Accession Number : ADA195540

Title :   Nonlinear Mechanisms for the Generation of Nearshore Wave Phenomena.

Descriptive Note : Final rept. 1 Jul 85-29 Feb 88,

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

Personal Author(s) : Akylas, T R

PDF Url : ADA195540

Report Date : Apr 1988

Pagination or Media Count : 5

Abstract : Theoretical study of various generation mechanisms of nonlinear edge wave phenomena on beaches through asymptotic and numerical techniques. In particular, the nonlinear longshore modulational instability of edge wave packets has been investigated. Also, the forced response of water waves near cut off conditions in a shallow channel was studied. Finally, numerical techniques for computing fully nonlinear periodic edge wave phenomena on shallow beaches have been developed. The studies have shown that (i) large-scale longshore variations of standing subharmonic edge waves are unstable and eventually give rise to recurrence phenomena. (ii) asymptotic analysis of the forced response of water waves near cut-off conditions leads to a forced Kadomtsev-Petviashvili equation. Numerical solutions of this equation indicate that steady state is reached only if dispersion is negative; otherwise, periodic generation of localized wave groups is found. (iii) there is numerical evidence that there is a critical steepness above which nonlinear periodic edge waves cease to exist; this threshold value of the steepness depends on the beach slope. Keywords: Nearshore wave phenomena; Shallow beaches; Water waves; Beach slope. (JHD)

Descriptors :   *NONLINEAR DIFFERENTIAL EQUATIONS

Subject Categories : Physical and Dynamic Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE