dissipation of mean turbulent kinetic energy (TKE) calculated in a one-
equation TKE transport model in which the production term for the TKE is
taken from the wave energy balance equation. Nairn, Roelvink, and
Southgate (1990) and Deigaard, Justesen, and Fredsoe (1991) also applied a
one-equation TKE transport model with the governing hydrodynamic
equations to obtain an improved description of the mean water-surface
elevation and undertow.
Smith, Larson, and Kraus (1993) numerically modeled the longshore
current by adding a transport equation for the TKE to the wave energy
balance equation and the cross-shore and longshore momentum equations.
The momentum transport associated with the turbulence was estimated from
the computed distribution of the TKE through parameterization, which
required assumptions concerning the ratios between the turbulent fluctuations
in the different coordinate directions (i.e., degree of isotropy). By including
the turbulent transport in the alongshore momentum equation, a shift in the
driving force was obtained that produced the desired shoreward translation of
the peak in the current distribution. However, because measurements of the
turbulence in breaking waves are rare (probably due to operational
difficulties in the surf zone with suspended sediment), some empirical
coefficients had to be introduced in connection with the parameterization.
The values on these coefficients were essentially determined through