Physical modelling in coastal engineering: Proceedings of an international conference, Newark, Delaware, August 1981 PDF

INTRODUCTION

Physical models provide the engineer and scientist two significant advantages when studying a particular coastal engineering problem. The first is that nature is used to integrate the appropriate equations which govern the phenomena, whether it be wave propagation into harbors or sand transport on a beach. No simplifying assumptions are used and no unknowns are omitted, as often occurs in analytical or numerical modelling. The second advantage is that the size of the model is much smaller than the prototype, permitting the easier acquisition of relevant data.

There are, of course, drawbacks, such as the introduction of scale effects, which are due to changes in the relative importance of various forces (such as surface tension) as the model becomes smaller than the prototype. Additionally, the model is generally more simplistic than the prototype, for example, the use of monochromatic (single frequency) waves to study real sea states or, since the advent of spectral wave generators, using 'real' sea states, but neglecting wind and other potentially important forces in nature.

The purpose of this introduction is to provide a brief overview of the modelling laws which permit the experimenter to scale the model results up to the prototype size.

In coastal engineering, there are two types of models commonly used, fixed bed models (to study, for example, wave propagation and currents) and movable bed models (to study the deposition and transport of sediment). The modelling criteria for each are different and will be treated separately here.

Author: R.A. Dalrymple