longshore flux was estimated to be relatively small, one larger pump was used in
place of four smaller pumps. The required pump capacities (based on the
numerical simulations) and design pump capacities (as-built) are slightly
different because of the need to minimize cost by selecting pumps with capacities
which were commercially available. In addition, it was prudent to have
additional pumping capacity at the offshore of the system or the result of
uncertainties in estimating the longshore current magnitude in that region.
Required Recirculation Capacity
Design Pumping Capacity
Cross-shore Location (m)
Figure 15. Required and design pumping capacity of the longshore current
The total design capacity of the LSC recirculation system was calculated to
be approximately 1.25 m3/sec. To put this pumping capacity into perspective
with other large-scale laboratory facilities, HR Wallingford (1994) states that the
LSC recirculation system in the Coastal Research Facility has a design capacity
of 1.2 m3/sec (i.e., four axial flow pumps each with a capacity of 0.3 m3/sec).
The LSC recirculation system in the Coastal Research Facility is used to generate
not only wave-driven LSC within the surf zone, but also tidal currents offshore of
the toe of the concrete beach. Therefore, although the purpose of the two
recirculation systems is not exactly the same, the total design pumping capacities
are very similar.
Design of System Components
This section provides a detailed technical description of each of the five sub-
systems that make up each of the 20 independent recirculation systems.
Longshore Current Recirculation System