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Atsushi Yamaguchi, Takeshi Ishihara
Pages
85-86
Published: 2017
Released on J-STAGE: June 15, 2017
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A gust forecasting model by based on ARX model which uses numerical weather prediction and on-site measurement as inputs, was proposed and the model parameters were estimated by using non-parametric regression with forgetting factor. By using dynamically adaptive model, the prediction accuracy was improved compared to the conventional static MOS model. It was also shown that the prediction accuracy of maximum gust improves by utilizing the model ensemble method which uses two different numerical weather predictions. The predictability of the gust event with the maximum wind speed larger than 15ms, was evaluated by using ROC curve and AUC and it was shown that proposed method improves predictability of gust wind event.
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Takeshi Ishihara, Atsushi YAMAGUCHI, Jay Prakash GOIT, Jun TANEMOTO
Pages
87-88
Published: 2017
Released on J-STAGE: June 15, 2017
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Vertical and horizontal profiles of mean wind speed obtained from
numerical weather simulation are validated by using 3D Scanning Lidar
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Yusuke Nishimuta, Hiromichi Shirato, Kyohei Noguchi
Pages
89-90
Published: 2017
Released on J-STAGE: June 15, 2017
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Overturning accidents of cars caused by strong crosswind have still occurred in Japan. Instantaneous strong crosswind has a heavy influence on overturning of running cars. Therefore, it is necessary to provide safe road transportation by predicting maximum instantaneous wind speed and giving warnings to drivers in advance. In this paper, the authors predicted maximum instantaneous wind speed using a peak factor obtained by observed data and a relation between mean wind speed and standard deviation on the basis of steady flow by computational fluid dynamics. As a result, maximum instantaneous wind speed predicted by computational fluid dynamics showed good agreement with observed data in a high wind speed range which has direct effects on the stability of running cars. The result shows that it is possible to make a simple prediction of maximum instantaneous wind speed using steady flow by computational fluid dynamics.
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Yasuo HATTORI, Keisuke NAKAO, Hitoshi SUTO, Hiromaru HIRAKUCHI, Yuzuru ...
Pages
91-92
Published: 2017
Released on J-STAGE: June 15, 2017
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We discuss behavior of gust factor in the real atmospheric surface layer predicted by using large-eddy simulations with a numerical weather prediction model in detail. The grid resolutions are set at 5.6m. The relationship between gust factor and averaging time corresponded to the Durst curve. The relationship strongly depended on the existance of -2/3 slope region in power spectra of wind speed fluctuation, and also coherence structures, such as streaky structures.
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Tsuyoshi Kurita, Takayuki Komi
Pages
93-94
Published: 2017
Released on J-STAGE: June 15, 2017
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We observed the wind above urban area on a high-rise building with a height of 125m in Tokyo. In this paper, we investigated the characteristics of wind turbulence using observation results of two seasonal winds and three typhoons.
(1) The turbulence intensity decreased with increasing mean wind speed, and it was close to the recommendations value (0.138) of roughness category III when wind speed exceeded 15 m/s.
(2) The gust factor showed a tendency to be proportional to the turbulence intensity. The relation between the evaluation time and the gust factor showed a value close to the Durst curve at the time of the seasonal wind and it was slightly larger at typhoon.
(3) The peak factor calculated from the relationship between the gust factor and the turbulence intensity was about 2.5.
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Hiroshi Hasebe, Nao Fukaya, Takashi Nomura
Pages
95-96
Published: 2017
Released on J-STAGE: June 15, 2017
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Characteristics of the nature wind based on wind observation have been carried out so far. Among them, wind speed frequency distribution and maximum instantaneous wind speed were focused on. On the other hand, few studies focused on wind direction characteristics compared with those studies. Authors set an ultrasonic anemometer on the roof of our university building and conducted wind observation. Therefore, in this study, we focused on wind direction observed by ultrasonic anemometer and investigated wind direction characteristics according to averaging times. As a result, although it is limited data of one month, it turned out that there is clear difference in the wind roses of the instantaneous wind direction and the 10 minute average wind direction.
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(Part 1)Development of Wind Environmental Map
Taichi Shirasawa, Yoshida Masako, Kunio Fujii, Ryuichiro Yoshie
Pages
97-98
Published: 2017
Released on J-STAGE: June 15, 2017
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It is difficult for residents to measure wind speed in their everyday lives. Therefore, it is thought that few residents grasp the wind environment of their town.
