Hiromasa Kawai

Local peak pressure and conical vortex on building

Abstract Characteristics and cause of local peak suction are discussed through a relation with the conical vortex. The peak suction is induced by the large and strong conical vortex formed on the roof and the wall when the gust attacks a building instantly from a particular direction in any mean wind directions. The large-scale gust is responsible for the formation of the vortex and the occurrence of the peak suction, because the development of the strong vortex takes time at least when the fluid particle travels a distance 4–5 times the roof size. The modification of the edge is very effective to reduce the peak suction, as it controls effectively the separation of the shear layer. When the eaves of the flat roof are recessed by 1 10 of the height of the building, the peak suction can be reduced to 2 3 of that on the roof without the recession.

On The Institution of The General Corporation Japan Association for Wind Engineering

平成 22年 5月,一般社団法人日本風工学会が設立され, 日本風工学会の全ての財産および業務が一般社団法人日 本風工学会に引き継がれました。このような学会の節目 となる大切な時期に会長に選出されたことはまことに名 誉であり,会員の皆様には心から感謝するとともに,身 の引き締まる思いです。初代会長の石崎先生から数えて 9 代目の会長になりますが,これまでの 8 人の会長と比 較して,浅学非才の私に,この重要な時期の会長職が務 めるかどうか,不安な気持ちで一杯ですが,皆様方のご 支持を真摯に受け止め,会長として精一杯務めさせてい ただこうと思っていますので,ご鞭撻とご協力をよろし くお願いします。 ところで,法人化は日本風工学会の長年の夢でした。 1976 年に「風工学に関心のある研究者の組織」として石 崎,伊藤,加藤,白石の 4 先生の連名によって発足した 日本風工学会は 1982 年に「日本風工学会」として名称を 変更するとともに,研究者のみならず風工学に関心のあ る方々の組織として学会活動を開始しましたが,その当 時から学会の法人化は最重要課題の一つとして絶えず議 論をされていました。当時は法人化の壁は高く,会員数 500 名,年間予算が 1000 万円足らずの小さい学会が法人 となることは至難の技でしたが,それでも法人化を目指 して,諸先輩方が規約を整え,基本財産を蓄積するなど 多大な努力を重ねてきました。法人化の話は,理事会, 評議員会,総会などで度々論じられてきましたが,風工 学会を法人として維持することは負担が重すぎる,とい うことで見送られてきました。法人化するにあたっての 詳しい経過は,本誌 1 月号に藤野前会長が述べているの で省略しますが,風が変わったのは平成 20 年に「一般社 河井宏允*

A Report on Wind Disasters Caused by Sever Local Storms from June to July in 2001

This report presents damages of houses and other structures caused by severe local storms which occurred on June 27, 2001 at Ichinomiya-shi in Aichi prefecture, on June 29, 2001 at Hokuryu-cho in Hokkaido prefecture, and on July 17, 2001 at Echigawa-cho in Shiga prefecture. According to the field studies, the damaged houses are distributed in a long and narrow region with 7-12km length and 200-600m width which correspond to P2 scale. The strength of the storms is estimated as F2 by the damage of houses. The damage of the roofing and roof systems are conspicuous. From the weather condition of each disaster illustrated by weather charts and images of GMS-5, the storms are caused by a local unstable atmospheric condition brought by a developing cumulonimbus cloud.

Characteristics of static pressure on the ground

Abstract When wind pressures on a building in natural wind are estimated, a static pressure measured with a manhole, a Pitot static tube, or a static tube of the disk type, has been used as the reference pressure. However, there are a few studies on the detailed characteristics of the static pressure itself in natural wind. We measured the static pressures on the ground with accurate pressure transducers of the absolute pressure type and investigated the characteristics of the static pressure on the ground. The relationship between the static pressure on the ground and the internal pressure of these prism models on the ground was also investigated. We found that static pressures on the ground fluctuated to an extent comparable with the wind pressures on the prism model and that lower frequency components of the static pressures on the ground were strongly correlated with the velocity pressures of the large-scale winds high above the ground, which could be accounted for by Bernoullis theorem.