The number of telecom facility damages caused by unusual weather is increasing.

In particular,the bundling hangers* are the most number of damages due to unusual weather among the telecom facility of “NTT East”and“NTT West”.

This document explains the influence of strong wind on bundling hangers.

*wire for bundling communication cable.

For installation of overhead communication cables, multiple communication cables are often bundled using a bundling hanger, which is supported by a suspension wire. To estimate the sectional force acting on the joints of the bundling hanger, steady aerodynamic force measurement tests were carried out for each component, and static wind response analysis, in which the contact of each component was considered, was carried out for a full span model. Although the sectional force acting on the hanger changes depending on the boundary condition of the communication cable, the static wind load is not enough to cause the failure of the joints.

Communication cables laid between utility poles are often bundled together with steel wires in a bundling hanger. Bundling hangers may be damaged at joints and communication cables may fall off the hanger due to a strong wind caused by a typhoon. This paper presents the behavior of the communication cable inside the hanger under buffeting by using a dynamic contact analysis for these componets against fluctuating wind load. The obtained results indicate that each componet inside the hanger is displaced integrally, thereby the communication cable press the hanger and cause the enhancement of sectional forces acting on the hanger.

In this study, we estimated the damage probability for each fixed range mesh in the disaster area using the typhoon building damage probability model using the Weibull distribution, and compared it with the presence or absence of damage to examine the usefulness of the proposed model. As a result of constructing a model using the building area ratio instead of the housing density proposed in the past, the damage probability obtained from the data and the estimated damage probability were almost the same. In addition, as a result of calculating the estimated damage probability using the created model and comparing it with the presence or absence of damage, the two showed a good correspondence relationship. Therefore, this model is useful for predicting strong wind damage on building roofs.

Using two representative mean wind speed distributions obtained from experiments using a tornado wind tunnel, we examined how the flight characteristics of flying objects change due to the effect of this wind speed distribution, and also how the flight characteristics (maximum radius of arrival, maximum altitude of arrival, and maximum flight speed) of flying objects change in the wind speed field of the Fujita model used in previous studies.

Many waterspouts occrures in Japan, and sometimes make landfall.

In this study, the effects of surface roughness to tornado-like vortices were studied using CFD method, controling block height and distribution pattern.

When roughness blocks are distributed only the half of the region, the vortex was similar to the case when the same number of blocks are distributed uniformly over the whole region, but for the cases when blocks were tall.

It seems that when the gap of angular momentum among the region is quite large, flow cannot mixed in the vortex.

In this study, the effects of nearby terrain on the wind speed distribution around the complex terrain were investigated. As a result, it was confirmed that the wind speed ratio near the ground surface was determined by the terrain in the immediate vicinity, and the wind speed ratio in the sky was influenced by the existence of the distant upwind terrain. Therefore, when considering the reproduction range of the terrain, it is necessary to determine the reproduction range according to the height of the flow field of interest, but it is necessary to further study the judgment criteria in the future.

This study investigates the influence of 3d-printed tube-like void for the use of part of pressure tube system on its response characteristics. The model used for the investigation models an urban area containing several buildings with geometrical scale of 1:500. The connections between the holes on building roofs and tube connectors are designed using a maze searching algorithm with extension, considering clearances between the tube-like voids as well as workability with 3D printer. The obtained tube-like voids are zigzag shape and the cross sections are not homogenous at their corners; however, the influence of such on dynamic pressure response characteristics is of minor and the use of such models is acceptable.

So far, this research group has conducted a wind tunnel experiment to measure the spread rate using a small fan to measure the effect of wind on the fire spread rate. However, since the problem remained in the air flow condition, we made a portable multiple wind tunnel device that can be transported and inexpensive.

In this study, we emphasized durability and transportability to improve the problems of prototypes and made a portable multiple wind tunnel using 3D CAD and 3D printer. By using a 3D printer, the contraction body, rectification body, and diffusion body became easily removable wind tunnel.

In the future, the shape of the contraction body will be improved, and the increase of the wind speed, the uniformity of the wind speed distribution, and the evaluation of the turbulence will be carried out.

The present experimental study aims to examine the flow condition of tornado genesis due to the occurrence of downdraft. We made 32 cases of laboratory experiment changing velocity and temperature of downdraft, environmental wind velocity and the arrangement of downdraft area and updraft area. The results show that the tornado-like vortices form in the preferred velocity conditions but the their rotation direction is opposite to that of presumption. In the cases that the updraft locates the diagonally upstream side of environmental wind, the rotating direction of the tornado-like vortices is changed by the change in flow condition and the counter-rotating vortex pair is also observed. Such facts show that the arrangement between the updraft and downdraft is important condition as well as the flow condition.