The purpose of this study is to develop the wind environmental map based on the wind measurement by residents to understand the wind environment of their town and share information on it. We conducted the investigation on the wind environment by community participation in Musashikosugi area using pocket type anemometer. The wind environmental map was created based on the measured wind speed, impressions and phenomena reported by the residents.
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(Part 2)Proposal of Wind Force Scale based on free description by local residents
Masako Yoshida, Taichi Shirasawa, Kunio Fujii, Ryuichiro Yoshie
Pages
99-100
Published: 2017
Released on J-STAGE: June 15, 2017
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The purpose of this paper is to propose a new wind force scale based on free descriptions by local residents to examine the relation between wind speed and the impressions or phenomena caused by the wind.
Firstly, the free descriptions were categorized into 6 groups such as “tree”, “hat, hair, clothes”, “umbrella”, and so on. Next, for each group, the characteristic words in the free descriptions were extracted by Text Mining. A new wind force scale for each group was proposed based on the sentences including the extracted characteristic words.
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Comparison between Tokyo and Sendai in the 2050s
Miguel Yamamoto, Masataka Kasai, Tsubasa Okaze, Kazumasa Hanaoka, Akas ...
Pages
101-102
Published: 2017
Released on J-STAGE: June 15, 2017
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This study aims to quantify the spatial distribution of outdoor heatstroke risk in Tokyo and Sendai during the summer season in the 2050s. To predict the spatial distribution of the WBGT, mesoscale meteorological simulations were performed by the Weather Research and Forecasting model (WRF) using pseudo global warming method. In the prediction results, the daily maximum Wet-Bulb Globe Temperature (WBGT) increased in the whole area, and the number of people transported by ambulance due to heatstroke increased about 2.4 times in 2050s compared with 2000s in both Tokyo and Sendai.
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Shinji Yoshida
Pages
103-104
Published: 2017
Released on J-STAGE: June 15, 2017
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In this study, the applicability limit of mitigation method of airflow on thermal environment was investigated using a human thermoregulation model. The two-node cylindrical human thermoregulation model was used in the present analysis. The applicability limit of mitigation method of airflow was evaluated from the results of physiological responses 60 minutes after the beginning of the calculation. Through the investigation, it has been found that the applicability limits were seen at the environment where values of the sum of the sensible and the latent heat flow from the environment to the human body are negative at the high operative temperature and the high relative humidity.
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Effect of model scale factor is on the non-dimensional concentration
Takumi Tachibana, Ryuichiro YOSHIE, Koichi MIYASHITA, Ryoji SASAKI
Pages
105-106
Published: 2017
Released on J-STAGE: June 15, 2017
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In the prediction of the concentration of pollutants by wind tunnel experiments, in the case where a wide range of contaminant diffusion is targeted, there is no choice but to reduce the scaling factor of the model from the limitation of the size of the wind tunnel, so that there is a possibility that the accuracy of the experiment will decrease .
Therefore, in this study, we conducted a wind tunnel experiment in which the scale ratio of the model was changed to 1/300, 1/600, 1/1000, and investigated the influence of the model scale ratio on the non-dimensional concentration.
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Part1 PIV Measurements of Outdoor Air Flow around Two Adjacent Building Models
Shin-ichi Akabayashi, Yuki Arinami
Pages
107-108
Published: 2017
Released on J-STAGE: June 15, 2017
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Outdoor airflow distribution around buildings largely differs depending on regional wind direction and wind velocity, building shape, surrounding conditions around the building.
In this study, airflow visualization and Particle Image Velocimetry(PIV) measurement for models combining middle and high rise buildings using large boundary layer wind tunnel. In addition, spatial distributions of Gust Factor, which is an important indicator for evaluating the wind environment in urban areas, are calculated from the PIV measurement results and grasp the characteristics of the outdoor airflow around the high-rise building.
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Yuki Arinami, Shin-ichi Akabayashi
Pages
109-110
Published: 2017
Released on J-STAGE: June 15, 2017
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The driving force behind natural cross-ventilation is outdoor wind. The indoor airflow distribution and flow rate under cross-ventilation vary greatly because the direction and velocity of wind changes constantly. Thus, cross-ventilation is said to be an unsteady fluid phenomena. Recently, unsteady fluid phenomena have been analyzed by using large-eddy simulation. In this study, a new evaluation method that considers flow fluctuation for natural cross-ventilation is proposed. The evaluation results for the performance of this unsteady natural cross-ventilation model are reported. Consequently, in Cases 2 to 4 wherein no ventilation occurs in a time-averaged flow field, there are unsteady ventilation phenomena. In cases 2 to 4, the effective ventilation rates under unsteady flow are approximately 10% to 20% of those in Case1.
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Masataka Kasai, Tsubasa Okaze, Akashi Mochida
Pages
111-112
Published: 2017
Released on J-STAGE: June 15, 2017
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This study aims to apply artificially generated turbulent fluctuations of wind velocity and air temperature as an inflow boundary condition for a large-eddy simulation of a non-isothermal flow around a building. The stratification condition of the flow field was a weak unstable situation. The artificial turbulent fluctuations generated by our method satisfy not only the prescribed profiles for the turbulent fluxes of the momentum and the temperature but also the prescribed spatial and time correlations. The mean wind velocity and the mean temperature predicted from LES agreed well with the experimental results.
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Yuto Sakuma, Tetsuro Tamura, Hisaaki Ozaki
Pages
113-114
Published: 2017
Released on J-STAGE: June 15, 2017
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Wind flow and dispersion characteristics are sensitively changed by advective effects based on the wind flows above and within the urban canopy layers. For the simulation, we use LES simulation and employ the two pattern of the model such as 0degree case (larger aspect area of upwind side) and 90degree case (smaller aspect area of upwind side). From the 0degree simulation (larger aspect area), we found special distinctive phenomena inside the canopy area such as the large scale span wise flow switching from side to side. Those large scale flow is universally and randomly occurred inside the canopy area. In this study, we focus on the trigger of the those characteristics and structure using some kinds of visualization technic, and we reviled the occurrence of flow direction change. At the same time, we consider the dispersion phenomenon. Basically those dispersion characteristics depends on the switching flow but when the both side of switching flow are impinging from the each side of dispersion source, concentration stagnate inside of the canopy and exhaust from upward. This is the mechanism of the suddenly high concentration at back ward blocks.
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Yui Murayama, Igarashi Kenji, Masaki Nemoto, Yoshihide Tominaga
Pages
115-116
Published: 2017
Released on J-STAGE: June 15, 2017
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This paper reports the results of a cold wind tunnel experiment using artificial snow and a fundamental CFD analysis for investigating the applicability of erosion/deposition models in CFD to the roof snow prediction. In the results of the wind tunnel tests, the significant snow erosion was observed not only upwind resion of the ridge but also downwind of the roof for all roof pitches tested. Furthermore, in the results of CFD which represents the wind tunnel experiment, it was confirmend that the resulted snow depths correspond well with the distribution of friction velocity at the upwind side, but not at the downwind side.
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Tsubasa Okaze, Hirofumi Niiya, Kouichi Nishimura
Pages
117-118
Published: 2017
Released on J-STAGE: June 15, 2017
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This study aimed to propose a drifting snow model combined with a large-eddy simulation for flow field and a lagrangian model to predict particle motion. Aerodynamic entrainment, rebound and splash process of snow particle on snow surface were included. Then, a priori simulation within a boundary layer under weak wind speed condition was conducted. The streaky regions of high drifting-snow-density were formed near the snow surface along with the streamwise direction.
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Kota Enoki
Pages
119-120
Published: 2017
Released on J-STAGE: June 15, 2017
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In Japan, flat sites suitable for wind power generation are limited, and high accuracy of the wind resource assessment in the mountain area is needed for the feasibility of power generation projects. In the mountain area, it is necessary to consider the complexity of the land cover as well as that of the topography. With the progress of satellite observation technology in recent years, it is becoming possible to measure the elevation that contains information of the land cover height for all over the world at high resolution. In this study, the estimation method of the height of surface covering based on the satellite data called AW3D30 is examined and the simple examples applied to numerical analysis is shown.
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Koichi Watanabe, Sho Fukutomi, Yuji Ohya
Pages
121-122
Published: 2017
Released on J-STAGE: June 15, 2017
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A new type of solar tower was developed through laboratory experiments and numerical analyses. When solar radiation heats the ground through the glass roof, ascending warm air is guided to the center and into the tower. A solar tower that can generate electricity using a simple structure that enables easy and less costly maintenance has considerable advantages. Furthermore, the tower can also generate electricity using an upper wind over the tower at night. Namely, the tower is a hybrid generation system.
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Eriko Tomokiyo, Kato Kanji, Maeda Junji
Pages
123-124
Published: 2017
Released on J-STAGE: June 15, 2017
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It is important to predict a damage risk in an area due to gusty winds in order to make disaster measures of local government and to calculate a rate of a nonlife insurance premium. In this paper, we tried to predict a damaged area of buildings using building densities and the high wind damage scale by the tornado that occurred in Nobeoka, Miyazaki in 2006. Then we compared the actual building damage and the predicted one. Since there were many non-damaged building in an area where smaller wind blew, actual occurrence rate of damage building was not coincident with probability density used to predict. Therefore, large damaged area of buildings was predicted in an area where building damage hardly occurred in reality. However, the predicted building damage and the actual one corresponded in an area where stronger winds blew.
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Koji Sassa, Misa Komatsubara
Pages
125-126
Published: 2017
Released on J-STAGE: June 15, 2017
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Non-supercell tornadoes occur on the gust front between cold outflow around cumulonimbus and environmental flow. Because such tornadoes cannot be caught by radar before their generation, we need to know the environment of airflow around tornadogenesis. We tried to reproduce tornado-like vortex in the situation that cold outflow intrudes into environmental flow. As the results, we found that tornado-like vortex was stably generated when the cold outflow slightly faster than the environmental flow. The circulation of tornado-like vortex increased in proportion to the velocities of both flow.
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Meizhi Liu, Masahiro Matsui
Pages
127-128
Published: 2017
Released on J-STAGE: June 15, 2017
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Tornado is one of the factors of strong wind damage of buildings in Japan. In order to reduce the damage of tornado, it is necessary to investigate what property the tornado flow has. This study aims to clarify the wind velocity distribution of tornado vortex by using the tornado-like flow simulator, obtaining the flow velocity of the flow field by PIV. As a result, there was a maximum value of the wind speed in the vicinity of the ground. In that region the variation in the wind speed was high. According to the radial distance from the center , the tangential wind speeds increased to the maximum value of the wind speed and decreased from there for each height. A bimodal distribution was observed at a part of the height. Furthermore, radial distributions of tangential wind speeds and vorticities were similar to those of Burgers vortex.
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Seiji Nakato
Pages
129-130
Published: 2017
Released on J-STAGE: June 15, 2017
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Measurement of aerodynamic forces on rectangular cylinder supported as cantilever beam with load cell was conducted. Drag coefficient is almost same to that of supporting as a simple beam with two-component force meter. As for the fluctuating lift coefficient, when B / D = 1, it is a about half value of measurement with 2-component force meter. With B/D= 3, fluctuating lift coefficients were almost same in some wind speed range. In the case of model has two cross sections of B/D=1,3 and the free end side is B/D=3, the fluctuating lift coefficient becomes larger.
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Mai Shimonishi, Ikuma Tsukamae, Hiromichi Shirato
Pages
131-132
Published: 2017
Released on J-STAGE: June 15, 2017
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In turbulence flow, the correlation of surface pressure and gust response factor along span-wise direction near the leading edge of a rectangular prism is higher than the correlation of them in approaching flow. It is advocated that this increase in the correlation is affected by vortex shedding or two-dimensional flow structure of separation bubble. In this study, the flow structure around the rectangular prism with chord/depth ratio of 8.0 which is the cross section of flow completely reattachment type in smooth flow and turbulence flow are visualized and captured by PIV (Particle Image Velocimetry) analysis. The flow fields are decomposed by DMD (Dynamic Mode Decomposition) thus discussed the structure of flow including separating shear layer and the mechanism of increase in the correlation along span-wise direction. The results imply the nonuniformity of the momentary reattachment point along span-wise direction in turbulence flow and the characteristic flow derived from the structure of separation bubble contribute to the increase of span-wise correlation.
