- 作者: 趙繼昌
- 作者服務機構: 國立成功大學航空及太空工程研究所
- 中文摘要: 據佛蘭克爾(J. Frenkel)與皮奧特(M.A. Biot)的研究結論顯示,一充滿液體之多孔性介質(porous solid)在動態狀況下,含存在有三種動力波:快速壓力波(dilatational wave), ,低速壓力波, ,及剪力波(shear wave),S,分別以三個不同之傳遞速度 , 及 傳遞前進。顧名思意,其中快速壓力波之傳遞速度 ,自較其他兩者為大。 本報告對平面諧振波射至一無應力表面時,所發生之反射現象,作一詳盡之探討。一般來說,相對應於每一種入射波,都存在有很多不同的反射波。當入射波為低速壓力波, ,或剪力波,S,時,根據其傳遞速度 及 之相對值,可得知有一個或二個臨界角的存在。若入射角小於臨界角,那麼反射波就不再包括各種不同的波;取而代之的是一些在表面上的運動。若存在有一個波,其入射角比兩個臨界角都來得小,就會產生全反射現象。在臨界反射情況下出現的波,其振幅會隨著與無應力表面之距離成線性增加。 若 < ,至少有一個Rayleigh表面波永遠存在著,反之,若 > 就不一定如此。在此情況下我們便演繹出一個為其存在性的條件。
- 英文摘要: According to previous investigations made by J. Frenkel and M.A. Biot, there exist three body wavesin a fluid-filled porous solid. They are a fast dilatational wave, , of velocity ; a slow dilatational wave, , of velocity ; and a shear wave, S, of velocity . The velocity is larger than either or . In this report the reflection phenomenon of plane harmonic waves at the traction-free surface of ahalf-space is examined. It is found that for each type of incident wave there are, in general, reflected wavesof all types. For incident or S wave there exist either one or two critical angles, depending on the rela-tive values of and , such that for incidence angles smaller than a critical angle, the reflected waves donot include all types of waves but some surface motions instead. For a wave incident at an angle smallerthan both critical angles, if existent, total reflection occurs. In the cases of critical reflection there appearwaves whose amplitudes increase linearly with the distance from the free surface. If > there exists always one possible Rayleigh-type surface wave in a half-space. On the otherhand, if < Rayleigh-type surface waves are not always possible; in this case a criterion is established todetermine whether or not this type of wave could exist.
- 中文關鍵字: wave propagation; reflection; fluid-filled porous medium
- 英文關鍵字: --