Question 14.3: Waves of period 8 s in deep water approach the shore from th......
Waves of period 8 s in deep water approach the shore from the south-west, as shown in Fig. 14.27. In the figure, bed contours are shown as broken lines. Draw the wave refraction pattern.
Referring to Fig. 14.27, the steps for drawing the refraction diagram are as follows.
1. Sketch the wave crest at deep water and divide the crest into equal strips AB, BC, CD, etc. Usually ABCD. . . are drawn at deep water, which may be taken to be d \simeq 0.5\, L_0 . \text { From Fig. } 14.4, L_0=100 \, m for T = 8 s.
2. Compute celerities at A, B, C, D. . . as c_{ A }, c_{ B }, c_{ C }, c_{ D } . . . using Fig. 14.3.
3. Choose a convenient time of travel t, which is 10 s in this example. Obviously t should be small for closely packed bed contours in order to achieve better accuracy. Draw the orthogonals or rays at A, B, C, D. . . and advance these rays by c_{ A } t, c_{ B } t, c_{ C } t, c_{ D } t ,. . . to A’, B’, C’, D’. . . .
4. Repeat steps 2 and 3 at A’, B’, C’, D’ . . . to advance the rays for time t.
5. The lines drawn normal to the rays are the wave crests. Rays and crests are sketched until wave breaking is reached. Refraction coefficients may be determined from the spacing of the rays and wave heights calculated if required.
The refraction pattern for the example is shown in Fig. 14.27.