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KAZUTOSHI MATSUDA, KUSUO KATO, KOUKI ARISE, HAJIME ISHII
Pages
133-134
Published: 2017
Released on J-STAGE: June 15, 2017
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In this study, smoke flow visualizations were performed for ratios of B/D=0.5?2.0 in order to find out the relation between side ratios of rectangular cross sections and secondary vortices at trailing edge in motion-induced vortex excitation. The smoke flow visualizations around the model during oscillating condition were conducted in a small-sized wind tunnel at Kyushu Institute of Technology. Experimental Reynolds number was Re=VD/v=1.6×10
3. For the forced-oscillating amplitude η, the non-dimensional double amplitudes were set as 2η/D=0.02-0.15.
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Yoshiyuki ONO, Tetsuro TAMURA
Pages
135-136
Published: 2017
Released on J-STAGE: June 15, 2017
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The objective of this paper is to clarify the pressure characteristics of a square cylinder when wind direction is changed by using LES. Based on the computed results,the large peak suctions are recognized near the corners of a square cylinder in some cases. The flow characteristics associated with the large peak suction are investigated.In the case of the gradually change of the wind direction, the flow separation and reattachment near the frontal corners change to formation of separated shear layer in the wake region as observed in the flow patterns around a square cylinder. On the other hand, when wind direction largely changes, the large peak suctions are caused by the difference of the timing between flow characteristics near the square cylinder and approaching flow.
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Minoru Noda, Kengo Okimoto, Fumiaki Nagao, Fujio Ishida, Akinori Tsuji
Pages
137-138
Published: 2017
Released on J-STAGE: June 15, 2017
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Authors developed a multi-fan and multi-vane type tornado simulator equipped with a moving belt to reproduce the tornado-like flow in the moving state. As results of 3D-PIV measurement, the tornado-like flow in the moving state could be reproduced as expected, and as a result of improving the operation accuracy of the device, it was clarified that this tornado simulator could reproduce the multi cell type vortex whose control was very difficult on the previous simulator. In this paper, the structure of the newly developed tornado simulator is introduced and the effect of the given swirl ratio and the moving speed of moving belt on the tornado-like flow field are reported.
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TAKASHI SHIDA, TAKESHI KUBOTA, AKIHIRO HONDA
Pages
139-140
Published: 2017
Released on J-STAGE: June 15, 2017
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Wind tunnel tests of ‘Rotational Flow Wind Turbine’, 0.94 m in diameter, and 0.847m in height, was conducted. The turbine has eight blades, and two kinds of blade width was tested.
The torque coefficient at the tip speed ratio of 0.2 was above 0.25, and maximum power coefficient shows the value of 0.07 at the tip speed of 0.38.
Additionally, a vane-type hydraulic pump, which was directly connected to the wind turbine, was certificated to be able to pump up the water above 5.7m height.
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Kyohei Noguchi, Haruka Ii, Hiromichi Shirato, Tomomi Yagi
Pages
141-142
Published: 2017
Released on J-STAGE: June 15, 2017
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It is necessary to evaluate the salt amount in each member of a bridge for effective maintenance. The dry gauze method is authorized well in Japan, while its collecting efficiency of salt particles has not sufficiently been clarified. The authors evaluated air flows around a device of the dry gauze method by wind tunnel experiments. It turned out that the flow pattern around the device depended on approaching wind speeds and wind directions. This implies that the collecting efficiency also depends on wind conditions. Additional experiments, CFD calculations, and on-site observations will be conducted in the future.
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Kento Matsui, Takashi Maruyama, Hiroaki Nishimura, Hiroshi Noda, Kazuy ...
Pages
143-144
Published: 2017
Released on J-STAGE: June 15, 2017
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In most cases, failures of buildings in strong wind, e.g. typhoon or tornado, are caused by flying debris. In order to reduce the damage to buildings by flying debris, clarifying aerodynamic characteristics of flying debris and evaluating of motion of debris are needed. In this study, the system that measures the aerodynamic characteristics of flying debris directly was developed. A sensor unit assembled with pressure sensors and three axis accelerometer was built in the rectangular shaped model. The model was dropped and the pressure and the acceleration were measured. At the same time, the motion of the model was captured by taking movies with cameras and conducting image analysis.
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Hideyuki Tanaka, Kazuo Ohtake, Naoko Konno
Pages
145-146
Published: 2017
Released on J-STAGE: June 15, 2017
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The prediction accuracy of CFD has been reported by many studies by comparing the results of wind force coefficients derived from wind tunnel tests. The authors have been investigating the prediction accuracy of their own code for LES (Large-eddy simulation) on tall buildings with various configurations to determine its usefulness in wind force evaluation by CFD. In this study, to clarify the effects of Immersed Boundary Method on LES prediction accuracy, we carried out numerical simulations for a square cylinder placed in turbulent boundary layer flow, and compared the results with those of wind tunnel tests.
