Accession Number : ADA190668

Title :   An Analytical Model of Wave-Induced Longshore Current Based on Power Law Wave Height Decay.

Descriptive Note : Final rept. Jul 85-Oct 86,

Corporate Author : COASTAL ENGINEERING RESEARCH CENTER VICKSBURG MS

Personal Author(s) : Smith, Jane M ; Kraus, Nicholas C

PDF Url : ADA190668

Report Date : Jan 1988

Pagination or Media Count : 134

Abstract : An analytical model of the wave-induced longshore current is derived. A unique feature of the model is an empirical power law expression, developed in this study, employed to describe the broken wave height in the surf zone. The model also includes the effect of wave setup, finite incident wave angle, and lateral mixing. The power law expression represents the surf zone wave height decay significantly better than the linear decay profile assumed in previous longshore current models. The exponent in the power law expression is determined to be a function of the beach slope and the wave height to water depth ratio at wave breaking. The longshore current model is derived by balancing the longshore stresses: local wave stress, lateral mixing stress, and bottom friction stress. The solution for the longshore current distribution is an infinite power series which is truncated to second order. The model gives the longshore current as a function of distance offshore, breaking wave conditions (height, depth, and angle), beach slope, friction coefficient, and a parameter, P, that expresses the relative importance of lateral mixing and bottom friction. Estimates of the longshore current distribution using this model agree with previous results in the appropriate limits, but the estimated current varies significantly under certain breaking wave conditions and beach slopes. Wave setup is also derived using the power law expression of the broken wave height. For the limit amount of setup data examined, the setup based on the power law wave height decay represents the data better than the calculated setup based on linear wave height decay.

Descriptors :   *SURF, *OCEAN CURRENTS, ANGLES, OCEAN BOTTOM, COEFFICIENTS, DECAY, DEPTH, SPATIAL DISTRIBUTION, ESTIMATES, FRICTION, HEIGHT, INFINITE SERIES, MATHEMATICAL MODELS, MODELS, OFFSHORE, POWER, POWER SERIES, RANGE(DISTANCE), RATIOS, SHORES, STRESSES, TRUNCATION, WATER WAVES, OCEAN WAVES, ANGLE OF INCIDENCE, MIXING, HORIZONTAL ORIENTATION, EXPONENTIAL FUNCTIONS, BEACHES, SLOPE, STRESS ANALYSIS

Subject Categories : Physical and Dynamic Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE