This paper shows some phenomena which are variations of wind pressures acting on a circular cylinder caused by rotors. This paper examines the use of rotors for changing flows past a circular cylinder in a wind tunnel. Wind pressures acting on a circular cylinder equipped with rotors were measured to investigate changes of air flows. The ratio of rotor circumferential velocity to wind speed was used as a parameter for comparing drag coefficients and lift force coefficients. Drag coefficients decreased as this ratio increased. Also, the fluctuation of lift forces was significantly affected by the velocity ratio.

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By conventional experiment technique, quantitative evaluation of external force was difficult. Therefore the writers developed New Hybrid Aerodynamic vibration Technique and I enabled the measurement at vibration that Wind external force and the wind pressure which act on Bluff body

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There is few report of the coefficient estimated in an unsteady flow such as a step-function-like gust characterized by its very short rising time. The authors measured wind forces of a bluff body in steady and unsteady flows and made comparisons of both forces. When a step-function-like gust having a rising time of 0.2 seconds acts to a bluff body such as a railcar, a remarkable peak of the lift of the body was confirmed within a very short time of initiation and the peak was 5 to 6 times as large as in the steady flow. And it was found that the peak is strongly affected by the rising time and wind.

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This paper discusses the unsteady characteristics of the conical vortex on a flat roof on the basis of numerical results by large eddy simulation when flow attacks oblique to the roof. First, the present LES model is validated for the prediction of the peak suction on a roof for oblique flow through comparison with the previous experimental data. Next, the unsteady motions of the conical vortex are investigated by use of a flow visualization technique.

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The characteristics of the fluctuating external wind pressures on circular cylinder have been investigated based on the data obtained from a series of wind-tunnel measurements in simulated atmospheric boundary layers. Focus is on peak pressure coefficients of probability density function. A model of the peak factor on the circular cylinder is proposed as a function of the values of skewness and kurtosis. This model is first step for approximating the fluctuating wind pressures.

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When a strong wind occurred, the damage by wind of various structure is reported, and, as for it, the damage such as falls is reported not an exception about prefab houses temporary building. A temporary building is used for an on-site temporary office or storeroom, but the control is needed so that the data that it is necessary are lost when the damage that mentioned above occurs, and expensive machinery may be damaged. However, it is necessary to know what kind of phenomenon occurs in the building outskirts to suggest a control to be concrete. Therefore it is this study and is for suggestion of a wind damage control of a temporary building by grasping the aerodynamic characteristics with a model of a temporary building for the purpose of getting connected data.

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Many low-rise buildings are surrounded by a group of similar buildings, but few researchers have studied the interference effect of surrounding building group on wind loads on the surrounded low-rise buildings [1,2]. A series of pressure measurement wind tunnel tests were performed on flat-roofed low-rise buildings surrounded by similar building group in Tokyo Polytechnic University. This part, Part I, studies the interference effect of a surrounding building group on the distribution of local wind pressure coefficients on the flat roof of a target low-rise building. Part II discusses the effects of plan-area density and relative height of surrounding buildings on the interference coefficients of the worst extreme local and area-averaged suction wind pressure coefficients on a flat roof.

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This paper continues the study of the interference effect of a surrounding building group on wind loads on a flat roof of a low-rise building. Part I studied the interference of a surrounding building group on the distribution of local wind pressure coefficients. The present part discusses the effects of plan-area density and relative height of surrounding buildings on the interference factor of the worst extreme local and area-averaged suction pressure coefficients.

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Comparisons of the internal pressure fluctuation on wind tunnel test and the fluctuation on field mesuarment are shown in this paper. Mean internal pressure coefficients were similar to each other. Maximum value of mean internal pressure coefficient was 0.8. A Cross correlation function between the internal pressure near the wall opening and the external pressure near the wall opening had strong correlation. However, the Helmholz resonance phenomenon was not appear on field mesuarment. It was caused by the fact that the pressure flowed out from a gap.

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Concerning the wind resistant problems for buildings and structures, wind tunnel test and numerical simulation have been conducted out of consideration of effect of thermal stratification. However, it is confirmed that the observed wind profile in the typhoons is different from the wind profile in the boundary-layer type of flows and determined by strong convective effects. In this study, we numerically generate approaching flows with the effect of thermal stratification. Under these approaching flows we conduct numerical simulation for the flows around a 3D square cylinder. It is recognized that the flow field is much changed by the effect of thermal stratification and the position of the vortex on the side and the rear of the cylinder varies with the thermal conditions.

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Time of an overturn of a train and a car induced by sudden gust is calculated when a tornado pits the train or the car. In the calculation, an inertia force can be considered in the equation of the motion in addition to the static wind force and gravity force. As the result of the calculation, the following results are obtained. (1)The overturning time increases in proportional to root of size of a train. (2)The overturning time of the train is about 1 to 2 seconds. (3)The overturning time increases in proportional to the ratio of the train density to air density and the size of the train.

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This study produces the wind tunnel device which can reproduce the direction of the wind change characteristic that natural wind has experimentally, and there is it for the purpose of clarifying a generated current of air characteristic. Here, I use the shutter which I can open and close by the computer control that was able to possess a part of the direction of the wind change wind tunnel which I produced experimentally and report an examination result of direction of the wind change characteristic when I used opening and shutting timing and it which can change as the stable wind velocity by the direction of the wind.

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An unsteady aerodynamic force characteristic to act on a bridge section becomes necessary for analysis of a wind-resistant characteristic, but it is the present conditions that precision cannot make the measurement of unsteady aerodynamic force better at a low price.Therefore it is this study, I suggested inertia elimination type unsteady aerodynamic force measurement and was aimed at clarifying the measurement precision and problems.I tried it to get more correct unsteady aerodynamic force by grasping influence of inertia by virtual mass in a monotonous model experiment.I suggested an application method to the bridge model which assumed this assay a base and examined.

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Current estimation of peak factor for wind load effects is based on the assumption that they are Gaussian distribution and narrow band process. However this assumption is erroneous in the case of low-rise building structures because the wind load effects have been observed to be generally non-Gaussian. In this paper the theoretical peak factor derived for the wind load effects are discussed and compared with the experimental results.

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This paper is the one that the technique for presuming an appropriate parameter and the presumption example were shown about the building where the tendency with which the response characteristic to the earthquake turbulence and the wind turbulence conflicts for the setting of a structural parameter is remarkable.

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Models of cantilevered stadium roofs were designed and made. Their dynamic characteristics were measured. Then, characteristics of their dynamic response in a smooth flow were investigated. It was confirmed that flutter occurs even to the heavy models in a smooth flow. The onset non-dimensional velocity was about 6. Characteristics of wake were also investigated. A spectral peak appeared at the natural frequency, when the flutter was occurring, but did not when the flutter was not. This suggests that the fluuter is probably associated with vortices induced by scillation.

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Due to a lack of full-scale observations of a tower-supported steel stack, the relation between the growth of the stack's vibration and its aerodynamic damping is not clarified. The authors have got some findings about the growth of the stack vibration, estimating the damping ratio during large vortex-induced vibration using our wind observation data and several new estimation techniques; the stack's total damping is significantly reduced due to the negative aerodynamic damping and the aerodynamic damping sometimes shifts widely in the growth process of the stack's vortex-induced vibration.

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The report focuses on the effects of higher-vibration modes of an elasto-plastic structure on its energy input in a gust response. In addition to deriving a procedure of energy input estimation of a multi-degree structure in an elastic response, the validity of the procedure is confirmed by a time history response of the structure, which is a multi-mass system or a one-mass system, and the effects of higher-vibration modes of the structure on its energy input in a gust response are discussed. Our findings are as follows;
Although the influence of higher-vibration modes in an elastic response ranges from about 10% to 15% its rigidity distribution, the influence is almost fixed in the natural period of about 5 seconds or more. In the elasto-plastic response, it is confirmed that the influence of the higher mode fluctuates widely according to the rigidity distribution.

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This paper discusses the properties of viscoelastic damper during long duration random vibration. In this study, the long duration model of viscoelastic constitutive rule, which is based on fractional time-derivative model & capable for heat transfer analysis, is used to evaluate viscoelastic damper properties such as temperature dependence, stiffness etc. Analytical results show that temperature inside the viscoelastic material body become stable by effect of heat conduction & heat transfer even if the damper is vibrating randomly. In addition, this paper proposes a simplified evaluation method using sinusoidal-wave to substitute random time history data properties. Accuracy of proposed evaluation method is validated by comparing with analysis result using random time history data.

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There are many reports about the trajectory estimation of wind-debris. The report focuses on some effects of gust properties on the fluctuation of the scattering distance of round-like body under a strong wind. The horizontal ranges the round missiles reached are estimated according to several parameters of the gust field. The two dimensional gust fields matching the Karman's turbulent structure are generated as time history data using the multi-dimensional auto-regressive methods. The equation of 2-D motions in the flow fields is numerically solved and a lot of results are statistically processed. It is found that the maximum scattering distance increases with the turbulent intensity or scale.

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The authors developed one method and tried to make clear its suppression mechanism. This method was named by Y. KUBO, one of authors, as Separation Interference Method (SIM). The detail of this method and the reduction mechanism are described in the present paper, taking an instance of a square prism that vibrates. As a result, we showed that circulation vortex between 1st separation point and 2nd separation point was very important for SIM.

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The aerodynamic vibration of bluff bodies are induced by separated flow from leading edges of the bodies. Separation Interference Method (SIM), named by Y.KUBO, one of the authors, is the aerodynamic technique for reduction of the aerodynamic vibration by suppressing the separated flow. It has been clarified that using plates that is placed to normal to the surface of the body at an optimum position is effective as SIM. In this study, the aerodynamic stabilization mechanism of SIM is investigated by using static pressure measurement and unsteady pressure measurement under torsional forced vibration intended for B/D=8 rectangular cylinder. As a result, it is clarified that SIM causes small reattachment length of separated flew from leading edges.

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Many flutter characteristics have been clarified by use of step-by-step analysis. Solutions of it, however, have little discrepancy from those of conventional complex eigen-value analysis which is widely used as flutter analysis particularly after flutter onset velocity. In this research, by considering step-by-step analysis, step-by-step II analysis is proposed, and coupled flutter mechanism is investigated.

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This study aims to clarify the generation mechanisms of dry state galloping instability of inclined Stay-Cables. Recently, a violent cable vibration under strong wind was observed in a cable-stayed bridge in Japan. The factors of that vibration might be the axial flow effect, which is formed in the wake of inclined cable. Two different results are reported. One reports that structural damping is very useful for controlling the aerodynamic vibration, and the other reports that structural damping is not so useful. In this study, focusing on the axial flow considered as the same effect in the point of repression of Karman vortex shedding, wind tunnel tests are carried out in order to clarify the effect of the Scruton number.

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Jumper devices controlling oscillation of jumper lines are often adopted as a part of conductors of a transmission tower. However the vibration characteristics of the jumper devices seem to be complicated under strong winds and the vibration of the jumper devices may cause the oscillation of the tower body and/or the frames. Our vibration tests were conducted to grasp basically dynamic interactions between the jumper devices and the tower. The test results showed that the characteristics of the jumper devices during the device shaking shows different one during the tower shaking. Furthermore some wind observations revealed that the vibration characteristics of the jumper device under strong winds were more complicated than under calm, that is to say, dynamic interactions between the jumper devices and the tower also became complex. Therefore, an advanced numerical analysis considering wind load response and so on requires more information of the dynamic interaction between jumper devices and tower.

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The one of weaknesses of the vibration measurement of a structure is to involve an immense amount of time and effort to wire the cables and so it is difficult to act flexibly to circumstances like a change of a typhoon path. It is obvious that a wireless measurement system has a lot of advantages. No report about application to measurement of a transmission tower is however known, and reliability of measured data by wireless system under a high magnetic field or a strong wind is unknown. The authors measured acceleration of a transmission tower by wireless and wire-carried measurement and made comparisons of both physical data such as a wave shape, standard deviation and power spectrum of the tower. Although attaching collateral conditions of about measurement range of 200m, 500kV transmission tower and under a strong wind of 10m / s, it is confirmed that the present wireless-carried measurement has almost same reliability as the wire-carried measurement.