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PHAM VAN PHUC, Tsuyoshi Nozu, Hirotoshi Kikuchi, Kazuki Hibi, Yukio Ta ...
Pages
147-148
Published: 2017
Released on J-STAGE: June 15, 2017
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Numerical simulations using two types of subgrid-scale (SGS) models, Standard Smagorinsky model (SM model) and Coherent Structure Smagorinsky model (CSM model) for Large Eddy Simulation (LES) with different Courant numbers, were carried in a low-turbulence uniform flow for the rectangular and setback buildings. The CSM model gave more accurate results than the SM model for the setback building that has been observed on the sidewall of building with large negative pressures due to the strong coupling of the vortices. The large negative pressure coefficients are also changed by the Courant numbers.
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Takashi Nomura, Toshiki Kobayashi
Pages
149-150
Published: 2017
Released on J-STAGE: June 15, 2017
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Although drones are widely used for a variety of applications, the limited capacity of loadable battery is a serious limitation. In order to develop a tool to obtain paths or control methods to minimize battery consumption, an analytical model of drone is investigated by considering thrusts, torques from the rotors as well as the aerodynamics forces or wind. A quadcopter is simplified as a rigid square plate and rpm of each rotor is given to generate thrust and torque. The equations of motion of the rigid body is solved by the Newmark-b method. Some basic drone motions are obtained by investigating the time histories of the rpms of the four rotors.
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Part 2: Simulation of Internal Pressures Considering Translation Effect of Tornado-like Wind
Hitomitsu Kikitsu, Yasuo Okuda
Pages
151-152
Published: 2017
Released on J-STAGE: June 15, 2017
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In this study, numerical simulation of internal pressure is carried out by applying external wind pressure data obtained from wind pressure experiments to the past proposed model. The purpose of this simulation is to understand mechanism of the internal pressure generation under the translation effect of tornado-like wind. The numerical result shows that the past model can properly simulate internal pressure characteristics obtained from the experiments. Next, the way to estimate internal pressure characteristics under the translation effect is studied by associating translation speed with additional coefficient composing of the past model.
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Yuki Takadate, Yasushi Uematsu
Pages
153-154
Published: 2017
Released on J-STAGE: June 15, 2017
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The present paper discusses the flow field around a long-span flat roof, based on a computational fluid dynamics (CFD) simulation. The simulation is conducted by using uniform flow because a roof vibration will be occurred in low turbulence flow. First, distributions of mean and RMS fluctuating wind pressure coefficient are computed and compared with the previous experimental data. Then, wind velocity, vorticity and phase lag are investigated in order to make clear the mechanisms of separated and reattached flow around the roof.
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Hiromu Honda, Tsuyoshi KURITA, Akihito YOSHIDA
Pages
155-156
Published: 2017
Released on J-STAGE: June 15, 2017
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This paper describes characteristic of wind pressure for screen standing on rooftop. The blindfold screen is often attached to the outside perimeter of building. In this study, wind tunnel tests were performed to investigate difference in peak wind force coefficient obtained from backside pressure of the screen and rooftop pressure, and the characteristics of backside pressure of the screen. As a result, we experimentally clarified difference occurs in the peak wind force coefficients obtained from backside pressure of the screen and rooftop pressure, because backside pressure of the screen changes to vertical direction depending on wind direction. However, there was no change in the value of the maximum peak wind force coefficients in the all wind direction.
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Maiko Arai, Hidenori Kawai, Tetsuro Tamura, Takayuki Yamaguchi, Keisuk ...
Pages
157-158
Published: 2017
Released on J-STAGE: June 15, 2017
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It is required to clarify the effect of the turbulence field formed by surrounding buildings for wind load estimation of high rise building. Also, its wind load can become high due to surrounding pressure field. This study clarifies the influence of the turbulence field formed by surrounding buildings and pressure field around claddings by analyzing high-rise building located in high-rise urban area. As a result, flows separated from windward buildings flows come into the space surrounded by other buildings and the negative pressure is intensified on the north-west upwind point of 23
rd floor.
