Figure 13 shows the LSC distribution for θ = 5, 10, 15, and 20 deg with

Hs = 0.3 m and Tp = 2.5 sec. Three general trends can be seen in this figure.

First, as θ increases, the magnitude of the LSC at the peak of the distribution

significantly increases. The magnitude of the peak LSC equals 0.10, 0.18, 0.23,

and 0.28 m/sec for θ = 5, 10, 15, and 20 deg, respectively. This is a relative

increase of about 80, 28, and 22 percent for each consecutive increase in θ.

Secondly, the cross-shore location of the peak of the LSC distribution remains

constant as θ increases. Thirdly, the width of the LSC distribution remains

reasonably constant as θ increases.

0.40

θ

0.35

5 deg

10 deg

0.30

15 deg

20 deg

0.25

0.20

0.15

0.10

0.05

0.00

0

2

4

6

8

10

12

14

16

18

20

22

Figure 13. Influence of wave direction on required longshore current distribution

Based on these numerical simulations, it was concluded that increasing Hs

strongly influences the magnitude and cross-shore location of the peak of the

LSC distribution, whereas, increasing Tp has a much milder effect. In addition,

increasing θ has a very strong influence on increasing the peak magnitude but no

influence on the cross-shore location of the peak of the LSC distribution.

The first part of this section describes the design wave condition used to

determine the required pumping capacity of the LSC recirculation system.

Subsequent sections apply a factor of safety to the numerical model results, and

incorporate the requirements of conducting experiments with a moveable-bed

beach and a variable operating water level into the design.

21

Chapter 3

Longshore Current Recirculation System

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