Radiosondes are used for aerological observations in environmental impact assessment of thermal power plants and geothermal power plants, but the development of alternative methods is expected due to their high cost and environmental load. In this study, we conducted parallel observations of UAVs and radiosondes, and examined the applicability of UAVs to aerological observations above 1000 m. As a result, it was shown that the wind direction, wind speed, and temperature measured by the UAV are almost the same as the observational results of the radiosonde.

In this research, we try a method to utilize the drone itself as a wind speed sensor without mounting a special observation device on the drone. First, a calibration test was conducted to utilize the drone as a wind speed sensor using a large wind tunnel facility. Next, we attempted to measure the wind turbine wake flow.

Most wind induced damage caused by strong winds occurs on the small buildings where detailed structural design is not required by the Building Standards Law. Wind tunnel experiment was carried out to measure the wind velocity around the roughness blocks for safety and reasonably designing such a small building. The vertical profiles of mean wind velocity and turbulence intensity around the roughness blocks were obtained from the time histories of the experimental data. Finally, the relationship between the proposed equations in the previous studies and the present experimental data was compared.

When improving urban ventilation within a focused urban block, it is necessary to consider the adverse effects on ventilation within the leeward area of focused urban block. In the Part 1 of this study, the influences on Quality; improvement of breathability within a focused urban block, and Load; increase of kinetic energy dissipation and decrease in kinetic energy transport to the leeward area, due to non-uniformity of building height, were quantitatively evaluated. By the non-uniformity of building height, while breathability evaluated by the kinetic energy exchange in the vertical direction increased by approximately 2.6 times, the kinetic energy transported to the leeward area decreased by approximately 10%.

In the Part 1, Quality; improvement of breathability within a forcused urban block, and Load; increase of kinetic energy dissipation and decrease in kinetic energy transport to the leeward area, due to non-uniformity of building height, were quantitatively evaluated. In this Part, simultaneous evaluation method of Quality and Load was proposed, and influence of non-uniformity of building height was evaluated. As a result, it was indicated that non-uniformity of building height of the high-density urban block in this study is a morphological change with high efficiency on kinetic energy exchange in the vertical direction.

Large-eddy simulations (LES) were performed to clarify the urban morphology that promotes high breathability and controls high wind speed at pedestrian-level. We performed LES on urban areas including a high-rise building and urban areas with non-uniform building heights, and following results were obtained.

1. Breathability increases around high-rise buildings due to the effect of advection in the urban area including a high-rise building. On the other hand, breathability increases in urban areas with non-uniform building heights due to increased effects of diffusion across the urban area.

2. Urban areas with non-uniform building heights promotes high breathability and controls high wind speed at pedestrian-level, making them superior to those including a high-rise building.

In recent years, with the development of computer techniques and the advent of high-performance computational resources, it has led to use large eddy simulation (LES) to predict flow fields around buildings. However, current LES methods still face some uncertainty due to the complexities of the theoretical model and flow fields around buildings. Thus, it is important to validate LES results by comparing them with field measurements or wind tunnel test results. We examined the accuracy of LES based on PIV measurements for a square-sectioned building model with an aspect ratio of 8. Comparison between LES and the PIV test results indicate that LES can accurately reproduce mean flow fields around buildings and second-order moment values for the horizontal plane even for very close to the ground (pedestrian-level).

Salt particles accelerate the corrosion of steel materials and, thus, it is important to clarify the mechanism of transportation and adhesion of salt particles for effective maintenance. In this study, flow field analysis and particle tracing analysis around rectangular cylinders were conducted by CFD to investigate the mechanism of transportation and adhesion of particles. The transportation process depended on the shape of a structure, which resulted in a unique distribution of the salt amount. Additionally, the authors studied a method of estimating the amount of adhesion based on the surface pressure of the structure. The results showed the possibility of estimating the distribution of adhesion from the fluctuating pressure coefficient and the spatial gradient of the time-averaged pressure coefficient on the rectangular surface.

In this study, aerodynamic performances of corner-cut rectangular cylinder (B/D = 1.5) and the effects of vortices on its galloping responses were experimentally investigated by providing different flow separation conditions with various corner types. The Strouhal numbers (St) of all corner-cut sections were higher than that of the rectangular section. However, the onset reduced wind velocities of the corner-cut sections increased although the 1/St decreased. This is probably because the influence of motion-induced vortices becomes higher as the Kármán vortex shedding is reduced.

