UN ESPERIMENTO IN MARE SULLA RIFLESSIONE DELLE ONDE

A small breakwater (wall 12x2.1 m, water depth at the wall basis 1.5 m), consisting of a steel truss with metal reflecting panels, was built at sea in front of ​​Reggio Calabria. Thirty transducers were functioning along the wall and in front of it till a distance of 7.5 m. Since the first measuraments the confirmation was got of the deep differences between the reflection of the sea waves and the classic reflection of regular waves, as predicted by a recent theory (Boccotti, 1998). In particular, starting on one wave length from the wall, nodes and antinodes tend pratically to disappear, with the apparent big consequences in terms of wave heights. Furthermore, the wave period, not only is not a constant as in the regular waves, but it exhibits even some characteristic jumps at the nodes. A small experimental breakwater wall (wall 12x2.1 m, draft of the vessel at the foot of the wall 1.5 m) in the lattice structure of steel panels with reflective metal, was created in the sea of ​​Reggio Calabria. Along the wall and in front of it, up to a distance of 7.5 m, were sistewmati 30 pressure transducers. Ever since the measures was confirmation of the substantial differences between the reflection of the waves of the sea and the classic reflection of regular waves, as predicted by a recent theory (Boccotti, 1998). In particular, starting from a wavelength from the wall, the nodal points and the points virtually antinodali tend to disappear, with the obvious, large consequences in terms of height of the waves. Furthermore, the period of the waves, not only is not constant as in the classical regular waves, but even has discontinuities in the nodal points. A small experimental breakwater wall (wall 12x2.1 m, draft of the vessel at the foot of the wall 1.5 m) in the lattice structure of steel panels with reflective metal, was created in the sea of ​​Reggio Calabria. Along the wall and in front of it, up to a distance of 7.5 m, were sistewmati 30 pressure transducers. Ever since the measures was confirmation of the substantial differences between the reflection of the waves of the sea and the classic reflection of regular waves, as predicted by a recent theory (Boccotti, 1998). In particular, starting from a wavelength from the wall, the nodal points and the points virtually antinodali tend to disappear, with the obvious, large consequences in terms of height of the waves. Furthermore, the period of the waves, not only is not constant as in the classical regular waves, but even has discontinuities in the nodal points.

Una piccola diga foranea sperimentale a muro (parete di 12x2.1 m, tirante d'acqua al piede della parete 1.5 m)in struttura reticolare di acciaio con pannelli riflettenti metallici, è stata realizzata nel mare di Reggio Calabria. Lungo la parete e davanti ad essa, fino ad una distanza di 7.5 m, sono stati sistewmati 30 trasduttori di pressione. Fino dalle prime misure si è avuta la conferma delle differenze sostanziali tra la riflessione delle onde di mare e la classica riflessione delle onde regolari, come previsto da una recente teoria (boccotti, 1998). In particolare, a partire da una lunghezza d'onda dalla parete, i punti nodali e i punti antinodali tendono praticamente a scomparire, con le evidenti, grandi conseguenze in termini di altezza delle onde. Inoltre il periodo delle onde, non solo non è costante come nelle classiche onde regolari, ma addirittura presenta delle discontinuità nei punti nodali.