Modelling Wave-Structure-Foundation Interaction for Marine Gravity Structures (WaSFI)

• Applicant: Dr.-Ing. Hisham Elsafti
• Subject Area: Geotechnics, Hydraulic Engineering
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 310375313

This project primarily aims at developing a partitioned strongly coupled CFD-CSD model system in OpenFOAM, named wasfiFoam, for the simulation of wave-structure-foundation interaction (WaSFI) with a particular focus on stepwise failure of marine gravity structures. The similarity between the Navier-Stokes and the fully dynamic, coupled Biot equations will be utilized for solving the fluid mass and momentum balance equations simultaneously inside and outside deformable porous media with an Eulerian fluid mesh. A Lagrangian background mesh will be used to solve the momentum balance equation of the skeleton-fluid mixture with modelling of soil plasticity under cyclic loading and frictional contact for soil-structure interaction. The immersed boundary method (IBM) will be used to update the fluid domain depending on the structure motions. The solution of the soil constitutive relation will be implemented in GPUs to reduce the computational time. A multiphase fluid treatment with inter-phase momentum transfer and a Volume-Of-Fluid (VOF) approach for describing the air-water interface will be considered. Moreover, wafsiFoam will be coupled with a far-field wave model to provide more realistic wave conditions (e.g. tsunamis and storm surges). wasfiFoam and its constituents will be validated against benchmark cases as well as available large-scale model tests from the Large Wave Flume (GWK). The validated model system will be applied for an extensive parameter study aiming at (i) enhancing the insight in the processes underlying the stepwise failure mechanism of marine gravity structures (e.g. effect of structure rocking motion on uplift pressure, effects of air bubble kinematics on breaking wave impact and pore fluid compressibility/soil consolidation, etc.), (ii) consolidating and refining the Load eccentricity concept developed in the PhD study of the Principal Applicant, together with a more precise definition of the four LEC regimes proposed for marine gravity structures under different wave conditions, and (iii) refining and extending the simplified nonlinear mass-spring-dashpot model (also developed in the aforementioned PhD study) to include more complex structure configurations. wasfiFoam, together with further tools and results generated in the project, will be well-documented and published under the GNU General Public License (GPL).

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Hocine Oumeraci