CHAPTER 2
MECHANICS OF WAVE MOTION
2.1 INTRODUCTION
The effects of water waves are of paramount importance in the field
of Coastal engineering. Waves are the major factor in determining the
geometry and composition of beaches, and significantly influence planning
and design of harbors, waterways, shore protection measures, Coastal
structures, and other Coastal Works. Surface waves generally dérivé their
energy from the winds. A significant amount of this wave energy is finally
dissipated in the nearshore région and on the beaches.
Waves provide an important energy source for forming beaches; assorting bottom sédiments on the shoreface; transporting bottom materials onshore, offshore, and alongshore; and for causing many of the forces to
which Coastal structures are subjected. An adéquate understanding of the
fundamental physical processes in surface wave génération and propagation
must précédé any attempt to understand complex water motion in the nearshore areas of large bodies of water. Consequently, an understanding of
the mechanics of wave motion is essential in the planning and design of
Coastal Works.
This chapter présents an introduction to surface wave théories.
Surface and water particle motion, wave energy, and théories used in
describing wave transformation due to interaction with the bottom and
with structures are described. The purpose is to provide an elementary
physical and mathematical understanding of wave motion, and to indicate
limitations of selected théories. A number of wave théories hâve been
omitted. References are cited to provide information on théories not
discussed and to supplément the théories presented.
The reader is cautioned that man’s ability to describe wave phenomena
is limited, especially when the région under considération is the Coastal
zone. Thus, the results obtained from the wave théories presented should
be carefully interpreted for application to actual design of coastal structures or description of the coastal environment.
2.2 WAVE MECHANICS
2.21 GENERAL
Waves in the océan often appear as a confused and constantly changing
sea of crests and troughs on the water surface because of the irregularity
of wave shape and the variability in the direction of propagation. This
is particularly true while the waves are under the influence of the wind.
The direction of wave propagation can be assessed as an average of the
directions of individual waves. A description of the sea surface is
difficult because of the interaction between individual waves. Faster
waves overtake and pass through slower ones from various directions.
Waves sometimes reinforce or cancel each other by this interaction, and
often collide with each other and are transformed into turbulence, and
2-1
MECHANICS OF WAVE MOTION
2.1 INTRODUCTION
The effects of water waves are of paramount importance in the field
of Coastal engineering. Waves are the major factor in determining the
geometry and composition of beaches, and significantly influence planning
and design of harbors, waterways, shore protection measures, Coastal
structures, and other Coastal Works. Surface waves generally dérivé their
energy from the winds. A significant amount of this wave energy is finally
dissipated in the nearshore région and on the beaches.
Waves provide an important energy source for forming beaches; assorting bottom sédiments on the shoreface; transporting bottom materials onshore, offshore, and alongshore; and for causing many of the forces to
which Coastal structures are subjected. An adéquate understanding of the
fundamental physical processes in surface wave génération and propagation
must précédé any attempt to understand complex water motion in the nearshore areas of large bodies of water. Consequently, an understanding of
the mechanics of wave motion is essential in the planning and design of
Coastal Works.
This chapter présents an introduction to surface wave théories.
Surface and water particle motion, wave energy, and théories used in
describing wave transformation due to interaction with the bottom and
with structures are described. The purpose is to provide an elementary
physical and mathematical understanding of wave motion, and to indicate
limitations of selected théories. A number of wave théories hâve been
omitted. References are cited to provide information on théories not
discussed and to supplément the théories presented.
The reader is cautioned that man’s ability to describe wave phenomena
is limited, especially when the région under considération is the Coastal
zone. Thus, the results obtained from the wave théories presented should
be carefully interpreted for application to actual design of coastal structures or description of the coastal environment.
2.2 WAVE MECHANICS
2.21 GENERAL
Waves in the océan often appear as a confused and constantly changing
sea of crests and troughs on the water surface because of the irregularity
of wave shape and the variability in the direction of propagation. This
is particularly true while the waves are under the influence of the wind.
The direction of wave propagation can be assessed as an average of the
directions of individual waves. A description of the sea surface is
difficult because of the interaction between individual waves. Faster
waves overtake and pass through slower ones from various directions.
Waves sometimes reinforce or cancel each other by this interaction, and
often collide with each other and are transformed into turbulence, and
2-1