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There are no limits in terms of scale effects. Numerical models, once developed, can be
adapted easily to many different prototype situations. There is no problem in the storage or
duplication of the model. Today computer facilities are far more available than laboratory
facilities. Computer models easily allow for sensitivity testing of the importance of an
individual variable and any specific feature of the model can be monitored.
Numerical models also have their disadvantages. In fact some of their advantages
are also their disadvantages. For example, being able to monitor any feature also means
that the computer will deliver only the information that is explicitly specified. Thus an
investigation of one aspect will not indicate problems with other aspects. Though any
mechanism for which the governing equation is known can be modeled, the model is only as
good as the assumptions involved in the equations. For example, the forces exerted on the
water column by the complex interaction between the fluid motion and the bottom are not
totally understood and are often greatly simplified. Another example is the use of depth
integrated two-dimensional models of fluid flows when the reality is three-dimensional. Both
of the above are incorporated in the present study. Knowing the correct equation does not
always make for successful computer modelling since the complexity of the equations may
make for difficulties (for example solving for the complete three-dimensional flow field using
the Navier-Stokes equations). Computer time and cost for large programs can often be
significant.
1.1 Literature
This section is a brief history and literature review of the attempts of the coastal
engineering profession to obtain predictions of waves and currents in the nearshore region
given the offshore wave conditions.
The extension of Snells law which governs optical wave refraction to the analogous
problem of water waves over straight and parallel contours has been known for some time.
Johnson, OBrien, and Isaacs (1948) reported graphical methods for constructing wave
refraction diagrams. Two methods were reported, one producing wave fronts and the second