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Hidenori Kawai, Tetsuro TAMURA, Hiroakira NUKAGA
Pages
159-160
Published: 2017
Released on J-STAGE: June 15, 2017
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For estimation of wind load by CFD, number of inflow wind direction, ensemble number, and integration time increase calculation loads. Thus, practical method is necessary for CFD. This study clarifies the accuracy of wind pressure by LES at reduced grid number. As a result, peak wind pressure coefficient underestimated at the lower part, corner and roof of high rise building, but the tendency of local wind pressure and force on target building is reproduced in the case at reduced grid number.
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Koji KONDO, Tetsuro TAMURA, Hidenori KAWAI, Takamasa HASAMA, Yoshiaki ...
Pages
161-162
Published: 2017
Released on J-STAGE: June 15, 2017
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LES was carried out to simulate the wind pressure acting on the high-rise building wall surface in the middle class and the high-rise city area on the complex terrain. The computed results were compared with the wind tunnel test results to confirm their applicability. As a result, the following things were confirmed. The flow field around the target building was influenced by the neighboring high-rise buildings. As for the wind pressure coefficients, the computed results coincided with the wind tunnel test results. The error of the computed results for the wind tunnel test results was almost in the range of 20%.
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tetsu yonekura, Yukio tamura, Akihito yosida, Wonsul Kim
Pages
163-164
Published: 2017
Released on J-STAGE: June 15, 2017
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Unique buildings with that are different from conventional ones are being constructed in recent years, and studies for rational construction have already been done. However, wind response characteristics of s Tall Buildings having various cross sectional shapes are not clear.
In this study,we conducted an aerodynamic vibration experiment to investigate the wind response characteristics of a Tall Buildings with the purpose of clarifying the change of the influence when changing the shape
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Yoshiki Watanabe, Akihito Yoshida, Tetsu Yonekura
Pages
165-166
Published: 2017
Released on J-STAGE: June 15, 2017
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Most of the communication towers mainly have a truss structure steel tower that uses mountain-shaped steel, steel pipe, etc., excellent in weight and strength. However, due to the Landscape Law promulgated in 2004, the number of scenery towers using a structure type other than the truss structure considered in the landscape is increasing.
The scenery steel tower is lightweight and has a large aspect ratio, and it is necessary to evaluate the wind performance evaluation to measure the data which is the basis of the wind resistance design.
In this research, in order to confirm the occurrence of aerodynamically unstable vibration, using the model of the four pillars of the next generation type communication tower, from the air current of the ground surface roughness classification Ⅱ, Ⅲ, Ⅳ, aerodynamic vibration experiment .
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Yong Chul Kim, Yukio Tamura
Pages
167-168
Published: 2017
Released on J-STAGE: June 15, 2017
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In this study, response characteristics of solar wing structures were investigated. From the results, it was found that responses are largely dependent on the panel shapes, and the large fluctuating responses shown in low wind speed range were considered to be the resonant phenomenon.
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Hiromasa Kawai
Pages
169-170
Published: 2017
Released on J-STAGE: June 15, 2017
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Galloping of a rectangular cylinder with a side ratio B/D larger than 1.5 where D is a projection depth and B is an along wind width starts around a resonant velocity of Karman vortex shedding. The amplitude is affected little by a structural damping, and it increases linearly with the velocity. It is tried to clarify in this paper what physical law is possible to explain the experimental results for the galloping. As the results, the non-dimensional frequency defined by the velocity and the vibrating frequency and the projection depth is constant during the galloping. That means a so-called universal Strouhal number can be applicable to the galloping.
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Yuta Sasaki, Tomomi Yagi, Takahiro Komatsu, Hisato Matsumiya, Takashi ...
Pages
171-172
Published: 2017
Released on J-STAGE: June 15, 2017
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In general, aerodynamic instabilities of bluff bodies are investigated in the very small amplitude region. In this study, a rectangular cylinder with a side ratio of five is used to investigate its large amplitude vibrations under three DOF condition. To understand the responses, the time history analyses are applied by using two kinds of aerodynamic forces: quasi-steady aerodynamic force and the aerodynamic force to which the torsional velocity term is virtually added. Then, the large amplitude torsional vibrations can be divided into the two following phenomena. One is coupled 2DOF large amplitude vibration caused by the torsional vibration, and the other is coupled 2DOF vibration which can be explained by quasi-steady theory.
