Accession Number:

ADA609434

Title:

Model for the Computation of Time-Steady Nearshore Currents

Descriptive Note:

Technical note

Corporate Author:

ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS COASTAL AND HYDRAULICS LAB

Personal Author(s):

Report Date:

2003-12-01

Pagination or Media Count:

15.0

Abstract:

The Coastal and Hydraulics Engineering Technical Note CHETN herein introduces a new model for the computation of depth-dependent time-steady currents in the surf zone. Under the assumptions of longshore uniformity, monochromatic and unidirectional waves, one-dimensional 1-D models have predicted the steady depth-integrated longshore current with reasonable accuracy in the regions of intense breaking e.g., Bowen 1969 Longuet-Higgins 1970 Kraus and Larsen 1991. The addition of random wave fields with directional spread Battjes 1974 Thornton and Guza 1986 produce similar results but indicate a difference in the magnitude of the horizontal mixing terms. It is, however, necessary to also predict the vertical structure of time-steady currents in the surf zone to reliably compute sediment transport rates. Indeed, concentrations of sediment are found to be orders of magnitude larger in the near-bed boundary layer where fluid velocities are, in general, smaller than the depth-averaged value. It is, therefore, of practical importance to predict the vertical variation of nearshore currents. The phase resolving equations of fluid motion may be best suited for a physically based prediction of sediment transport. Lin and Liu 1998, for instance, solved the Reynolds equations with an algebraic nonlinear Reynolds stress model. Karambas and Koutitas 2002 and Kobayashi and Johnson 2001 used Boussinesq and nonlinear shallow-water formulations, respectively. These time-dependent numerical models, however, are not suitable to most practical engineering problems due to the prohibitively large computation time.

Subject Categories:

  • Physical and Dynamic Oceanography
  • Numerical Mathematics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE