The rapid growth of marine aquaculture around the world accentuates issues of sustainability and environmental impacts of large-scale farming systems. One potential mitigation strategy is to relocate to more energetic offshore locations. However, research regarding the forces which waves and currents impose on aquaculture structures in such conditions is still scarce. The present study aimed at extending the knowledge related to live blue mussels (Mytilus edulis), cultivated on dropper lines, by unique, large-scale laboratory experiments in the Large Wave Flume of the Coastal Research Center in Hannover, Germany. Nine-months-old live dropper lines and a surrogate of 2.0 m length each are exposed to regular waves with wave heights between 0.2 and 1.0 m and periods between 1.5 and 8.0 s. Force time histories are recorded to investigate the inertia and drag characteristics of live mussel and surrogate dropper lines. The surrogate dropper line was developed from 3D scans of blue mussel dropper lines, using the surface descriptor Abbott–Firestone Curve as quality parameter. Pull-off tests of individual mussels are conducted that reveal maximum attachment strength ranges of 0.48 to 10.55 N for mussels that had medium 3.04 cm length, 1.60 cm height and 1.25 cm width. Mean drag coefficients of C_D = 3.9 were found for live blue mussel lines and C_D = 3.4 for the surrogate model, for conditions of Keulegan–Carpenter number (KC) 10 to 380, using regular wave tests.

Offshore wind energy can contribute significantly to achieve greenhouse gas neutrality in the near future. But the planning, construction and operation of offshore wind parks is associated with high costs. In particular, the operation and maintenance (OandM) costs account for a major fraction and in turn are also dependent on appropriate weather windows in which working vessels can operate. A precise knowledge of how wind, sea state and currents affect each other, as well as the most accurate possible prediction of the development, is essential to maximize these periods and reduce the resulting costs. For the German Bight, the high-resolution coastal wave model (CWAM) is often used for this purpose. The CWAM is based on WAM (Hasselmann et al. 1988) and was developed by the German Meteorological Service (DWD) and German Maritime and Hydrographic Agency (BSH) in cooperation with the Helmholtz-Zentrum Hereon. Compared to other WAM models it offers the advantages of higher resolution, as well as the consideration of current speeds and tide-dependent water depths. The BSH also operates multiple measuring stations in the German Bight, which enable real-time investigation of sea state parameters. The general objective of this study is to compare historical data sets from in situ measurements in the German Bight with numerical forecast data and to identify which factors influence the accuracy of the CWAM and why deviations occur.