EM 1110-2-1100 (Part II)
30 Apr 02
Diffraction for a breakwater gap of one wavelength width where φ = 15 deg
(f) Bowers and Welsby (1982) conducted a physical model study of wave diffraction through a gap
between two breakwaters whose axes are angled (rather than being collinear, i.e. 180 deg). Breakwater
interior angles of 90 deg and 120 deg were employed. As would be expected, angling the breakwaters
increased the heights behind the breakwater compared with the results for collinear breakwaters. But the
increases were relatively small - up to 15 percent for 120-deg interior angles and up to 20 percent for 90-deg
interior angles, when gap widths were in excess of half a wavelength.
(g) Memos (1976, 1980a, 1980b, 1980c) developed an approximate analytical solution for diffraction
through a gap formed at the intersection of two breakwaters having axes that are not collinear but intersect
at an angle. The point of intersection of the breakwater axes coincides with the tip of one of the breakwaters.
Memos' solution can be developed for various angles of wave approach.
d. Irregular wave diffraction.
(1) The preceding discussion of wave diffraction was concerned with monochromatic waves. The effects
of wave diffraction on an individual wave depend on the incident wave frequency and direction. Thus, each
component of a directional wave spectrum will be affected differently by wave diffraction and have a
different KN value at a particular point in the lee of a breakwater.