Four typhoons (Chaba, Meari, Songda and Tokage) hit the Kyushu area in 2004, and many residential houses and buildings suffered damage. Typhoon Songda (T0418) recorded wind speeds almost equal to previous peaks in various places in Kyushu. However, as compared with the big typhoons of the 1990s, such as Mireille (1991), Yancy (1993) and Bart (1999), the associated damage of residential buildings and power transmission facilities due to Typhoon Songda was not so big.The big gust factor is known as one of the features of Typhoon Mireille (T9119). The subsequent Typhoon Yancy (T9313) and Bart (T9918) also showed big gust factors, evident in the high winds in many regions of Kyushu, and many power transmission facilities suffered extensive damage. In this paper, the typhoons in the 1990s and 2004 are compared, focusing on those gust factors and using the wind data of a high-density wind observation system, NeWMeK. As a result, it was found statistically that the gust factors of the typhoons in 2004 were smaller than those of Bart in a high wind zone exceeding 30 m/s.

View full abstract

Numerical simulation of a flow field around Miyajima Island during typhoon 0418 was carried out. The calculation was done by PSU/NCAR MM5 and RIAM-COMPACT. The calculated result shows that the flow come down fron the reward mountain during the nutral atomosphric condition.

View full abstract

We have the statistical analysis for the amount of short time differences of wind speed, in order to discuss the criteria of regulation rules for railway operation under strong winds. We have two wind observation sites, a bridge on the sea, and a plane neighboring a mountain. We obtain the histograms of the differences of 10-minuite-maximum wind speed and 5-minuite- maximum wind speed based on the weather conditions classified into under the typhoon, in front of the front, rear of the front, under the winter type, and the others. As a result of the analysis, we find that there is a little variation on the histograms depends on the weather condition, and it is equal to or smaller than the variation depends on the observation site.

View full abstract

The distribution of surface roughness in the city area can be estimated by the GIS data. And, the characteristics of the drag coefficient have been investigated based on the data obtained from a series of wind-tunnel measurements in a simulated urban roughness. Consideration is focused on the standard-deviation height of roughness. A model formula for the drag coefficient is proposed as a function of the roughness parameters, i.e. the roughness density, the mean and the standard-deviation of roughness height. This model is used for estimating the exponent of the power law.

View full abstract

The turbulence structure and the transport process of various types of material in thermally stratified turbulent boundary layers have not been sufficiently understood yet, because the flow characteristics are sensitively deformed by the buoyancy effect and become very complicated. In this research, we carry out LES analysis of the spatially-developing stably stratified turbulent boundary layers and investigate the streamwise variation of turbulence structures. Also, through the comparison with the turbulent channel flows which was simulated using the LES technique by Armairo and Sarker(2002), interesting features of a spatially developing stable boundary layer are clarified.

View full abstract

Complex heat transfer fluxes occur in the urban canopy layer on typical summer days. It is important to clarify the heat and momentum flux on the urban surfaces. The experiment was performed in the thermally stratified wind tunnel in Tokyo Polytechnics University. Experiment was conducted on 8 cases of unstable flow. Bulk Richardson number was –0.268(US1) to -0.02(US4) on smooth surface and –0.262(UR1) to –0.024(UR4) on rough surface. To measure flow temperature, cold-wire was used. Wind velocity distribution was measured by using 2-D LDA. Thickness of turbulent boundary layer is 0.1m to 0.25m on smooth and rough surface. Thickness of thermally boundary layer is same as turbulent boundary layer. The value of momentum flux is increase with the decrease of stability. Vertical heart fluxes of near the surface indicate positive value. It shows create turbulence by buoyancy. The value of vertical heart fluxes on rough surface larger than on smooth surface.

