14.7 Basin oscillations
In a basin the width of which is uniform and much smaller than the length,
oscillations occur in the longitudinal direction. The basins may be ideal-
ized with both ends closed or one end closed. The former is analogous to a
harbour with an entrance at the seaward end, while the latter may be
taken to approximate a bay or an estuary. The oscillations in the harbour
and the estuary will be triggered by the waves or tides at the seaward end.
The fundamental, the first and the second modes of basin oscillations
are shown in Fig. 14.11. The water surface forms antinodes at the vertical
walls and nodes at the open end of the basin. The wavelength in the n-th
node of oscillation Lnis related to length of the basin Lbas follows:
both ends closed, Ln
one end closed and one end open, Ln.
4 Lb
2 n 1
2 Lb
n 1
592 WAVES AND OFFSHORE ENGINEERING
fundamental mode
first mode
second mode
Fig. 14.11 Basin oscillations
