The calculation results for Case 3 are displayed in Figures 22, 23, and 24,
where cf = 0.009 was found with the roller model included, and cf = 0.007
without the roller model. Again, the shift in the peak of the longshore current
is well captured, and overall the agreement improves by including the roller
model. However, the width of the measured current distribution is somewhat
underestimated, which might be remedied with an improved formulation for
the lateral mixing. The present formulation for the mixing is related to the
local wave height and bottom orbital velocity. This typically yields a
satisfactory description of the mixing outside the surf zone, but inside the surf
zone the mixing could be underestimated because both the wave height and
bottom orbital velocity decrease. In reality, the mixing should increase
because of the breaking and associated strong turbulence. Some alternative
formulations of the lateral mixing are discussed in the following paragraphs.
Figure 23 displays the calculated and measured mean water elevation,
and it is clearly seen that including the roller model yields significantly
improved results, although the setup seems to be overestimated close to shore
in very shallow water. The wave height is also well predicted as shown in
Figure 24.
The results for Case 4 (see Figures 25, 26, and 27) exhibit the same basic
characteristics as the calculations for Cases 1 and 3. The peak in the
longshore current distribution agrees well with the measurements if the roller
model is employed, but the width of the current distribution is somewhat