TWO-DIMENSIONAL SEICHE IN A BASIN SUBJECTED TO INCIDENT WAVES

B. Le Mehaute

Abstract


Seiche movements in lakes have for a long time been submitted to the calculations of the most competent scientists.

Studies of seiche in open basins subject to the action of ocean waves are not so numerous and above all they are less rigorous. However the studies of Lord RAYLEIGH, HONDA, TERADA, YOSHIOA, ISITANI and HANSEN can be mentioned, and the important work by PROUDMAN on tide movements.(which often have a similar character to seiches), the studies of NEUMANN introducing the notion of hydraulic impedance, and those of LAMOEN on the theory of estuaries etc.

More recently MC MOWN made theoretical and experimental studies at the Laboratoire Dauphinois d'Hydrauligue, for circular and square harbours.

Formulae have been known for a long time giving the resonance period of long basins: basins which are sufficiently long for the oscillations to be considered only in the direction of the basin's length. By analogy with sound tubes two cases have been considered: that of basins completely closed and that of basins completely open.

Standing wave; open basin; incident waves

After a short review of the usefulness of maritime structures, particularly vertical wall breakwaters, long term observations of hydrogeological breaking on the bottom of Italy's Seas, as caused by the subaqueous source of fresh water, are discussed. The correlation between hydrogeological breaking and wave motion perturbation produced by compressed air or by oil is presented. These considerations are related to the observations of Admiral Alessandro Cialdi on the morphological breaking of waves above sand banks, thus producing calmness in the upper water.

Therefore, it appears possible to establish a very suggestive analogy between the atomic disintegration of the transformation of potential energy of the oscillatory tide wave into kinematic energy of its components (because of breaking), in accordance with the disintegration of the circular motion.

Keywords


seiche; breakwaters; hydrogeological breaking

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