Accession Number : ADA182741

Title :   A Numerical Model for Shoaling and Refraction of Second-Order Cnoidal Waves Over an Irregular Bottom.

Descriptive Note : Final rept. Jan 85-Apr 86,

Corporate Author : COASTAL ENGINEERING RESEARCH CENTER VICKSBURG MS

Personal Author(s) : Hardy,Thomas A ; Kraus,Nicholas C

PDF Url : ADA182741

Report Date : May 1986

Pagination or Media Count : 200

Abstract : A numerical model for calculating shoaling and refraction of finite-amplitude waves in shallow water is presented. The model is designed to employ second-order cnoidal wave theory, can be used also. A brief review of water-wave theory is given, followed by an outline of a second-order cnoidal wave theory derivation. A description is provided of the basic similarities and differences between cnoidal wave theory and the more commonly used small-amplitude wave theory. Methods for efficient calculation of cnoidal wave theory are derived. The model calculates water wave height and direction directly at numerical grid points, resulting in a greater ease in calculation over models using the ray tracing method. A derivation is given of an expression for the energy flux of second-order cnoidal waves which is used in calculating wave height. The irrotationality wave number equation, adapted for cnoidal wave theory, was used to calculate wave angle. Model results for shoaling and reflection over a plane bottom showed that second-order cnoidal waves shoaled more than small-amplitudes waves but less than first-order cnoidal waves and refracted less than small-amplitude waves but more than first-order cnoidal waves. Second-order cnoidal waves were found to match experimental shoaling data more accurately than either small-amplitude or first-order cnoidal waves.

Descriptors :   *NUMERICAL ANALYSIS, *MATHEMATICAL MODELS, *WATER WAVES, COMPUTATIONS, EFFICIENCY, MODELS, GRIDS(COORDINATES), BOTTOM, REFRACTION, HEIGHT, WAVES, RAY TRACING, ANGLES, SHALLOW WATER, FREQUENCY, WAVE EQUATIONS, THEORY

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE