Seiche (redirected from Underwater wave)

seiche: see wave, in oceanography.

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seiche [sāsh]

(fluid mechanics)

An oscillation of a fluid body in response to the disturbing force having the same frequency as the natural frequency of the fluid system.

(oceanography)

A standing-wave oscillation of an enclosed or semienclosed water body, continuing pendulum-fashion after cessation of the originating force, which is usually considered to be strong winds or barometric pressure changes.

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Seiche 

a standing wave of long period (from several minutes to tens of hours) that arises in large or small enclosed basins of water, such as seas, lakes, and bays. Seiches result from the interference of waves created by external forces, for example, sharp changes in atmospheric pressure, wind, or seismic phenomena, with waves reflected from the end of the basin. Seiches involve oscillation of the entire mass of water, so that there always exist one or more lines (points a and a’ in Figure 1, a and b), called nodes or nodal lines, along which the level does not change.

Figure 1

Seiches may be mononodal (Figure l, a), binodal (Figure l, b), and so forth, with amplitudes from a few millimeters to several meters. For example, seiches in Lake Geneva have attained an amplitude of 2 m with a period of more than I hr. In the Bay of Algiers seiches have attained amplitudes as high as 1 m and periods somewhat longer than 1 min, and in the Sea of Azov seiches with periods up to 23 hr and amplitudes of 10–25 cm have been reported.