10
CHA PTER 1. INTROD UCTION
acting on the system are represented in the model in
correct proportion to the actual physical system.
The above definition includes most laboratory experimentation (even
experiments conducted at prototype scale), and thus, may be a somewhat
more encompassing definition than traditionally used.
Many physical models resemble the prototype at a different size, but
they may have different fluids or operate under different conditions. Most
coastal engineering physical models are reduced in size compared to the
prototype; however, there is no reason why the model cannot be larger
than the prototype so that prototype details can be more easily studied.
For example, the motion of red blood cells with a diameter of 8 pm has
been studied in large models (Munson, et al. 1990).
Price (1978) stated that an important property of physical models is the
ability to visualize and observe the process close at hand. He elaborated
by pointing out that instruments have improved modeling, but they cannot
improve the quality of the processes we are trying to scale, and they are
not a substitute for our eyes.
Yalin (1989) reminded us that
A physical model is a precision device used in order to predict
the behavior of a physical phenomenon. A model can be regarded
as reliable only if it is designed correctly. If the design is not
correct, then the model is wrong in principle, and in that case,
the employment of the most sophisticated instrumentation and
measurement-methods can serve only to increase the accuracy
of wrong predictions.
In other words, a model with poor scale determination would be like a ruler
with incorrect markings. The ruler can be used to make measurements, but
the measurements are guaranteed to be wrong!
1.5.2 Goals in Conducting a Physical Model
Svendsen (1985) lists three complementary goals that can be pursued using
a physical model (or laboratory experimentation):
a. Seek qualitative insight into a phenomenon not yet described
or understood (e.g., turbulence formation by wave breaking, formation of scour holes at coastal structures).
b. Obtain measurements to verify or disprove a theoretical result (e.g., nonlinear waves on a uniform current, or interacting nonlinear waves).
CHA PTER 1. INTROD UCTION
acting on the system are represented in the model in
correct proportion to the actual physical system.
The above definition includes most laboratory experimentation (even
experiments conducted at prototype scale), and thus, may be a somewhat
more encompassing definition than traditionally used.
Many physical models resemble the prototype at a different size, but
they may have different fluids or operate under different conditions. Most
coastal engineering physical models are reduced in size compared to the
prototype; however, there is no reason why the model cannot be larger
than the prototype so that prototype details can be more easily studied.
For example, the motion of red blood cells with a diameter of 8 pm has
been studied in large models (Munson, et al. 1990).
Price (1978) stated that an important property of physical models is the
ability to visualize and observe the process close at hand. He elaborated
by pointing out that instruments have improved modeling, but they cannot
improve the quality of the processes we are trying to scale, and they are
not a substitute for our eyes.
Yalin (1989) reminded us that
A physical model is a precision device used in order to predict
the behavior of a physical phenomenon. A model can be regarded
as reliable only if it is designed correctly. If the design is not
correct, then the model is wrong in principle, and in that case,
the employment of the most sophisticated instrumentation and
measurement-methods can serve only to increase the accuracy
of wrong predictions.
In other words, a model with poor scale determination would be like a ruler
with incorrect markings. The ruler can be used to make measurements, but
the measurements are guaranteed to be wrong!
1.5.2 Goals in Conducting a Physical Model
Svendsen (1985) lists three complementary goals that can be pursued using
a physical model (or laboratory experimentation):
a. Seek qualitative insight into a phenomenon not yet described
or understood (e.g., turbulence formation by wave breaking, formation of scour holes at coastal structures).
b. Obtain measurements to verify or disprove a theoretical result (e.g., nonlinear waves on a uniform current, or interacting nonlinear waves).