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Hisato Matsumiya, Takashi Nishihara, Tomomi Yagi
Pages
173-174
Published: 2017
Released on J-STAGE: June 15, 2017
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In this study, to compare the galloping suppression effect depending on rotational clamps arrangement of loose spacers, we performed wind tunnel tests using sector models of four-bundled conductors. When the ice accretes in the conductor in the assumed wind direction, the four-bundled conductors with one-sided loose spacers are more effective than those with diagonal loose spacers. However, when ice accretes in the opposite wind direction in which two rotatable sub-conductors are placed at the downwind side, have a tendency to encourage galloping more than those without an anti-galloping device. In contrast, the diagonal loose spacers provide a suppression effect regardless of the wind direction. These differences are caused by the aerodynamic moment acting on the entire four-bundled conductor and depends on the arrangement of the rotatable sub-conductors.
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Yishan Yuan, Tomomi Yagi, Satoshi Ogawa, Ippei Sakaki, Hiromichi Shir ...
Pages
175-176
Published: 2017
Released on J-STAGE: June 15, 2017
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In this study, wake-induced vibrations of parallel cables and vibration control by spiral protuberances were investigated. From free vibration tests and flutter analyses, the mechanisms of wake-induced vibrations are clarified. By comparing responses obtained from time history response analysis based on quasi-stationary aerodynamics and flutter analysis, the response characteristics of the wake-induced vibration are clarified. Furthermore, the vibration effect and the aerodynamic characteristics will be discussed using cable with spiral protuberances expected to be applied as countermeasure against wake vibration. It is clarified that wake-induced vibrations are related to Karman vortex.
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Kichiro Kimura, Takahiro Ishii, Kosuke Sato, Tetsuya Yanagihara, Katsu ...
Pages
177-178
Published: 2017
Released on J-STAGE: June 15, 2017
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Dry Inclined Cable Galloping may occur with long stay cables of cable stayed bridges, and similar response may occur with general circular cross section members. In order to clarify its characteristics, a series of wind tunnel tests was conducted with an inclined circular cylinder model of small aspect ratio. Reproducibility was generally good, and response was observed around 9m/s (Re=1.6×10
5), it decreased at a little higher wind speed, and large amplitude response was observed at higher wind speed. Aerodynamic coefficients were measured with respect to the tests, and response analysis using quasi-steady aerodynamic forces was discussed. As a result, it was shown that the wind-induced response may possibly be caused by unsteady aerodynamic forces at nondimensional wind speed larger than 100.
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JIAQI WANG, TOMOMI YAGI, JUN USHIODA, NAOKI NAGAMOTO, HIROYUKI UCHIBOR ...
Pages
179-180
Published: 2017
Released on J-STAGE: June 15, 2017
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In order to investigate the effects of side wall openings on the aerodynamic performance of box girder, vertical free vibration tests were carried out in the wind tunnel. The openings’ effects are discussed for both single girder situation and parallel girders situation, by using two butterfly web girders with side ratio 3.24.
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Takumi Kodera, Hiroshi Katsuchi, Hitoshi Yamada, Shigeki Kusuhara
Pages
181-182
Published: 2017
Released on J-STAGE: June 15, 2017
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Minami-bisan Seto Bridge is a truss-stiffened suspension bridge. Its road deck has open grating in order to satisfy the aerodynamic stability. Recently, due to maintenance work, closure of the open grating is needed. In this study, aerodynamic stability of the girder with open grating closed is studied.
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Dongming Zhang, Kohei Wada, Hiromichi Shirato
Pages
183-184
Published: 2017
Released on J-STAGE: June 15, 2017
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Safety assessment is conducted considering the traffic. The vehicles in the traffic are divided into five vehicle types and simulated by five vehicle models. For each vehicle model, representative parameters are assigned, during which the side force coefficient and vehicle weight are generated randomly following properly defined probability distributions. Then traffic volume of 10000 vehicles with the given vehicle proportions of different vehicle types in reality is applied to calculate the overturning probability of the traffic. With this method, the effect of the vehicle proportion and vehicle speed on overturning probability of the traffic is investigated. In addition, the overturning probability of current highway traffic regulation rule is also studied. On the other hand, on-board pre-warning system is realized with a combination of the Characteristic Wind Curves, short-term wind velocity and direction prediction and risk analysis. For a given allowed overturning probability of the vehicle and considering the real-time observations of wind velocity and direction, the permitted vehicle speed is identified by this system.
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