67
mm
Figure 5.2: Comparison of numerical results from the model with experimental results of
Hansen and Svendsen (1979). Wave set-up and wave heights for a 2 second wave on a beach
slope of 1:34 and incident wave height of 7 centimeters.
and in the slope of the set-up. Although the problem of where the set-up begins is still
present, the curvature of the mean water surface is the same for both cases. It is also quite
clear that the diminution of the wave height is not constant as is assumed by the spilling
breaker assumption.
In figure 5.2 the breaking wave height in the experiment is much greater than in the
model. This is because linear wave theory cannot adequately predict wave shoaling. Ven-
gayil and Kirby (1986) were able to duplicate the shoaling recorded in the experiments of
Hansen and Svendsen (1979) by numerically solving coupled equations for the many har
monic components. Their results showed that in the shoaling process prior to wave breaking,
wave energy was transmitted to the higher frequency components. Their work however is
not adaptable for use in the current model since it is not known how to dissipate energy