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Wave-in-deck and vapour pocket model tests

AuthorsJule Scharnke & Rodrigo Ezeta
Conference/JournalMARIN Report 134
Date12 Dec 2022
Reading time12 minutes
Fresh insight into impact load assessment has been gained following two BreaKin JIPs and the IMBOL project, which is
a continuation of the SLING programme.

During the BreaKin JIP (2016-2018) wave-in-deck model tests were carried out in MARIN’s Depressurised Wave Basin (DWB) at two scales (25 and 50), and in atmospheric and depressurised conditions. The objective of the JIP was to get more insight into the scale effects involved in wave-in-deck model tests and to take the first steps towards linking
wave kinematics with measured impact loads. In the ongoing follow-up project, the BreaKin CFD JIP (2020-2023), the model test results are being further analysed and compared to ComFLOW simulations.

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Based on the preliminary results, two major observations have been made:
  • The depressurisation of the testing facility results in a change in gas-to-liquid density ratio and due to this, in a change in air flow between the incoming wave and the deck box. This causes a change of wave shape. For the wave cases tested at scale 25, this resulted in an increase of measured horizontal global impact loads in depressurised conditions compared to atmospheric conditions.
  • The unscaled surface tension results in changes of the free surface instabilities between the tests carried out at scale 25 vs scale 50. As a result, higher global horizontal deck loads are measured at scale 50.
Wave-in-deck impact event in atmospheric condition (left) and depressurised condition (right), measured at scale 25 in MARIN’s Depressurised Wave Basin
High-speed video of a single impact wave in the Atmosphere facility (ATM) from two different angles. Here, the liquid phase is water and the gaseous phase is water vapour. The temperature increases from left to right.