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The yearly prediction bias is reduced to 0.12 m/sec from 1.32m/sec by the proposed approach in which the effect of complex terrain is considered. The multi time scale power forecasting model gives better prediction than the conventional models, especially in the month that unexpected stop occur frequently.

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We have developed a new wind turbine system that can improve the power generation performance by accelerating the inflow wind. As a result of the field experiment, the power generation in the natural wind showed a higher performance compared with the wind tunnel experiment. In this research, the influence of turbulence to wind turbine performance was examined through wind tunnel experiments, the power output improved in velocity-fluctuating flows and a certain turbulent flow, and decreased in a direction-fluctuating flow. Therefore, if a wind turbine could capture a wind direction change precisely, the output power is expected to be improved in a natural wind.

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Gyromill type wind turbine generally includes an over revolution problem. To inhibit this problem, a revolution speed of wind turbine is controlled by a mechanical break system or an electric-magnetic break system. In this study, to inhibit the over revolution problem, a new gyromill wind turbine, which can be controlled autonomously by changing the wing pitching angle by the centrifugal force, were developed. As the results of this study, it was found that the aerodynamic autonomous control system of the developed wind turbine works very well and this system will bring safer and cheaper wind turbine.

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This paper describes the performance of a H-type Darriues wind turbine with variable-pitch.Our aim is to get basic data to increase the efficiency of small vertical axis wind turbine system by variable-pitch mechanism.The proposed variable-pitch angle mechanism is the four-bar linkage. The feature of the variable-pitch mechanism is to be able to change pitch angles according to the rotational angles of the blades without actuators and the attack of angle of blades become a suitable value.We measured the performance of wind turbines with a NACA63₄-221 airfoil sections by using a wind tunnel.The performance of wind turbine is dependent on the size of turbine, it was found that efficiency of turbine increased and the wind velocity of self-start decreased than that of the fixed-pitch wind turbine by variable-pitch mechanism.

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We have developed a new wind turbine that consists of a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it. We have already succeeded in the practical use for the micro wind turbine (call it a wind lens turbine). We are planning to utilize wind lens turbines to generate the electricity for irrigation and greenery business at a desert area in northwestern China. So, we further developed a more compact wind lens to realize smaller weight and higher output. And we did the field test of new wind turbines. The wind turbine showed power output in field test as high as in a wind tunnel experiment.

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A new semi-submersible floating structure was proposed on which three wind turbine towers would be installed. This paper presented the dynamic behaviors of the 1/150 scaled rigid model experiments in a water tank. To evaluate the dynamic behavior of the floater, regular wave tests were conducted and the responses of floater were measured by using an optical system. The observed surges varied linearly with the wave height in the ranges of periods far from the natural period. However, the surges normalized by wave height had peaks around the natural period, and decreased significantly when wave heights increased. To investigate the effect of the wind turbines to the floater, collinear wave and wind tests were also conducted in the same wave condition, wind speed was set at 2 and 4m/s corresponding the operating and survival case of wind turbine, respectively. The observed surges showed that the peak responses of the floater decrease in the operating condition due to the aerodynamic damping from wind turbine, but there was little effect in the survival condition.

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A FEM code was developed to predict the dynamic behaviors of elastic floating offshore wind turbine systems in the time domain, employing the Morisons'equation to calculate the hydrodynamic drag forces and inertia forces in the perpendicular to the columns of floater, and quasi-steady theory to calculate the aerodynamic forces on wind turbines. Since the relative velocities of the moving element were used to predict the drag forces, the hydrodynamic and aerodynamic damping were automatically taken into account during the simulation. The responses predicted by the proposed numerical model showed a good agreement with experiments, and those by the conventional numerical models were overestimated due to the lack of considering the interaction between wind turbines and floater.

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