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The rapid emergence of the floating offshore wind sector requires the development of new technologies such as dynamic inter-array cables. This work gives an insight into the hydrostatic predesign of such a cable system looking from side view. Numerical analyses are performed to compare two umbilical shapes, namely catenary and lazy wave shape. In a parametric study, water depth and cable length are varied. As outcome, a unique and generalized recommendation for a first umbilical design is presented. Finally, an outlook to the dynamic analysis of umbilicals in future work is given. Keywords Inter-array cable • Floating offshore wind turbine • Hydrostatic analysis Abbreviations AC Alternating current HO Hang-off MAC Max. allowable curvature MBL Minimum breaking load TD Touchdown TSL Target segment length Symbols d Water depth h Height of hang-off l 1∕2∕3 Lazy wave section lengths l max∕min Max./minimum length l total Total cable length x, y, z coordinates

Wave energy converters (WECs) are designed to operate near the resonance region, being excited at or close to its natural frequencies. Therefore, they are strongly affected by the interaction with waves, motion and mooring restraints. Floating WECs, such as point absorbers, present small dimensions in relation to the wave length, being typically subjected to large amplitude motions. An oscillating floating vertical cylinder is a simple representative geometry of WECs and component of many different floating structures. Over the past years it has been addressed in multiple studies revealing several difficulties. The pitch and heave free decay responses of a floating vertical cylinder will be studied throughout this paper. The present case was based on an experiment and subject of different CFD validation studies. Both have found significant discrepancies regarding the damping and natural period of the system, specially for the pitch motion. Throughout this work a rigorous verification study was performed, with special focus on the iterative convergence and discretisation errors relative to the hydrodynamic damping coefficients. Moreover, the main phenomena contributing to the hydrodynamic damping of the system were identified. Furthermore, the results were further compared with an experimental investigation.

With the advancement of high-performance computation capabilities in recent years, high-fidelity modelling tools such as computational fluid dynamics are becoming increasingly popular in the offshore renewable sector. To justify the credibility of the numerical simulations, thorough verification and validation is essential. In this work, preparatory heave decay tests for a freely floating single cylinder are modelled. Subsequently, the surge and sway decays of a linearly moored floating offshore wind turbine model of the OC4 (Offshore Code Comparison Collaboration Continuation) phase II semi-submersible platform are simulated. Two different viscous-flow CFD codes are used: OpenFOAM (open-source), and ReFRESCO (community-based open-usage). Their results are compared against each other and with water tank experiments. For the single-cylinder decay simulations, it is found that the natural period is accurately modelled compared to the experimental results. Regarding the damping, both CFD codes are overly dissipative. Differences and their potential explanations become apparent in the analysis of the flow field data. Meanwhile, large numerical uncertainties especially in later oscillations make a distinct conclusion difficult. For the OC4 semi-submersible decay simulations, a better agreement in damping can be achieved, however discrepancies in results are observed when restricting the degrees of freedom of the platform. Flow field data again reveals differences between the CFD codes. Meanwhile, through the effort to use similar numerical settings and quantify the numerical uncertainties of the CFD simulations, this work represents a stepping stone towards fairer and more accurate comparison between CFD and experimental results.