Geoscience Reference
In-Depth Information
(a)
(b)
(c)
(d)
−80
−40
0
40
80
Fig. 2.21 Profiles of waves formed by running (thin line) and piston-like (thick line) displacements
at time moment
t
= 50 for
L
= 10; (a-d) correspond to
v
= 0
.
2
,
0
.
5
,
1 and 10;
τ
= 50, 20, 10 and 1
Fig. 2.22 Energy of
waves excited by piston-
like displacement versus
displacement duration for
various linear dimensions of
the active region. Curves 1-4
correspond to
L
= 10, 5, 2
and 1
The quantity
W
equals twice the potential energy of the wave. The calculation
of energy was performed for the time moment
t
= 50(
H
/
g
)
1
/
2
, when energy redis-
tribution between the potential and kinetic energies had been totally completed and
the value of
W
no longer depended on time.
The results of calculations are presented in Fig. 2.22 as dependences of the en-
ergy of a wave excited by a piston-like displacement of the basin bottom,
W
1
,
upon the displacement duration
τ
. The energy values are normalized to the quan-
2
0
/
2, representing the specific potential energy of a rectangular
elevation of height
tity
W
0
=
ρ
gb
η
η
0
and length
b
of the free surface of a liquid. As the duration of
a piston-like displacement increases the wave energy undergoes a monotonous de-
crease. Moreover, the energy depends essentially on the size of the generation area.
Curves 1-4 in Fig. 2.22 correspond to values of parameter
b
/
H
= 10, 5, 2 and 1.
Note that these results, naturally, do not contradict the data presented in Fig. 2.14.