Sloshing impacts captured in 110 full-scale tests


Report unveils the innovative techniques MARIN has developed for measuring full and large-scale sloshing impacts within the Sloshel project.


S


loshel aims to validate existing and new novel methods for the assess- ment of containment systems sub-


jected to sloshing in membrane LNG tanks. The project was organised together with Gaztransport & Technigaz (GTT), Bureau Veritas and Shell. Successively Ecole Cent- rale Marseille, American Bureau of Shipping, Chevron, Lloyd’s Register, Det Norske Veritas and ClassNK joined the project.


The Sloshel experiment was designed to collect data on sloshing impacts and the associated structural response of real LNG containment systems, such as NO96 and Mark III. In the experiment the sloshing impact is generated in a flume by breaking waves on a vertical wall with an embedded containment system. So far, 110 full-scale tests have been carried out. This data set is now being analysed to capture sloshing physics, to define scale and hydro-elastic effects and to validate the assessment methods.


Mirek Kaminski & Edwin van de Bunt m.kaminski@marin.nl


16 report


To measure or not to measure? Before designing the measuring system and sen- sors a crucial question had to be answered, “What has to be measured in order to make the validation possible?” Answering the question led to a decision to measure the following: spatial and temporal evolution of


the impact, pressures on the impacted surface and strains in the impacted contain- ment system.


The first quantity was especially challeng- ing because the Delta flume of Deltares, which was selected for the tests, has con- crete walls and non-transparent water that makes video observation very difficult.


Emergence of iCAM For this reason MARIN, in cooperation with Optel in the Netherlands, developed the Impact Captur- ing Matrix Sensor (iCAM). This novel iCAM sensor consists of 640 single optical sensors distributed over an area of 3 metres high and 1.5 metres wide. The distance between sensors is 7.5cm and 10cm in the vertical and horizontal direction, respectively. Each sensor is able to distinguish air, aerated water and solid water independently of whether its surface is dry or covered by a water film. During testing the iCAM sensor was placed on the flume wall just in front of the test panel. The iCAM’s disturbing effect on breaking waves was minimised by its small 25mm thickness. Sampling with 3 or 15 kHz, the iCAM sensor delivered crucial data for the project, facilitating impact clas- sification and determining the governing parameters such as the volumes of en- trapped air pockets.


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