scaffolds under strong wind. 10 construction workers were joined in the experiments, and the assembling and dismantling work were carried out in the wind tunnel under strong wind. From the results obtained, it was found that there was a high risk in the assembling and dismantling work of the scaffolds even under 10 m/s at the mean wind speed, which was the standard of the work stopping by the law of the Labor Safety and Sanitation.

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It is known that the spread of structural damage is more strongly affected by gust speeds than by maximum wind speeds. The authors have focused on the duration and fluctuation of wind gusts. The results of damage analysis based on the effects of Typhoon Bart in 1999 have indicated that the spread of damage has a higher correlation to the standard deviation of the wind gusts rather than to the intensity of turbulence. Comparisons of the time evolutions of wind records at selected observation points have indicated more serious damage at areas with higher fluctuations of wind speed. Although the above investigation is based on a survey of the damage of only one typhoon, it is suggested that fluctuation intensity as well as the duration of high wind speed is a significant factor in the spread of structural damage.

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Wind direction changes all the time in natural winds. Although many results of field measurements have pointed out that that wind pressures on claddings have been influenced by the change of wind direction, there are a number of unclarified points about it. That is reason why the change of wind direction in natural wind has non-stationary condition. This report suggests a method of analysis for estimating the unsteady wind direction, using the local maximum and the local minimum for the time series of wind direction in natural wind. As a result of analysis, we understood that the fluctuation of wind velocities showed a rising tendency by the more change of wind direction.

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To simulate atmospheric diffusion for a period of one hour, oscillating blade cascade equipment was developed by the author. When the blade cascade was oscillated randomly, distributions of mean wind velocity and turbulence intensities, and turbulence spectra were similar to those observed in the atmospheric boundary layer. However, since all blades were driven by only one servomotor, all blade motions were the same. Therefore, turbulence coherence in the lateral direction was much greater than that of the natural wind. To improve the disagreement of coherence, independently oscillating blade cascade equipment was developed. Each blade has its own servomotor; hence all blades can be controlled independently. Random angular time series of blades were generated from the atmospheric spectrum, coherence and phase functions by the multidimensional auto regression method. Turbulence coherence and turbulence spectrum density functions of the flow generated by the oscillating blade cascade, were found to be in good agreement with observations in the atmospheric boundary layer.

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Direction-changing flow was generated by a row of oscillating vertical plates placed at the entrance of the working section of a wind tunnel and its characteristics were examined. The distribution of mean and r.m.s. value of the velocity components became uniform at downstream position 4 times the plate length. At this position, the lateral component v(t) of the velocity had simple characteristics^: it had the turbulence intensity of 9%, fluctuated with the oscillation frequency f0 of the plates, and convected downstream. However, the longitudinal component u(t) had complex characteristics^: it had the turbulence intensity of 10%, and had frequency components at a few times of f0. The distribution of cross correlation Cuv(0) of u(t) and v(t) was not uniform.

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A quasi-grid method was devised to realize a certain range of Reynolds number of homogeneous and quasi-isotropic turbulence in a multi-fan wind tunnel. This method allows the Taylor-microscale Reynolds number R_λ to vary from 200 to 500. Characteristics of the inertial subrange were investigated in comparison with a previous study. The one-dimensional Kolmogorov constant α₁ was decreased with R_λ and reached about 0.6 at R_λ∼400.

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To produce high-Reynolds-number turbulent flow within a limited entry length of a wind tunnel, a driving mode of a multi-fan wind tunnel is applied. In that mode, grid-like distributed fans are actively driven (“partially-active mode”). A turbulent signal synthesized from the Karman-type spectrum formulation and sinusoidal signals are fed at lower frequencies to the fans. It was found that there is no trace of extension of the inertial subrange due to low-frequency disturbances.

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To simulate the planetary boundary layer, an innovative wind tunnel of multi-fan type is applied, where the airflow is driven by an array of fans (11 rows,9 columns), each of which is independently controlled by a computer. First, the turbulent boundary layer is generated by using a barrier or spires, and some of the resulting statistics are taken as targets. Next, to obtain the target statistics, turbulence is passively generated by a multi-fan wind tunnel with activated and inactivated fans appropriately arranged without using barriers, spires or roughness. The most appropriate arrangement is determined by trial and error, so that the statistics of turbulence by the multi-fan wind tunnel is in good agreement with the targets.

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The present experimental work aims to clarify the flow structure of the microburst. Firstly we investigate the cause why a damaged area by a microburst spreads in the shape of arc by flow visualization. Secondly we measure the flow field around the microburst by using the PIV method. The downdraft was simulated by salt water falling in a water tank. Visualized flow patterns showed that the shape of the actual damaged area resulted from the inclination of the downdraft due to horizontal winds such as rear inflows converging into a squall line. The maximum velocity was observed in the outflow proceeding downwind of the horizontal wind. Such characteristics and flow pattern of the simulated microburst is quite similar to those of actual microbursts observed by Doppler radars. The vortex formed at the front of the downwind outflow was almost twice as intense as that of the upwind one.

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The Schlieren method is an effective way to visualize the thermal flow under the condition of low velocities. This research aims to clarify the relation between the Schlieren images and the temperatures by using thermal stratification wind tunnel. As a result, when rooftop of the single building was heated, the extent of thermal influence could be obtained by the Schlieren images. In the case of 2D-buildings with heated ground, the relationship between the vertical temperature gradient and the brightness devised from the Schlieren images were clarified.

