CHAPTER 1. INTRODUCTION
12
that will yield valuable insight into the details of very complex hydrodynamic processes. These models allow systematic investigation of both
steady-state or transient flow phenomena, and they are the key for advancing numerical modeling capabilities.
1.5.3 Types of Physical Models in Coastal Engineering
In terms of their physical characteristics, physical models used to study
nearshore coastal processes can be divided into two classes: fixed-bed models and movable-bed models.
Fixed-bed models have solid boundaries that cannot be modified by
the hydrodynamic processes ongoing in the model. (However, the boundaries can modify the hydrodynamics!) Fixed-bed models are used to study
waves, currents, or similar hydrodynamic phenomena in the laboratory under controlled circumstances. They are also used to study the interaction
of hydrodynamic forces with solid bodies, such as pilings, breakwaters, harbor basins, etc. The scaling effects associated with fixed-bed models are
reasonably well understood and much confidence can be given to the results
of carefully-conducted fixed-bed model studies.
Examples of fixed-bed model studies in two-dimensional facilities include wave tank tests to examine wave propagation and transformation,
studies of wind wave generation in flumes, breakwater stability tests, studies on wave/current interaction, measurement of hydrodynamic forces on
structures, and examination of fluid kinematics.
Three-dimensional fixed-bed models are more involved, and they examine such coastal engineering problems as wave penetration into harbors,
harbor seiching response to short waves, transformation of directionallyspread irregular waves, interaction of oblique waves and currents, stability
of complex coastal structures, and other challenging engineering problems.
Movable-bed models, as the name implies, have a bed composed of
material that can react to the applied hydrodynamic forces (hopefully in
a similar manner as the prototype response). The scaling effects inherent
in movable-bed physical models used for studying sedimentary problems
are not as well understood as they are for fixed-bed models. Consequently,
movable-bed model results must be carefully reviewed in the context of
previous, similar models that have demonstrated success in reproducing
prototype bed evolution.
Examples of two-dimensional movable-bed coastal models include studies of beach profile evolution, dune erosion, ripple development, scour at the
toes of coastal structures, response of beach fills to storms, response of cobble beaches to wave action, and bedform translation under unidirectional
currents.
12
that will yield valuable insight into the details of very complex hydrodynamic processes. These models allow systematic investigation of both
steady-state or transient flow phenomena, and they are the key for advancing numerical modeling capabilities.
1.5.3 Types of Physical Models in Coastal Engineering
In terms of their physical characteristics, physical models used to study
nearshore coastal processes can be divided into two classes: fixed-bed models and movable-bed models.
Fixed-bed models have solid boundaries that cannot be modified by
the hydrodynamic processes ongoing in the model. (However, the boundaries can modify the hydrodynamics!) Fixed-bed models are used to study
waves, currents, or similar hydrodynamic phenomena in the laboratory under controlled circumstances. They are also used to study the interaction
of hydrodynamic forces with solid bodies, such as pilings, breakwaters, harbor basins, etc. The scaling effects associated with fixed-bed models are
reasonably well understood and much confidence can be given to the results
of carefully-conducted fixed-bed model studies.
Examples of fixed-bed model studies in two-dimensional facilities include wave tank tests to examine wave propagation and transformation,
studies of wind wave generation in flumes, breakwater stability tests, studies on wave/current interaction, measurement of hydrodynamic forces on
structures, and examination of fluid kinematics.
Three-dimensional fixed-bed models are more involved, and they examine such coastal engineering problems as wave penetration into harbors,
harbor seiching response to short waves, transformation of directionallyspread irregular waves, interaction of oblique waves and currents, stability
of complex coastal structures, and other challenging engineering problems.
Movable-bed models, as the name implies, have a bed composed of
material that can react to the applied hydrodynamic forces (hopefully in
a similar manner as the prototype response). The scaling effects inherent
in movable-bed physical models used for studying sedimentary problems
are not as well understood as they are for fixed-bed models. Consequently,
movable-bed model results must be carefully reviewed in the context of
previous, similar models that have demonstrated success in reproducing
prototype bed evolution.
Examples of two-dimensional movable-bed coastal models include studies of beach profile evolution, dune erosion, ripple development, scour at the
toes of coastal structures, response of beach fills to storms, response of cobble beaches to wave action, and bedform translation under unidirectional
currents.