8
CHAPTER 1. INTRODUCTION
6. Physical contact with the fluid element remains the best
guide for intuitive discovery. The physical model demonstrates visually, and with credibility, what will happen. It
stimulates the imagination and guides creative engineering solutions at a level that cannot be reached by theory
or computer printouts.
Le Méhauté (1990) concluded by postulating that decreased interest in
physical modeling of coastal processes, brought about by the emergence of
numerical models, will be reversed due to the needs of the next generation
of numerical models. Knowledge gaps in present mathematical representations of flow processes will dictate the direction of future experimental
efforts because further progress in numerical models can only be gained by
better understanding of the basic laws of fluid flow. Scale models still are
the best tool that an engineer can have to discover and verify engineering
solutions.
1.4 Disadvantages of Physical Models
Although there are several distinct advantages in favor of laboratory experimentation and physical modeling, we must temper our enthusiasm somewhat with the realization that physical hydraulic models have some serious
drawbacks, most notably:
a. Scale effects occur in models that are smaller than the
prototype if it is not possible to simulate all relevant variables in correct relationship to each other. Scale effects are
to the experimenter what simplifying assumptions are to
the theorist (Le Méhauté 1990). A common scale effect in
coastal models is viscous forces that are relatively larger
in the scale model than in the prototype.
b. Laboratory effects can influence the process being simulated to the extent that suitable approximation of the prototype is not possible. Typical laboratory effects arise from
the inability to create realistic forcing conditions and from
the impact model boundaries have on the process being
simulated. A common laboratory effect arises when unidirectional waves are generated in the model to approximate
directional waves that occur in nature. The experimenter
must determine whether this is a reasonable approximation.
CHAPTER 1. INTRODUCTION
6. Physical contact with the fluid element remains the best
guide for intuitive discovery. The physical model demonstrates visually, and with credibility, what will happen. It
stimulates the imagination and guides creative engineering solutions at a level that cannot be reached by theory
or computer printouts.
Le Méhauté (1990) concluded by postulating that decreased interest in
physical modeling of coastal processes, brought about by the emergence of
numerical models, will be reversed due to the needs of the next generation
of numerical models. Knowledge gaps in present mathematical representations of flow processes will dictate the direction of future experimental
efforts because further progress in numerical models can only be gained by
better understanding of the basic laws of fluid flow. Scale models still are
the best tool that an engineer can have to discover and verify engineering
solutions.
1.4 Disadvantages of Physical Models
Although there are several distinct advantages in favor of laboratory experimentation and physical modeling, we must temper our enthusiasm somewhat with the realization that physical hydraulic models have some serious
drawbacks, most notably:
a. Scale effects occur in models that are smaller than the
prototype if it is not possible to simulate all relevant variables in correct relationship to each other. Scale effects are
to the experimenter what simplifying assumptions are to
the theorist (Le Méhauté 1990). A common scale effect in
coastal models is viscous forces that are relatively larger
in the scale model than in the prototype.
b. Laboratory effects can influence the process being simulated to the extent that suitable approximation of the prototype is not possible. Typical laboratory effects arise from
the inability to create realistic forcing conditions and from
the impact model boundaries have on the process being
simulated. A common laboratory effect arises when unidirectional waves are generated in the model to approximate
directional waves that occur in nature. The experimenter
must determine whether this is a reasonable approximation.