1.5. OVERVIEW OF HYDRAULIC PHYSICAL MODELS
9
c. Sometimes all forcing functions and boundary conditions acting in nature are not included in the physical model, and
the missing functions and conditions need to be assessed
and accounted for in evaluation of model results. For example, wind shear stresses acting on the free surface may
generate significant nearshore circulation currents in nature that would be absent in any model which included
only mechanical wave generation.
d. Except in rare instances, physical models are undeniably
more expensive to operate than numerical models; and in
situations where the numerical model gives reliable results
with engineering accuracy, the numerical model is the tool
of choice.
Despite the shortcomings inherent in experimental physical modeling, a
capability to model accurately the processes in the nearshore zone is essential to a wide range of problems (Dean 1985), and understanding physical
model laboratory and scale effects will allow researchers to utilize these
models to address problems that cannot wait until a complete, or at least
sufficient, mathematical description of the process is available. Even in
the face of laboratory and scale effects, it is possible to test model sensitivity by varying input conditions, and thus better interpret model results
(Kamphuis 1991).
In the future we can look forward to better understanding of scale effects, improved similarity criteria, better instrumentation, automation of
model operation, and new and innovative avenues of research (Martins
1989).
1.5
Overview of Hydraulic Physical Models
1.5.1 What is a Physical Model?
The term “physical model” conjures up different images for different people, depending on their own personal experience. Consequently, providing
a precise, all-encompassing, definition of physical modeling becomes difficult. To some, the term “physical model” might be limited to small-scale
reproduction of actual prototype situations, such as harbors or breakwaters. To others, the term may exclude laboratory experimentation looking
at microscale processes, such as turbulence. A fairly broad definition of
physical modeling is given below.
A Physical Model is a physical system reproduced (usually at a reduced size) so that the major dominant forces
9
c. Sometimes all forcing functions and boundary conditions acting in nature are not included in the physical model, and
the missing functions and conditions need to be assessed
and accounted for in evaluation of model results. For example, wind shear stresses acting on the free surface may
generate significant nearshore circulation currents in nature that would be absent in any model which included
only mechanical wave generation.
d. Except in rare instances, physical models are undeniably
more expensive to operate than numerical models; and in
situations where the numerical model gives reliable results
with engineering accuracy, the numerical model is the tool
of choice.
Despite the shortcomings inherent in experimental physical modeling, a
capability to model accurately the processes in the nearshore zone is essential to a wide range of problems (Dean 1985), and understanding physical
model laboratory and scale effects will allow researchers to utilize these
models to address problems that cannot wait until a complete, or at least
sufficient, mathematical description of the process is available. Even in
the face of laboratory and scale effects, it is possible to test model sensitivity by varying input conditions, and thus better interpret model results
(Kamphuis 1991).
In the future we can look forward to better understanding of scale effects, improved similarity criteria, better instrumentation, automation of
model operation, and new and innovative avenues of research (Martins
1989).
1.5
Overview of Hydraulic Physical Models
1.5.1 What is a Physical Model?
The term “physical model” conjures up different images for different people, depending on their own personal experience. Consequently, providing
a precise, all-encompassing, definition of physical modeling becomes difficult. To some, the term “physical model” might be limited to small-scale
reproduction of actual prototype situations, such as harbors or breakwaters. To others, the term may exclude laboratory experimentation looking
at microscale processes, such as turbulence. A fairly broad definition of
physical modeling is given below.
A Physical Model is a physical system reproduced (usually at a reduced size) so that the major dominant forces