Introduction 1.3 Basics 3
Introduction
aim to provide skills for determining stability and hydrodynamics of ships and submarines; for evaluating
strength and integrity of marine materials and structures; for protecting ocean systems against corrosion
and biofouling; for characterizing generation, propagation, and reception of underwater sound; for processing
and analyzing ocean data; for developing algorithms for
control and automation of marine vehicles; and for designing, developing, testing, and demonstrating ocean
systems.
An understanding of the physics of oceanographic
processes enables modeling and prediction of at-sea
conditions and their variability. It develops an awareness of various phenomena in the water column, including such processes as the thermocline, and wind-driven
and geostrophic currents. Winds, waves, and currents
with random characteristics lead to dynamic sea states
that range from states corresponding to routine operational conditions to those associated with extreme
events. The forces associated with such meteorological
and oceanic (metocean) conditions are correspondingly
dynamic, random, and range from routine to extreme.
They have to be accounted for in designing robust ocean
and coastal structures and in planning and conducting
offshore operations. Oceanographic and metocean processes are described in Chaps. 2–4.
Subsurface pressure, temperature, and salinity are
physical properties of some importance in the deep
ocean environment. Pressure ordinarily increases linearly with water depth, but is also a function of temperature and salinity. Submarines and housings for
electronics of deep-water systems have to be designed
so that they can withstand such pressures and require
specially designed gaskets to prevent high-pressure water leaking into compartments of the systems. It is
believed that Woods Hole Oceanographic Institution’s
unmanned deep-sea research submarine Nereus was
lost in 2014 off New Zealand at a depth of nearly 10 km,
where the pressure exceeds 1000 times the atmospheric
pressure, due to an implosion of one of its components.
While the temperature in the ocean below a mixed layer
drops rapidly in a thermocline, it typically does not drop
below approximately 2
ı C. Properties of seawater are
described in detail in Chap. 5.
Damage due to marine corrosion that arises through
contact with seawater or through exposure to the atmosphere in coastal areas continues to be a major problem;
this includes corrosion in engines operating at sea or exposed to salt-laden air. It typically accounts for 30% of
failures on ships and other marine equipment. A World
Corrosion Organization report [1.3] estimates that the
annual cost of damage due to marine corrosion worldwide is over $1.8 trillion. Corrosion destroys materials
through chemical reaction with its environment and the
rate at which it impacts structures depends on the type
of metal or metal alloys, and the design of the structures as well as the environmental conditions; presence
of microbial organisms; and processes such as cavitation that can damage material surfaces [1.4]. Corrosion
is typically controlled through use of coatings, cathodic
protection, use of inhibitors, chemical dosing of the
local environment, or use of less corrosive materials, including composites, in structures. Properties of marine
corrosion are discussed in Chap. 6.
Maximizing the operational efficiency of ships and
submarines continues to be an important goal in marine transportation. In hydromechanics, fundamentals
of drag, lift, and propulsion as well as such features as
turbulence, boundary layers, jets, shear layers and wake
resistance, and vortex-induced vibrations and galloping
carry over from aerodynamics with the difference that
the density of seawater is over 800 times greater than
that of air. However, phenomena such as cavitation and
bubble generation, and wave-induced forces on vehicles
and offshore structures require special consideration in
hydromechanics. In addition, for vehicles operating on
or near the free surface, an additional contribution to
vehicle drag or resistance arises that is associated with
waves generated by the vehicle. Correspondingly, for
vehicles operating on or near the free surface, in addition to Reynolds number, a dimensionless parameter,
the Froude number, Fr D U=
p
gl, where U and l are,
respectively, the characteristic speed and length, and
g is the acceleration due to gravity, governs the flow
characteristics. The wave-making resistance of ships
is typically characterized by the Froude number. Hydromechanics is discussed in Chap. 7.
Acoustics, electromagnetics, and optics are important sensing mechanisms in underwater operations and
have led to significant efforts in development of associated sensor and sensor platform technologies and
operations. Underwater sound is generated through vibrational activities as a pressure pulse in the water that
propagates at speeds in the range of 14001600 m=s at
frequencies typically in the band 1 Hz–1 MHz with corresponding wavelengths in the range of 1:5 km–1:5 mm.
The sound undergoes transmission losses through absorption and scattering through refraction, reflection,
and destructive interference of sound waves. The speed
of sound decreases with decrease in temperature and
increases with depth. This gives rise to existence of
a minimum at mid-depth and the variability in sound
speed with depth leads to bending or refraction of sound
waves toward region of lower speed. A sound wave
generated in the thermocline bends downward at first
toward region of lower speed and then upward as the
speed increases with depth. This leads to a particularly interesting phenomenon called the SOFAR (sound
Introduction
aim to provide skills for determining stability and hydrodynamics of ships and submarines; for evaluating
strength and integrity of marine materials and structures; for protecting ocean systems against corrosion
and biofouling; for characterizing generation, propagation, and reception of underwater sound; for processing
and analyzing ocean data; for developing algorithms for
control and automation of marine vehicles; and for designing, developing, testing, and demonstrating ocean
systems.
An understanding of the physics of oceanographic
processes enables modeling and prediction of at-sea
conditions and their variability. It develops an awareness of various phenomena in the water column, including such processes as the thermocline, and wind-driven
and geostrophic currents. Winds, waves, and currents
with random characteristics lead to dynamic sea states
that range from states corresponding to routine operational conditions to those associated with extreme
events. The forces associated with such meteorological
and oceanic (metocean) conditions are correspondingly
dynamic, random, and range from routine to extreme.
They have to be accounted for in designing robust ocean
and coastal structures and in planning and conducting
offshore operations. Oceanographic and metocean processes are described in Chaps. 2–4.
Subsurface pressure, temperature, and salinity are
physical properties of some importance in the deep
ocean environment. Pressure ordinarily increases linearly with water depth, but is also a function of temperature and salinity. Submarines and housings for
electronics of deep-water systems have to be designed
so that they can withstand such pressures and require
specially designed gaskets to prevent high-pressure water leaking into compartments of the systems. It is
believed that Woods Hole Oceanographic Institution’s
unmanned deep-sea research submarine Nereus was
lost in 2014 off New Zealand at a depth of nearly 10 km,
where the pressure exceeds 1000 times the atmospheric
pressure, due to an implosion of one of its components.
While the temperature in the ocean below a mixed layer
drops rapidly in a thermocline, it typically does not drop
below approximately 2
ı C. Properties of seawater are
described in detail in Chap. 5.
Damage due to marine corrosion that arises through
contact with seawater or through exposure to the atmosphere in coastal areas continues to be a major problem;
this includes corrosion in engines operating at sea or exposed to salt-laden air. It typically accounts for 30% of
failures on ships and other marine equipment. A World
Corrosion Organization report [1.3] estimates that the
annual cost of damage due to marine corrosion worldwide is over $1.8 trillion. Corrosion destroys materials
through chemical reaction with its environment and the
rate at which it impacts structures depends on the type
of metal or metal alloys, and the design of the structures as well as the environmental conditions; presence
of microbial organisms; and processes such as cavitation that can damage material surfaces [1.4]. Corrosion
is typically controlled through use of coatings, cathodic
protection, use of inhibitors, chemical dosing of the
local environment, or use of less corrosive materials, including composites, in structures. Properties of marine
corrosion are discussed in Chap. 6.
Maximizing the operational efficiency of ships and
submarines continues to be an important goal in marine transportation. In hydromechanics, fundamentals
of drag, lift, and propulsion as well as such features as
turbulence, boundary layers, jets, shear layers and wake
resistance, and vortex-induced vibrations and galloping
carry over from aerodynamics with the difference that
the density of seawater is over 800 times greater than
that of air. However, phenomena such as cavitation and
bubble generation, and wave-induced forces on vehicles
and offshore structures require special consideration in
hydromechanics. In addition, for vehicles operating on
or near the free surface, an additional contribution to
vehicle drag or resistance arises that is associated with
waves generated by the vehicle. Correspondingly, for
vehicles operating on or near the free surface, in addition to Reynolds number, a dimensionless parameter,
the Froude number, Fr D U=
p
gl, where U and l are,
respectively, the characteristic speed and length, and
g is the acceleration due to gravity, governs the flow
characteristics. The wave-making resistance of ships
is typically characterized by the Froude number. Hydromechanics is discussed in Chap. 7.
Acoustics, electromagnetics, and optics are important sensing mechanisms in underwater operations and
have led to significant efforts in development of associated sensor and sensor platform technologies and
operations. Underwater sound is generated through vibrational activities as a pressure pulse in the water that
propagates at speeds in the range of 14001600 m=s at
frequencies typically in the band 1 Hz–1 MHz with corresponding wavelengths in the range of 1:5 km–1:5 mm.
The sound undergoes transmission losses through absorption and scattering through refraction, reflection,
and destructive interference of sound waves. The speed
of sound decreases with decrease in temperature and
increases with depth. This gives rise to existence of
a minimum at mid-depth and the variability in sound
speed with depth leads to bending or refraction of sound
waves toward region of lower speed. A sound wave
generated in the thermocline bends downward at first
toward region of lower speed and then upward as the
speed increases with depth. This leads to a particularly interesting phenomenon called the SOFAR (sound