著者

桃井 高夫

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.43, no.4, pp.745-754, 1966-03

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In a series of works already completed, the theories on a long wave in an L-shaped canal have been developed under the first, second and third approximations. In the present work, these theories are utilized to calculate the wave heights and phases for a canal of uniform width and for discussing the behaviors of the waves in the canal in question. Then the following facts are ascertained: - When kd(k: a wave number of the incident waves, d: a width of the canal) increases, the wave height of the reflected waves is linearly augmented from zero to amount to about 20 percent of that of the incident waves at kd=1.0. Then the advancing waves diminish monotonically in height to reach about 95 percent of the incident waves(if these values are evaluated in energy, the reflected waves for the range kd < 1.0 are at most 5 percent of the incident waves and the advancing waves are propagated nearly without loss of energy). As far as the phases are concerned, when kd is small, the reflected waves have a phase difference of π/2 from the incident waves. As kd increases, such a difference decreases linearly until the value reaches zero at kd■l.5. In other words, the incident and reflected waves make up quasi-standing waves, instead of complete standing waves, under the condition λ■4d (λ: a wavelength of the incident waves).今までおこなわれてきた一連の研究で,筆者はL字水防における長波の理論を第1,第2,第3近似までの範囲で展開を試みた.本報告では,これらの理論を用い,水路の幅が不変なモデルについて数値解析をおこない,L字水路における長波の状態を調べた.そしてつぎのようなことを知つた.(1)波高の変化については,kd(k:進入波の波数,d:水防の幅)が0のとき,反射波は全くなく,kdが増加するにつれてその波高はほとんど線型的に増加する,しかしその量は非常に小さくkd=1.0の近くで,進入波の波高の20パーセント程度である(エネルギーに換算すると5パーセントにすぎない).