We initially evaluated the ability of BOUSS-2D to simulate the propagation

of waves through a gap into a rectangular harbor basin. The basin is 1,200 m

wide, 600 m long, and 10 m deep. The width of the opening at the harbor

entrance is 120 m.

The first case considered is a regular wave with period *T *= 7 s propagating in

a direction normal to the breakwaters. The corresponding ratio of the gap width,

grid spacings ∆x = ∆y = 3 m and time-step size ∆t = 0.15 s. A 60-m-wide damp-

ing layer was placed around the perimeter of the basin to absorb outgoing waves.

Figure 8 shows a snapshot of the instantaneous water-surface elevation produced

by the BOUSS-2D model.

The normalized wave height distribution predicted by BOUSS-2D is com-

pared with the numerical solution of Isaacson and Qu (1990) in Figure 9.

Isaacson and Qu (1990) used a boundary integral technique to solve the 2-D

Helmholtz equation, which is a reduced form of the mild-slope equation for

water of constant depth. Good agreement is generally observed between the wave

height predictions from the numerical models. Small oscillations can be seen in

the Boussinesq model predictions, especially for the smaller wave height con-

tours. This is due to partial wave reflection from the radiation boundaries. Reflec-

tion coefficients of the order of 5 to 10 percent at the boundaries have been

observed to cause such oscillations in wave height contour lines (Isaacson and

Qu 1990)

We next investigated the propagation of irregular multidirectional waves

through the gap. The sea state is characterized by a JONSWAP wave spectrum

with peak period *T*p = 7 s and peak enhancement factor γ = 3.3. A wrapped-

normal distribution with a standard deviation of 20 deg was used for the direc-

tional distribution of wave energy. The double-summation method was used to

synthesize time-histories of velocity fluxes along the incident wave boundary for

the BOUSS-2D simulations.

Figure 10 shows a snapshot of the instantaneous water-surface elevation

produced by the BOUSS-2D model. The normalized wave height distribution

predicted by BOUSS-2D is compared with the numerical solution of Isaacson

and Qu (1990) in Figure 11. Good agreement is observed. As expected, the

41

Chapter 5 Model Validation

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