A3 – Hydrodynamics of offshore megastructures and impact processes in and with the marine environment

Over the past four years, Project A3 has provided substantial contributions in understanding the complex interactions between offshore megastructures and the marine environment. As we enter the second funding period from 2025 to 2028, the project aims to build on these findings, moving from fundamental research towards more multi-layered cumulated environmental impacts.

Throughout the initial funding phase, Project A3 addressed fundamental challenges associated with the size increase of offshore structures, particularly in regard to the complex three-dimensional aspects of wave-current-structure interaction.

Central achievements during this period which include novel insights gained predominantly from a structured series of scaled model tests, have been published in a sequence of journal and conference contributions.

The importance of research on the hydrodynamic properties specific to megastructures can be pointed out by the example of Wynants et al. (2024b). The authors extensively examined wave-induced diffraction patterns surrounding large monopiles under influence of a perpendicularly intersecting current. The novel phenomenon of 'current distorted diffraction', specific to large monopiles in directional wave-current-interaction, has been shown to induce new loading scenarios, unrecognized in current design guidelines.

Collaborations with neighbouring subprojects have been included in the design, execution and analysis of joined laboratory experiments, for example leading to forwarded understanding of the complex process of wave-current-structure-seafloor interaction (A03-A04, e.g. Welzel et al 2024).

Further examples of collaborative efforts have led to joined publications on the designated CRC reference site (A1, A3, A5, B2, B3, B4 and Z1, Ribnitzky et al. 2024) or the importance of diffraction patterns in crew transfer manoeuvres (A3-A6, Meyer et al. 2024).

Finally, findings of the individual studies can be contributed to the central digital twin in form of a partial model to refine the chosen mid-fidelity hydrodynamic model towards parametric inclusion of neglected effects (in prep).

Entering the second funding period, Project A3 remains committed to refining the understanding of offshore megastructures subjected to complex environmental forces. In connection to the overall project objective of verification and validation of both digital twin and partial models, the subproject aims to refine the aspects of wave-current-structure interactions towards more lifelike cumulated marine boundary conditions to contribute verified methods based on both laboratory and field data.

In detail, this increased degree of complexity entails three core objectives:

1. Current profiles including wind shear (rather than uniform currents) in interaction with waves
2. The interaction and combined impact of breaking waves on uniform and sheared currents
3. An increased focus on the interconnection to subproject A4, further exploring hydrodynamic seafloor interaction as well as the coupled structure response.

These objectives will be approached through methodical laboratory tests in newly enhanced facilities, such as miniGWK+ and GWK+, alongside comprehensive numerical modelling. Specific focus will be given to wide-ranging collaborative model experiments in the GWK+ in interconnection with a variety of subprojects, building on the expertise developed the large scale model tests of FP1, now including applied SHM as well as realistic pile foundations in a moving bed, designed to generate valuable datasets for validating digital twin simulations. Extensive information on these demonstrator tests can be found in: Link.

Finally, the integration of regional climatic changes and consequent impacts such as storm activity and sea-level fluctuations are crucial areas of investigation. Long-term metocean parameter studies, in collaboration with subproject A5, will support planning for more resilient structure designs capable of adapting to dynamic environmental conditions.