RIB Laboratory Experiments
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Double Delta Design in the Fourth Series
Four series of laboratory experiments have been conducted to verify, evaluate, and enhance the RIB design. The first and third series were conducted at the U.S. Army Engineer Waterways Experiment Station (WES) in Vicksburg, MS. The second and fourth series were conducted at the O.H. Hinsdale Wave Research Laboratory at Oregon State University (OSU) in Corvallis, OR.
First Series
In the first phase, an initial RIB design using rigid PVC pipe was tested to validate the concept. In the second phase of this first series, additional tests were performed to evaluate the effect of the RIB curtain and different leg diameters. The results from both phases indicated that sea state 3 could be reduced to sea state 2 (a reduction on the order of 50 percent).
Second Series
O.H. Hinsdale Wave Research Laboratory, Oregon State University
Based on the success of the first series, a second series of laboratory experiments was conducted at OSU in August, 1995, at a scale of 1 to 36. These experiments use directional spectral wave conditions and were designed to evaluate additional enhancements and modifications. The tests were performed with single and tandem barrier arrangements in the simulated 75-ft water depth. Incident conditions corresponded to the upper end of sea state 5, with a wave period of 6 sec and a wave height of 8 ft. For the single RIB, wave attenuation or reduction of 65 percent was achieved, enough to reduce this wave to sea state 2. For the tandem RIB, the transmitted wave was reduced even further, to 23 percent of its incident value, corresponding to a reduction to the low end of sea state 2.
Third Series
RIB design next to scaled cargo vessel
A third series of experiments was conducted in the L-Shape flume at WES in January and February, 1996. The purpose of these tests was to evaluate four potential designs of the RIB cross section for an initial field study of a 1-to-4 scale prototype, scheduled for May-June 1996. The inverted triangle or "delta-shaped" design was identified as the most promising.
Fourth Series
Wave Attentuation Plot
Click here to view the laboratory video.
The delta shaped design was extensively studied in the final series, at OSU in March, 1996, at a scale of 1 to 32 with sea state 3 to 5 (survival) multidirectional waves. The purpose of these tests was to finalize the design for the 1-to-4 scale field tests and to evaluate anchor loads. The figure shown above is a three-dimensional plot of the wave attenuation in the lee of the RIB for the case of 5 s period and a wave height of 5 ft. With these results, we felt confident to go to the field with a 1-to-4 field test at Duck, NC.