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As the simulation (experiment) technique of a physical phenomenon, there are a numerical computation, a model experiment, and the hybrid technique of both methods. The hybrid technique was proposed by Hakuno(1968), and have been applied in various fields. For wind engineering field it have been applied to the wind tunnel experiment by Kanda(1994). In this study, the hybrid experiment technique is applied to wind affected structures that have complicated vibration damping equipments. Although it is easy to carry out numerical modeling of the tuned mass damper which consists of the simple mass and the spring elements, prediction of the characteristic at the nonlinear nature of fluid to the time of large amplitude and prediction of the action at the time of random vibration are comparatively difficult for the tuned liquid dampers that are applied sloshing of liquid. This study is aiming at development of the hybrid oscillating experiment system for evaluating such dampers.

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In many cases of usual transmission lines galloping simulations, steady aerodynamic coefficients of ice-accreted transmission lines were generally applied and aerodynamic forces were approximated as quasi-steady ones. However, to perform more realistic simulations, it seems that the coefficients data ever obtained are not enough, and characterictics of unsteady aerodynamic coefficients should be invetsigated. So in this study, two types of wind tunnel test were conducted to take an accurate measurement of steady and unsteady aerodynamic coefficients of 4-conductor bundled and single conductor section models with a piece of artificial accreted ice whose profiles were clearly defined. These coeffcients were examined between steady and unsteady, as well as bundled and single conductors.

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The characteristics of wind forces on sunblinds and the characteristics of the vibrations were investigated through full-scale measurements in natural wind. The sunblinds were installed on the outside walls of a building. The results obtained from this study are as follows: 1. The mean and fluctuating wind forces (r.m.s) on the sunblinds were small, but the peak wind forces, which occur intermittently, were large. 2. The maximum peak force coefficient was about 1, and acts upward on the sunblind set on the front wall. On the sunblind on the sidewall, the maximum peak force coefficient was the same but downward. 3. The wind responses of the sunblinds were large when peak wind forces occurred.

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The characteristics of a separated shearlayer above a roof of a cubic model and wind pressure on the roof are experimentally studied by a wind tunnel test. The flow was measured by Particle Image Velocimetry (PIV) system and simultaneous multi-pressure measurements on the roof surface were also performed. As a result of the measurement, quantitative structure of a circulation flow above the roof was presented. The separated shearlayer height was proportional to the parapets height. The characteristics of a wind pressure on the roof were strongly influenced by the height of separated shearlayer and magnitude of reverse flow.

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The aim of this thesis is to clarify the generation mechanism of gust force due to fluctuating flow. In order to discuss the aerodynamic admittance of pitching moment and to investigate the influence of body motion on gust force, the surface pressure around 2-D model with rectangular section of B/D=5(B:chord length, D:depth of the section) were measured in the artificially generated 3-D and 2-D fluctuating flow. It is observed that the unsteady surface pressure in 2-D sinusoidal flow corresponds well to the pressure under pitching motion in uniform flow, which leads to the close relationship between the Kűssner and the Wagner problems. As for the influence of body motion , the independence of the gust force and the motion –induced force has been confirmed.

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The transmission of disturbance generated near the stagnation point to the surface pressure fluctuation of a flat rectangular cylinder was investigated by using periodic weak disturbances, whose frequencies were 13Hz and 16Hz. The expansions of corresponding components were detected in the fluctuating surface pressure and the wind velocity distributions near the surface were measured also. As the results, it was clarified that the increase of the correlation scale of fluctuating pressure to span-wise almost was caused by the extension of the vortexes to span-wise above the reattaching region.

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This paper presents characteristics of wakes behind the vibrating three-dimensional square prism. In this study, in order to identify the instantaneous vector image corresponding to the given across-wind deflection, Particle Image Velocimetry (PIV) system is applied with synchronized laser displacement measurements.It can be noted that the distance of downstream stagnation point from the leeward wall (X_d.s.) depends on the characteristics of approaching flow such as the intensity of turbulence and the mean velocity. In the turbulent flow, the distance X_d.s. is fairly stable. On the other hand, in the uniform flow, the distance X_d.s. rapidly gets the smallest value when the vibrating prism is subject to the vortex shedding.The behavior of wake just behind the vibrating prism has been of interest. By means of synchronized measurements, it is observed that both the reverse flow and the entrainment flow are periodically generated coinciding to the vibration.

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A research was conducted to measure the 3-D golf ball flight trajectory under atmospheric boundary layer. 3-D flight equations were already confirmed by still air flight experiments in our research. In this time, we performed offshore experiments of golf ball shot and measured flight distance. Wind velocity profile distributions were measured up to 5.5m high. To estimate wind velocity at higher position of golf ball flight, a logarithmic low was applied. As a result, 3-D flight distance became possible to be calculated under atmospheric boundary layer.

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This paper deals with a study on calculating unsteady aerodynamic forces of Rectangular Cylinder with Slenderness ratio of 1:13 for bridge deck section using computational fluid dynamics (CFD).The large eddy simulation (LES) with the Smagorinsky sub-grid scale (SGS) model is applied for the turbulent model. The IBTD/FS finite element formulation is applied for the methodology of the numerical flow simulation. For a treatment of the flow around an oscillating structure, the whole domain rigidly moves the same translational and rotational motions as the structural motions without any deformation of the finite element mesh. In order to confirm the effectiveness of present technique, the flow analyses around a plate (side ratio 13) with vertical and rotational forced motions were performed, and present results were compared with the theoretical solutions.

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