VELOCITY (M/SEC)
22
in
Figure 2.1: Longshore current profiles for different friction formulations for an 11 second,
1.028 meter wave at 17.28 degrees to a 1:25 plane beach.
most often used since it requires less computation time and more importantly the Gaussian
integration involving the reed part of the gradient of complex amplitudes at times produces
stability problems.
The lateral mixing term in Eqs. (2.1) and (2.2) also involve several simplifying assump
tions. The first assumption is found in the derivation of the two depth integrated equations
of motion where it is assumed that the turbulent shear stress term -pu'v1 is independent
of depth. The other assumption is that the process of momentum transfer due to turbulent
fluctuations can be represented by a product of a mixing length parameter and derivatives
of the mean current. This is what is done in the present study and also in previous studies.
Ebersole and Dalrymple (1979), Vemulakonda (1984), and Yan (1987) all used the formu
lation given by Longuet-Higgins (1970b) in which he developed an analytical expression for
the cross shore distribution of the longshore current velocities using a linearized friction
formulation as described above, linear waves at an angle to the normal of a plane beach,