Effect of Fluid Acceleration on Bedload Sediment Transport
in the Surf Zone
Calantoni, J., and Drake, T.G., 1998, Effect
of fluid acceleration on bedload sediment transport in the surf
zone: EOS Trans. AGU, 79 (45), Fall Meeting Suppl., F416 (Special
Session: Nearshore Processes)
Breaking waves commonly
generate near-bed fluid acceleration exceeding 1/4 the gravitational
acceleration. Discrete-particle computer simulations of bedload
sediment transport over a plane bed indicate a strong linear dependence
of the transport rate on the third moment of the acceleration,
in addition to a dependence on the third moment of velocity. Only
the velocity dependence appears in the prevailing sediment transport
models of Bailard and Bowen; such models were shown previously
to underpredict considerably net transport rates for a variety
of waveforms typical of the nearshore. A new empirical relationship
for transport rates derived from simulation data predicts bedload
transport rates in the surf zone using quantities commonly measured
in the field. Predicted rates also depend on such derived parameters
as wave skewness and asymmetry. Simulations were conducted for
nine different waveforms having maximum near-bed fluid velocities
ranging from 0.5 m/s to 1.5 m/s and maximum fluid accelerations
ranging from 0.7 m/s/s to 4.1 m/s/s using particles having the
material properties of quartz and a distribution of sizes with
a mean of 1.1 mm. Predicted transport rates compare favorably
with available experimental data.
Supported by
the Coastal Dynamics Program of the Office of Naval Research.