View full abstract

The diffusion properties are strongly affected by thermal stratification in atmosphere. A lot of field observations about the relationship between diffusion properties and thermal stratification in the boundary layer have been conducted. In addition, many researchers have developed diffusion models based on the result of above observations. However the results of the field observations may include significant uncertainty. Therefore, highly accurate experiments in the laboratory are required. The authors have conducted wind tunnel test of heat and momentum flux properties under various thermal stratification conditions by LDV (Laser Doppler Velocimeter).In this study, 4 experimental patterns were conducted. Roughness height is 15mm and vertical profile measurement distance is 10mm pitch from 10mm to 400mm. The temperature profiles, the wind velocity profiles, the heat and momentum flux profiles have been observed.The result of the wind tunnel experiments showed that the profiles were variously changed depending on temperature conditions of the floor and the wind flow.

View full abstract

A newly designed wind tunnel that can fluctuate the wind direction was manufactured on an experimental basis. The tunnel utilizes the control of pressure slope direction. The open and close of the shutters at the inflow and outflow ducts are manually operated, and that resulted in the wind speed fluctuation at the same time of the wind direction change; but wind direction could be changed as planned in general.

View full abstract

Ten typhoons landed in Japan in 2004. Three typhoons (Chaba, Songda, and Meari) hit the Kyushu area, Japan. Residential houses, public facilities, and power transmission equipments suffered severe damage. During Typhoon Songda, strong winds exceeding 50 m/s were observed at many observation points of NeWMeK, and more than 12,000 houses were damaged in the Kumamoto Prefecture.The Saga Prefecture was distant from the path of Typhoon Tokage, which did not strike Kyushu island; nevertheless, associated structural damage in the area due to the typhoon was most severe in Kyushu. In the Saga Prefecture, 1,429 houses were damaged. A wind known a katabatic wind in the area blows from the northern mountains in winter. The strong winds may have blown with the north wind associated with Typhoon Tokage. We report the damage associated with the typhoons in Kyushu.

View full abstract

The strong wind disasters of Shikoku region due to typhoons in 2004 were reported. Especially, the human damages were caused by neglecting strong winds. To reduce the wind disasters, it is important to enlighten some usual things, such as, to stay indoor when typhoon come, to wait to treat the damage during strong wind, etc.

View full abstract

Ten Typhoons attacked to Japan in 2004, that is the record of the number. Many damage on buildings occured due to high wind assciated with Typhoons. Causes of the damage shall be identified, and should be reported in order to reduce such damage.

View full abstract

The accident to which the hotel roof dispersed occurred in the west of Shiga Prefecture OUMI-HACHIMAN CITY due to the strong wind induced by typhoon 0406 on around June 21th 13:10 of 2004. The roof came flying to the overhead wiring of Tokaido Shinkansen behind an advertising tower, and damaged it. The dispersing roof reached a rear overhead wiring without colliding with an advertising tower of 14.6m in height on the leeward side. In this research, it aims to clarify the possibility of dispersing without colliding with the dispersion condition of the roof and the adjoining building by executing the wind tunnel experiment that examines the reduced scale rule closely.

View full abstract

Gust wind considered to be caused by a tornado occurred around 11:15 p.m. on September 29, 2004 in Toyohashi City, Aichi prefecture. 183 residences suffered damage (2 completely collapsed, 10 partially collapsed and 172 lightly damaged). In Toyohashi City, four tornados also occurred in 1999 and caused very serious damage. A tornado was generated in Komatsubara town near the Pacific Ocean shore of Toyohashi City, and damage was seen over about 6km to near the Oiwa town.In this paper, the results of questionnaire investigation to the sufferers from a tornado was reported.

View full abstract

When buildings receive damage by the natural disaster in general in Japan, the Japanese damage potential scale (complete destruction and partial destruction) is performed to the damage. This standard of the high wind damage is also applied as it is as for the seismic damage and the flood damage, etc. However, the majority of high wind damage of buildings is damage of the exterior material, and it is thought that the grasp of the situation of the high wind damage is difficult in Japanese damage potential scale. Then, it proposed the new damage potential scale limited to the high wind damage, and the utility was confirmed to be applied to the last year's typhoon damage.

View full abstract

Natural disasters have severely caused collapse of structures and loss of human lives every year. Such disasters lead to tremendous losses of economy and society in each country. There is a similar trend of economic and social aspects between Japan and the United States. This paper presents the comparative study of wind disasters between Japan and U.S.. The change in fatalities due to natural disasters shows a trend depending on year in both Japan and U.S.. The number of fatalities decreases while the population significant increases from year to year. In addition, economic losses due to disasters are increasing recent years. The probabilistic predictions for frequency and magnitude of future events are also examined for natural disaster mitigation.

View full abstract

In recent years, the impacts of flying debris dispersed by the windstorm cause much damage to buildings. And it is important to grasp precise aerodynamic characteristics of debris. In the past researches the trajectories of flying debris are predicted by means of the aerodynamic forces derived from quasi-steady assumption. But theoretical results derived from quasi-steady assumption cannot take into account the interaction between rotating motion and wake turbulence. This means quasi-steady theory cannot be used for a flying plate with rotation.In this study CFD technique is built in order to predict the action of flying debris without quasi-steady assumption. In order to compute fluid flow around flying object, an overlaid grid system is introduced. We clarify physical mechanism of flight after due consideration of wake turbulence.

View full abstract

In this study, high-resolution numerical simulations on the local wind system in an urban canopy are carried out by using two classes of numerical models, and the features of severe winds in various buildings are examined. Wind fields in an urban scale are simulated by using a mesoscale meteorological model, while turbulent flow fields within the urban canopy are calculated by using large-eddy simulation model that incorporates explicitly the effects of buildings and structures. In the LES calculations high-resolution GIS data are used, and thereby realistic surface roughness in the urban area is reproduced. This research demonstrates more local and gusty winds within the urban canopy than simulated only with a mesoscale model, which will improve the prediction accuracy of a severe wind disaster.

View full abstract

This paper describes CFD simulations of flowfield around a high-rise building surrounded by the low-rise city blocks. Wind tunnel experiments in boundary layer using split-film probe were carried out by the present authors to obtain data for assessing the accuracy of CFD results. In the CFD simulations, influences of calculation conditions such as size of side and upper calculation region, grid system, range of surrounding city blocks were investigated. CFD results with k-e model well agreed with the experimental result at the high wind speed points. The influences of various calculation conditions on prediction accuracy are discussed in detail in this paper.

View full abstract

abstract

View full abstract

This study investigates the spatial distribution of turbulent time scale used in liner revised k-e models around a bluff body. 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 model, W model and S-W model, proposed by Nagano et al.

View full abstract

A scale-dependent dynamic Smagorinsky (SDDS) model proposed by Porte-Agel et al. (2000) was introduced into the large-eddy simulation (LES) of a turbulent flow over a two-dimensional steep hill in order to improve the poor prediction accuracy of the scale-invariant dynamic Smagorinsky (DS) model reported in our previous paper (2004). The prediction accuracy was assessed by comparing the results with those from an experiment by Ishihara et al. (1998), the standard Smagorinsky model, and the DS model. On the whole, the SDDS model gives accurate predictions and improves the poor prediction accuracy of the DS model; however, the improvement is somewhat insufficient. Furthermore, the computational cost of the SDDS model was much higher than that of the other two SGS models, mainly due to the cost of solving the polynomials for the scale-dependence parameter.

View full abstract

Large eddy simulation (LES) is carried out to investigate the turbulent boundary-layer type of flows over a hill-shaped model with a steep slope. Also, we focus on the surface condition of a hill, such as vegetation effects as well as curvature effects. In order to model the vegetation effects for LES, we employ the feedback forcing method proposed by Goldstein (1993). In this model, the equation of motion for trees or grasses is coupled with the Navier-stokes equation, so turbulence in the vegetation canopy can be numerically expressed. Instantaneous velocity profile of turbulent boundary layer on the corresponding surface is imposed at inflow boundary. Both the computed results over the hill with and without vegetation are in good agreement with Meng's (1998) experimental data for a rough and a smooth hill. Also, the effects of vegetation on turbulence statistics, including the coherent structures above the vegetation, are clarified.

View full abstract

Large eddy simulation (LES) was performed for stably stratified flow over a wavy wall. Low-Mach-number approximation was applied to treat the effects of density variation. Discussion was given to the mechanism of turbulence transport, and stable stratification was suggested (1) to increase the energy transport between Reynolds normal stresses far from the wavy wall, and (2) to reduce the spatial transport of turbulence near the wall. In the transport mechanism clarified here, however, the structural change by stable stratification was small, and flow structures were not markedly changed as well.

View full abstract

The anisotropic k-l turbulence model has been implemented in RAMS model. Using the k-l model, a numerical simulation of air flow around Mt. Tsukuba has been performed. The results of frequence of appearance about wind direction shows good agreement with the field observation.

View full abstract

In this paper, the relationship between gust factor and wind speed ratio against a reference wind is considered. Ground level winds have been measured at 15 points in 5 areas, Tokyo. Wind data observed at 74.5m high by Tokyo Meteorological Observatory is used as reference wind. The equation of the gust factor related to wind speed ratio made comparison with functions which were proposed by Hongo et al, Nishimura et al, Satake et al, and Murakami et al. Also the proposed equation was applied to estimate the wind environment based on Murakami criteria, ranks of predicted wind condition are obtained to be equivalent and/or significant little over to the obserations. Then it is concluded that the proposed equation of gust factor is reasonabl.

View full abstract

It was reported that the annually averaged wind speed in Fukuoka is decreasing gradually after 1980. In this study, the relation between the decrease and the heat island effect has been investigated by means of data-analysis.

View full abstract

Even inside urban areas, there is a possibility that the accidental spilage of hazardous materials for the transportation and storage and intensional release by chemical and biological terrorism occur. Therefore, the characteristics of concentration fluctuation around regularly arrayed cubes (in-line and staggered) have been studied by wind tunnel and field experiments. However, taking into consideration aspects of actual urban canopy, the height and width of buildings, their arrangement, the spacings between them and the width of the streets change variously. Therefore, aspects of actual urban roughness are so complicated that characteristics of plume dispersion in surface layer are very different from those of plume dispersion in typical urban model arrayed regularly. Therefore, we use LES(large-eddy simulation) to investigatethe the chracteristics of flow and plume dispersion in actual urban area and estimate peak concentrations based on various kinds of surface roughness.

View full abstract

The aim of this study is to predict the concentration distribution of air pollution emitting from sources near the ground within urban area. This study consists of field measurements and wind tunnel experiments. The field measurements were conducted at Ikegami-Shinmachi area in Kawasaki in vicinity of Tokyo using SF6 as the tracer gas. Metroporitan Expressway is licated along SW-NE diagonal of the study area around Ikegami-Shinmachi intersection. There is the local higyway running parallel to the expressway and the local road cross to them. Diffusion fields were simulated in a thermally stratified wind tunnel at the IIS. The city model was modeled partially at a scale of 1:600. The dispersion of emission from a line source near the ground, a ethylene was used as the tracer gas. The results of the wind tunnel experiments showed good agreement with the results of the field measurements.

View full abstract

Although there is a measure of automobile emission control, the air pollution contributed by NOx in a large city has not been lessened. Furthermore, since the cogeneration system in urban areas is increasing, the exhaust fume containing NOx is largely discharged near the buildings. Past research has proposed some simple models for prediction of pollution concentration; however, those equations do not take some architectural factors such as the form of building, the configuration of building, street widths, relative positions of pollution source into account. Therefore those models are not generally applicable to the built environment.. Practically, in order to predict the concentration of pollution in urban space, wind tunnel test and CFD simulations are often used. CFD simulations have been increasingly applied to predict and analyze the air pollution and wind environment in built-up areas. As the first step of this study, we performed CFD analysis using various k-epsilon models to verify the results of wind tunnel experiments recorded in the past and evaluated the accuracy to predict the diffusion of contaminant substances.

View full abstract

Increase of air temperature due to urbanization, i.e. heat island effects, is getting very serious in Japan. This study aims to clarify the regional characteristics of heat balance in an urban space of a city. Since most of major cities in Japan are located at coastal areas, special attention is paid to the contribution of sea breeze to the heat balance in urban area in this study. The spatial distribution of heat budget inside Sendai is drawn, as "heat balance map". This map shows the area where the influence of sea breeze is larger than those of heat generated from ground surface and artificial heat release. In this area, it is effective to introduce sea breeze into urban areas by matching the building arrangement with wind conditions.

View full abstract

In the prediction of the indoor thermal environment and the heat load, meteorological data obtained at weather stations in each city are usually utilized as meteorological conditions. However, there exists considerable difference in the local climate in each region inside a city. So it is necessary to consider the regional characteristics of meteorological conditions in order to improve prediction accuracy. This study aims to examine the influence of regional characteristics of local climates inside Sendai city on the performance of cross-ventilation in residential houses from the viewpoints of the indoor thermal environment and the cooling load based on the numerical analysis using TRNSYS. Here, the results of numerical analysis of mesoscale climate were utilized as input data of meteorological conditions for TRNSYS.

View full abstract

Focused on the velocity of wake after the three dimensional vibrating square prism that changes dynamically and complexly, the systematic structure concerning the fluctuating velocity field of the wake at vortex shedding was evaluated by the POD analysis. The fluctuating velocity field was numerically obtained by the Dynamic PIV system which includes double pulse YAG laser, high speed camera and so on. First three modes look like the distribution shape of standard deviation, and the contribution rate of low level modes at vortex shedding is larger than that at non-vortex shedding. First and second modes seem to play significant roles in correlation between principal coordinate of each mode and deflection of vibrating square prism.

View full abstract

The characteristics of a flow around a cubic model in a turbulent flow are experimentally studied by a wind tunnel test. Wind pressures at the windward edge decrease when velocity increase outside of the separated share layer. Negative pressures decrease at the center part of the roof when a strong circulation was formed above the roof. Wind pressures recovered at the leeward edge when a separated share layer reattaches at the leeward edge.

View full abstract

Applicability of LES (Large Eddy Simulation) technique to wake flows past a bluff body should be clarified in order to improve numerical accuracy for the estimation of aerodynamic forces and pressures acting on a bluff body. Here, we carry out both of LES and PIV (Particle Image Velocimetry) for wake flows past rectangular cylinders with depth/breadth ratio ranging from D/B=2.00 to 3.00 at Re=2,000 and 20,000, which sensitively change turbulence structures due to flow separation and reattachment. In LES, we use the dynamic Smagorinsky-type SGS model. Firstly, at Re=2,000 where the pure turbulent viscosity is realized, the accuracy of the SGS modeling for prediction of not only aerodynamic characteristics but also turbulence statistics in the wake of rectangular cylinders are examined in comparison with PIV data. Furthermore, at Re=20,000 where the numerical dissipation must be incorporated, we clarify unfavorable effects of the numerical dissipation on the turbulence structures in the wake.

View full abstract

Wind flows around a row of rectangular cylinders are computed in order to simulate wind-induced noise from balustrade. Obtained time histories of wind-forces acting on each cylinder are used for reproducing sound pressure. The peak frequency of the noise is higher than that of vortex shedding and induced when the separating shear layers from cylinders keep close to their side surfaces.

View full abstract

In turbulent simulation by the finite element method, when using the wall function and dealing with the tangential direction velocity of nodes on the body boundary as unknown variables, the tangential direction cannot be determined uniquely at the corner of nodes on the body. In this study, we considered that the tangential direction at the corner of the body will change according to the flow field. We evaluated the tangential direction of the velocity at the corner node by using of local velocities and inclinations of adjacent element edges along the body. By this way, we simulated a flow around the two-dimensional square cylinder, and computed aerodynamic forces acting to the square cylinder which are enough close to those of existing studies.

View full abstract

The rectangular cylinders are bluff for the flow field, and the aerodynamic phenomena relate to various vortices, such as Karman vortex and one-shear-layer related vortex. Therefore, the rectangular cylinders, whose side ratio is 4, relate the multiple aerodynamic vibrations. In this study, the Proper Orthogonal Decomposition (POD) is applied to the unsteady pressure around oscillating rectangular cylinders, and the structure of flow field around oscillating rectangular cylinders are investigated. Moreover, it is shown that the mode shapes, which are given by POD, show the instantaneous pressure coefficient.

View full abstract

Flow-induced in-line oscillation of tandem circular cylinders has been experimentally studied by free-oscillation tests in a wind tunnel. The upstream cylinder model with the reduced mass-damping parameter Cn=0.99 was supported by eight coil springs to be moved in the in-line direction, and the downstream cylinder model was fixed. The gap between the upstream and downstream cylinders was changed from s/D=0.3 to 2.0. We measured the responses of the model in in-line oscillation and the vortex-shedding frequency. The flow around tandem circular cylinders was visualized by the smoke-wire method. For the gap ratios of 0.3≤s/D≤1.5, the single wide excitation region appears, and the exciting oscillation region extends up to reduce velocity of Vr=2.7. The oscillation characteristic is similar to the oscillation response of the single circular cylinder with a splitter plate. The oscillation of the excitation region is mainly induced by the symmetry vortex shedding. The upstream circular cylinder with the gap ratios of s/D≥2 has two kinds of exciting oscillation mechanisms, similar to that of the single circular cylinder. The vortex shedding during the in-line oscillation shows symmetric and antisymmetric patterns in the two excitation regions, respectively

View full abstract

Study of mean wind pressures and forces acting on yawed circular cylinders with small aspect ratio are examined by wind tunnel tests. In this report, mean drag force coefficients, mean lift force coefficients and mean pressure coefficients at middle span of the model with yawed angle are described, and Reynolds number effects on these value are discussed.
The mean drag force coefficients decrease near Re=300000 regardless with yawed angles. The mean lift force coefficients occur at these Reynolds number ranges except a yaw angle 45 degrees.
The mean lift coefficients are caused by differences of the wind pressure between sides of model.

View full abstract

Study of mean wind pressures and forces acting on yawed circular cylinders with small aspect ratio are examined by wind tunnel tests. In this report, the distributions of mean drag force coefficients and mean pressure coefficients along span axis caused by yaw angles are described and Reynolds number effects for variation of those values are discussed.
The mean drag force coefficients on the cylinder with a yaw angle 0 degree are almost a uniform value along span axis regardless of Reynolds numbers. When approach flow is not at right angles with a cylinder, , the drag force becomes smaller according as the measurement location is more leeward..
For Re=200000 range, the mean pressure coefficients change according to measurement positions except for a yaw angle 0 degree. The wind pressure distribution at a most windward position is different from ones at other positions.
For Re=400000 range, the mean pressure coefficients have not change by the measurement position for all yaw angles.

View full abstract

Magnetic force fluctuations acting on a sphere suspended in flow without any support interference with Magnetic Suspension and Balance System were measured. Two kinds of the fluctuations in drag direction were observed. They are 0.05 and 0.08 in Strouhal number. We observed that sphere drag reduced much suddenly for a short time at Reynolds numbers around critical one, and also observed that magnetic force perpendicular to drag acted on sphere rotationally near critical Reynolds number.

View full abstract

In stormy days, there are many accidents of pedestrians who are holding an umbrella. It can be said that the behavior of the umbrella in wind is a problem related to human safety. We conducted a wind tunnel experiment basic characteristics of aerodynamic forces exerted on an umbrella. From the measurement of the static forces, it is shown that pitching moments is exerted on an umbrella leaning toward the upwind although the aerodynamic forces are small. On the contrary, when the umbrella is leaning toward downwind, the aerodynamic forces are large but stable.

