94
3 An Introduction to Surface Waves
B
A
tA
tB
Time
b -
"Eh
.[)
B
t = tB
..Q
Q)
:>
~
A
t = tA
Distance
Fig. 3.9: Wave growth in space and time: a duration-limited wave growth, b fetchlimited growth
Zealand and across the Pacific Ocean to California. It is thought to take the
swell about two weeks to travel this distance (Barber, 1969). Swell waves have
very little effect on the size and progress of locally generated wind waves. They
are able to pass through wind waves without interaction (Massel, 1996a).
3.5.3 Parameters and Functions of Wind-induced Waves
Consider a typical wave record at a given location as shown in Fig. 3.10.
This figure illustrates a set of various waves which occur over a short time.
However, for many applications, it is necessary to identify particular waves
and their associated height and period.
In Fig. 3.2, the wave period, T, was defined as a time interval between two
successive crests. However, in case of random waves it is more practical to define
particular wave periods as the time interval between two successive points at
which the sea surface crosses the mean sea level, when rising upwards. These