Large-amplitude torsional aerodynamic vibrations are perhaps explained by the unsteady aerodynamic forces determined by the angle of attack and the time derivative of it in comparatively higher reduced wind velocity region. In this study, the above-mentioned aerodynamic forces as a function of angle of attack and the time derivative of it were obtained by measuring the aerodynamic forces during continuous rotation at a constant angular velocity on rectangular cylinders with a side ratio of B/D = 2 and 5, where torsional flutter occurs. Using these aerodynamic forces, the unsteady aerodynamic forces during torsional vibrations with various amplitudes in comparatively higher reduced wind velocity region were tried to explain. As a result, the flutter derivatives were expressed for B/D = 2, as well as B/D = 5 shown in the past. Furthermore, the unsteady aerodynamic forces were expressed not only the vibration frequency component which contributes to the work but also higher frequency components.

As the fundamental study for establishing an amplitude evaluation method for Rain-Wind-Induced-Vibration, the aerodynamic coefficients of a cylinder with a protrusion were measured. According to the results, the aerodynamic coefficients which were nondimensionalized by orthogonal wind speed towards the cylinder were corresponded when the Reynolds numbers which were calculated by inlet wind speed were the same. The aerodynamic coefficient which is used in the numerical simulation of RWIV should be measured in the condition of the same Reynolds number as real phenomena and without yawing angle.

In the case of the vehicle on the embankment-shaped structure moving from windless area into wind field, it was found that the wind pressure was different between the windward surface and the leeward surface. On the windward side, the maximum value is reached after entering the wind field, but on the leeward side, it is the minimum value after a while. In this study case, the influence of wind pressure due to the movement of the vehicle was not observed.

The objective of this research is to experimentally investigate the effects of the wind barrier, regarding the aerodynamic response of the bridge and the aerodynamic forces of the vehicle on the bridge. A box girder model with a width-to-height ratio of 9 is applied. The wind barrier is with a constant height and with a section of Straight-line Type (ST) and Curved-line Type (CT). The opening of the wind barrier was non-dimensionalized as Opening area Ratio (OR), the ratio of its opening area to its windward-surface area. Based on the results of the torsional 1DOF free vibration tests on the girder, the wind barrier of OR = 0% resulted in the aerodynamic instabilities of the girder, i.e., the vortex-induced vibration and torsional flutter, while increasing OR stabilized these aerodynamic instabilities. Based on the measurement of the aerodynamic forces on a simplified vehicle on the girder, enlarging OR increased the drag force coefficient (Cs) of the vehicle, whereas the wind barrier of OR = 50% still reduced Cs by about 50% compared with that without wind barrier.

In this study, the uplift loading tests of the joint were carried out for the metal roof deck by the layered roof repair method, and the degree of the increase strength in the case of wind-resistant reinforcement was evaluated. And, as a technique for quantitatively explaining the wind-resistant reinforcement effect to the user of the building, the fracture probability by the fragility function reflecting the test result was calculated.

In the case of installation on an existing building, the wind load of the photovoltaic panels acts on the fixed part of the roof at the same time as the normal wind load, but as a result of examining the simultaneity of the two loads, it was shown that the maximum value of both loads does not occur at the same time, and that it is sufficient to design a combination of the maximum value of the load on the roof surface and about 0.65 times the load on the panels.

Vertical fins attached to the wall of a building have been shown to occur peak wind force coefficients with absolute value exceeding 6.5 at the building edge and peak wind force coefficients with absolute values exceeding 3.5 at the general part of the building. From these results, it is possible that the mechanism of negative pressure occurrence is different because of differences in the vertical distribution of the wind force coefficients of the vertical fins at the building edges and in the general part of the building. Therefore, it is important to study the mechanism of wind load generation at each part for rational wind load evaluation. In this study, the mechanism of the peak wind force coefficients generated in the vertical fins of the general part was investigated associating with the LES based visualization. It was estimated that the reason for the absolute value of the minimum peak wind force coefficient to be larger in the middle and lower sections of the vertical fins in the general part was due to the generation of inverted conical vortices from the lower layers of the fin at the building edge.

The flow around a steel stack in the atmospheric boundary layer often reaches the post-critical Reynolds number region. It is impractical to reproduce the flow in this region by means of wind tunnel experiments due to the limitation of wind tunnel performance. If numerical wind tunnels can be developed to replace experiments with numerical simulations, it will be possible to significantly reduce costs and to study conditions that are difficult to achieve experimentally. As an initial step toward this goal, in this paper, numerical simulations are performed around a roughened and a plated three circular cylinders simulating a concentric stack. The drag coefficients of the cylinders were calculated from the obtained results and compared with the experimental results to confirm that the drag coefficients agreed with the experimental results with sufficient accuracy.