Coastal Engineering 42 Z2001. 199218
www.elsevier.comrlocatercoastaleng
Establishing uniform longshore currents in a large-scale sediment
transport facility
David G. Hamilton a,), Bruce A. Ebersole b
a
C5-310 Cain Ridge Road, Vicksburg, MS 39180, USA
b
US Army Engineer Research and Deelopment Center, Coastal and Hydraulics Laboratory, 3909 Halls Ferry Road,
Vicksburg, MS 39180-6199, USA
Received 30 November 1999; received in revised form 3 May 2000; accepted 27 September 2000
Abstract
A large-scale laboratory facility for conducting research on surf-zone sediment transport processes has been constructed
at the U.S. Army Engineer Research and Development Center. Successful execution of sediment transport experiments,
which attempt to replicate some of the important coastal processes found on long straight beaches, requires a method for
establishing the proper longshore current. An active pumping and recirculation system comprised of 20 independent pumps
and pipelines is used to control the cross-shore distribution of the mean longshore current. Pumping rates are adjusted in an
iterative manner to converge toward the proper settings, based on measurements along the beach. Two recirculation criteria
proposed by Visser wCoastal Eng. 15 Z1991. 563x were also used, and they provided additional evidence that the proper total
longshore flow rate in the surf zone was obtained. The success of the external recirculation system and its operational
procedure, and the degree of longshore uniformity achieved along the beach, are the subjects of this paper. To evaluate the
performance of the recirculation system, and as a precursor to sediment transport experiments, two comprehensive test series
were conducted on a concrete beach with straight and parallel contours Z1:30 slope., one using regular waves and the other
using irregular waves. In the regular wave case, the wave period was 2.5 s and the average wave height at breaking was
approximately 0.25 m. In the irregular wave case, the peak wave period was 2.5 s and the significant breaking wave height
was approximately 0.21 m. The longshore current recirculation system proved to be very effective in establishing uniform
mean longshore currents along the beach in both cases. This facility and the data presented here are unique for the following
reasons: Z1. the high cross-shore resolution of the recirculation system and the ease with which changes can be made to the
longshore current distribution, Z2. the degree of longshore uniformity achieved as a percentage of the length of the basin
Zeven near the downdrift boundary., Z3. the scale of the wave conditions generated, and Z4. the relatively gentle beach slope
used in the experiments Zcompared to previous laboratory studies of the longshore current.. Measured data are provided in an
appendix for use in theoretical studies and numerical model development and validation. q 2001 Elsevier Science B.V. All
rights reserved.
Keywords: Longshore currents; Surf zone currents; Wave and current measurements; Laboratory experiments; Large-scale laboratory
facility
)
Corresponding author. Tel.: q -601-634-1597; fax: q -601-634-4314.
1
1
E-mail address: cherylquillin@juno.com
ZD.G. Hamilton..
0378-3839r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 8 - 3 8 3 9 Z 0 0 . 0 0 0 5 9 - 4
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