Accession Number : ADA020028

Title :   Effects of a Breakwater on Nearshore Currents Due to Breaking Waves.

Descriptive Note : Technical memo.,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CIVIL ENGINEERING

Personal Author(s) : Liu,Philip L-F. ; Mei,Chiang C.

Report Date : NOV 1975

Pagination or Media Count : 264

Abstract : This study provides a semiempirical theory of nearshore currents due to breaking waves in the presence of a shore-connected breakwater or an offshore breakwater. The effects of diffraction are studied in addition to refraction by shoaling waters. The concept of radiation stresses applied to uniform longshore current and rip currents forms the starting point of the theory. Many empirical relations included in this study with regard to the surf zone are similar to, and extrapolations of, the ones used in related works. Ignoring convective inertia and lateral turbulent diffusion, the governing equations are solved numerically by the method of finite differences. Sample results for stream functions and mean sea levels are plotted for various beach profiles or incidence angles. For the offshore breakwater, the predicted current pattern is consistent with available laboratory observations and the known tendency of tombolo formation; for the shore-connected breakwater. the computed flow pattern exhibits cells in both downwave and upwave regions. Directly relevant observations have not been found but part of the predicted features has some indirect experimental support. More experimental and theoretical work is suggested.

Descriptors :   *Breakwaters, *Ocean waves, *Littoral drift, Beach erosion, Ocean currents, Surf, Offshore, Diffraction, Sandbars, Theses, Computer programs

Subject Categories : Civil Engineering
      Marine Engineering

Distribution Statement : APPROVED FOR PUBLIC RELEASE