which are difficult to describe in form or motion, and which may be comnrised of several components are termed complex waves. Sinusoïdal or
simple harmonie waves are examples of simple waves since their surface
profile can be described by a single sine or cosine function. A wave is
periodic if its motion and surface profile recur in equal intervals of .
time. A wave form which moves relative to a fluid is called a progressive
wave-, the direction in which it moves is termed the direction of wave
propagation. If a wave form merely moves up and down at a fixed.position,
it is called a complété standing wave or a clapotis. A progressive wave
is said to be a wave of permanent form if it is propagated without experiencing any changes in free surface configuration.
Water waves are considered oscillatory or nearly oscillatory if the
water particle motion is described by orbits, which are closed or nearlyclosed for each wave period. Linear, or Airy, theory describes pure
oscillatory waves. Most finite amplitude wave théories describe nearly
oscillatory waves since the fluid is moved a small amount in the direction
of wave advance by each successive wave. This motion is termed mass
transport of the waves. When water particles advance with the wave, and
do not return to their original position, the wave is called a wave of
translation. A solitary wave is an example of a wave of translation.
It is important to distinguish between varions types of water waves
that may be generated and propagated. One way to classify waves is by
wave period T (the time for a wave to travel a distance of one wave
length), or by the reciprocal of T, the wave frequency f. One illustration of classification by period or frequency is given by Kinsman (1965)
and shown in Figure 2-1. The figure shows the relative amount of energy
contained in océan waves having a particular frequency. Of primary concern
are those waves referred to as gravity waves in Figure 2-1, having periods
from 1 to 30 seconds. A narrower range of wave periods, from 5 to 15
seconds, is usually more important in Coastal engineering problems. Waves
in this range are referred to as gravity waves since gravity is the
principal restoring force; that is, the force due to gravity attempts to
bring the fluid back to its equilibrium position. Figure 2-1 also shows
that a large amount of the total wave energy is associated with waves
classified as gravity waves; hence gravity waves are extremely important
in dealing with the design of Coastal and offshore structures.
Gravity waves can be further separated into two States:
(a) seas, when the waves are under the influence of wind in a
générâting area, and
(b) swell, when the waves move out of the generating area and
are no longer subjected to significant wind action.
arLUSUally made Up of steePer waves with shorter periods and
'W
w rv SUIlace aPPears much more confused than for swell.
caused it wh i
3
WaVe’ i’e*’ free from the disturbing force that
on which thp
C01lslst t0 some extent of forced waves, i.e., waves
on which the disturbmg force is applied continuously.
Swell
2-4
simple harmonie waves are examples of simple waves since their surface
profile can be described by a single sine or cosine function. A wave is
periodic if its motion and surface profile recur in equal intervals of .
time. A wave form which moves relative to a fluid is called a progressive
wave-, the direction in which it moves is termed the direction of wave
propagation. If a wave form merely moves up and down at a fixed.position,
it is called a complété standing wave or a clapotis. A progressive wave
is said to be a wave of permanent form if it is propagated without experiencing any changes in free surface configuration.
Water waves are considered oscillatory or nearly oscillatory if the
water particle motion is described by orbits, which are closed or nearlyclosed for each wave period. Linear, or Airy, theory describes pure
oscillatory waves. Most finite amplitude wave théories describe nearly
oscillatory waves since the fluid is moved a small amount in the direction
of wave advance by each successive wave. This motion is termed mass
transport of the waves. When water particles advance with the wave, and
do not return to their original position, the wave is called a wave of
translation. A solitary wave is an example of a wave of translation.
It is important to distinguish between varions types of water waves
that may be generated and propagated. One way to classify waves is by
wave period T (the time for a wave to travel a distance of one wave
length), or by the reciprocal of T, the wave frequency f. One illustration of classification by period or frequency is given by Kinsman (1965)
and shown in Figure 2-1. The figure shows the relative amount of energy
contained in océan waves having a particular frequency. Of primary concern
are those waves referred to as gravity waves in Figure 2-1, having periods
from 1 to 30 seconds. A narrower range of wave periods, from 5 to 15
seconds, is usually more important in Coastal engineering problems. Waves
in this range are referred to as gravity waves since gravity is the
principal restoring force; that is, the force due to gravity attempts to
bring the fluid back to its equilibrium position. Figure 2-1 also shows
that a large amount of the total wave energy is associated with waves
classified as gravity waves; hence gravity waves are extremely important
in dealing with the design of Coastal and offshore structures.
Gravity waves can be further separated into two States:
(a) seas, when the waves are under the influence of wind in a
générâting area, and
(b) swell, when the waves move out of the generating area and
are no longer subjected to significant wind action.
arLUSUally made Up of steePer waves with shorter periods and
'W
w rv SUIlace aPPears much more confused than for swell.
caused it wh i
3
WaVe’ i’e*’ free from the disturbing force that
on which thp
C01lslst t0 some extent of forced waves, i.e., waves
on which the disturbmg force is applied continuously.
Swell
2-4