Tunami Wave in Osaka Bay (II)

[摘要] (2) Propagation of Tunami Wave in Osaka Bay.The condition of propagation of Tunami in the Osaka bay may be percepted by the model experiments accomplished by Mr. Matuo. The model used for this experiment is 16 meters in length and 8 meters in width. A long wave was sent from the place corresponding to the Tomogasima Suido (Straits) by means of a wooden plate moving forward from its initial position inclined backwards with its end hinged on the bottom. The wave motion thus made is recorded at various places at the surface, and both the travel time curve and the heights of the first wave are shown in Figs. 2 and 3 by broken curves. Besides, in Fig. 1 is shown the feature of the propagation of head of the Ist wave.We assume the wave to be a part of the harmonic one having a period of 4, 7 sec. and the “narrow sea theory” be applicable appoximately, to the phenomenon then the equation of this motion can be expressed where ζ is the surface elevation, and b(x), S(x) are breadth and sectional area of the bay respectively. Admitting these assumptions, we treat the case of the solution ζ=fcos (vt-φ) and substituting it in (I) and making the coefficients of sine and cosine to zero, we have From (2) we get where k denotes the constant which should be determined by initial conditions. Substituting (3) in (I) we haveBy integrating (4) mechanically under the initial conditions which are the same as observed in the experiment, we can evaluate the values off f for several places and applying them to (3) we may have the wave velocity for their places, consequently we can determine the travel time curve mechanically. These values thus obtained are shown in the table (I) and indicated graphically in Figs. 2 and 3, in which the values obtained experimentally are also traced. Fig. 2 shows the close coincidence of the calculated travel time curve with that observed. But as is seen in Fig. 3 the calculated amplitude f does not fit so closely with that observed. This fact is considered to be due to the feature of the progression of the wave.

[学科分类] 大气科学