Elementary Loading Processes (ELP) involved in breaking wave impacts: findings from the Sloshel project
Author W. Lafeber, L. Brosset, H. Bogaert
Title Elementary Loading Processes (ELP) involved in breaking wave impacts: findings from the Sloshel project
Conference/Journal ISOPE 22th International Offshore and Polar Engineering Conference, Rhodes, Greece
Year 2012

Abstract
MarkIII is one of the containment systems designed by GTT for LNG storage or transportation. It features a corrugated stainless steel membrane which modifies locally the flow of LNG in the tanks of LNG carriers, hence modifies the loads during sloshing impacts.

The interactions between breaking waves and the MarkIII corrugated membrane were described in Bogaert, Brosset and Kaminski (2010). The observations were based on the large scale impact tests of the Sloshel project performed in 2009. In this paper, these interactions are described again but based this time on the Sloshel full scale impact tests performed in 2010. In both test campaigns, unidirectional breaking waves were generated in flume tanks in order to break onto instrumented walls. Full scale tests were performed with a water height at rest of 4 m and the wall was covered by the real MarkIII membrane. Large scale tests were performed at scale 1:6, including the corrugated surface covering the wall, mimicking accurately the MarkIII membrane. In both cases pressure sensors were positioned in between the corrugations. Special sensors were designed to measure the forces on corrugations. The wave-corrugation interactions were captured by high speed cameras synchronized with the data acquisition system.

Qualitatively, the interactions observed at full scale are very similar to those observed at scale 1:6. However, full scale measurements allow a more in depth analysis of the local phenomena involved. The paper shows that the different kinds of interactions between breaking waves and either a flat or a corrugated wall induce loads that are combinations of only a few Elementary Loading Processes (ELPs): 1. direct impact, 2. building jet along the wall from the impact area and 3. compression/expansion of entrapped or escaping gas. In case of a corrugated wall, additional combinations of ELPs occur because new local flow situations intervene. However, these are still combinations of the same ELPs. Therefore, the ELPs are considered as the building blocks of any load on a wall impacted by a wave.

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