View full abstract

In stormy days, there are many accidents of pedestrians who are holding an umbrella. It can be said that the behavior of the umbrella in wind is a problem related to human safety. We measured the characteristics of unsteady aerodynamic force under air currents with stepwise change of velocity. The inclinations of the umbrella are fixed at 0 degree and (plus, minus) 45 degree. As a result, when the umbrella is inclined to the upwind, the aerodynamic force. On the contrary, when the umbrella is inclined to the downwind or perpendicular, direction of the resultant force suddenly changes.

View full abstract

There is an artistic sculpture made for commemoration of Second World War victims in Romania, which is called Endless-Column. The total of height attains about 30m, but the sectional dimension is small that's why this structure forms a very slender shape. In spire of its slenderness, the column is very stable against wind, and the reason should be found in the structural components of the column. This column consists of some modules of a geometrical shape. This shape of modules had been used in constructions from ancient because of the stability. That's why this research will clarify from point of wind engineering if this construction is stable or not.

View full abstract

The aim of this study is to clarify the generation mechanism of gust force due to fluctuating flow.In order to discuss the reason why the span-wise coherence of fluctuating pressures on two-dimensional bluffsections is larger than that of fluctuating wind velocities,the surface pressure around 2-D model with rectangular section of B/D=5were measured in the artificially generated 3-D fluctuating flow.In conclusion,it is considered that unsteady characteristics of the separation bubble influences on spatial structures of the surface pressure.

View full abstract

In this study, the propergation of a weak periodic disturbance to pressure fluctuations on a flat rectangular cylinder was investigated to understand the mechanism of the expansion of the spatial correlation of the fluctuating lift. By the ensemble averaging of the fluctuating pressures, it was clarified that the strength of the disturbance given to the stagnation point didn't affect to the region of the propergation of a periodic disturbance to pressure fluctuations.

View full abstract

Standing on consideration that an aeroelastic vibration of the bridge isphenomenon caused by separation flow at leading edge of a structure,Kubo started his research on suppression of aeroelastic vibration bycontrolling the separation flow at the leading edge and named it as"Separation Interference Method". The Separation Interference Method is the method to suppress theaeroelastic vibration caused by the separation flow, through separationinterference effect that is generated by setting the first and thesecond separation points around leading edges of the structure. Although the usefulness of the Separation Interference Method isconfirmed, the detail mechanism is not yet made clear. Therefore, thepurpose of the present research is to make clear the mechanism ofSeparation Interference Method.

View full abstract

This paper describes the aerodynamic effect of the inclined lower flanges of two-edge girders, which have economical and structural advantages for future long span cable stayed bridges. The characteristics of the flutter instability of two edge girders, based upon a series of wind tunnel tests, are discussed. Then, it was clarified that the lower geometrical shapes of two-edge girders play an important role on characterizing the aerodynamic stabilization of two edge girders.

View full abstract

Since flutter phenomenon is catastrophic oscillation, its stabilization is most important in designing of long span bridge girders. The accurate apprehension on the vibration mechanisms is essentially important to stabilize them. In this research, wind tunnel experiments and Torsional/Heaving 2DOF flutter analysis are carried out, mainly focusing on the bifurcation characteristics of the branch.

View full abstract

It has been discussed about the construction of a super-long bridgeexceeding the span length of the Akashi-Strait Bridge that is thelongest bridge in the present world. To realize the super-long bridge,the research on the aeroelastic vibration of suspension bridge must be advanced in more detail. Although an additional member of fairing so on is often used as one of suppression methods of aeroelastic vibrations, using the additional members for aeroelastic vibration control is not favorable from point of view of cost performance and maintenance. A pentagon cross-section was proposed as a cross section of girder that satisfied cost performance and aeroelastic stability without using additional members for suppression of aeroelastic vibration. In the present paper, the development of bridge girder cross section is dealt with for the super-long bridge longer than the Akashi-Strait Bridge by changing the slope of web of the pentagon cross section through measuring 3-compornent of aerodynamic forces and aeroelastic responses.

View full abstract