Focused wave interactions with floating structures: a blind comparative study

Abstract

The paper presents results from the Collaborative Computational Project in Wave Structure Interaction (CCP-WSI) Blind Test Series 2. Without prior access to the physical data, participants, with numerical methods ranging from low-fidelity linear models to fully non-linear Navier–Stokes (NS) solvers, simulate the interaction between focused wave events and two separate, taut-moored, floating structures: a hemispherical-bottomed cylinder and a cylinder with a moonpool. The ‘blind’ numerical predictions for heave, surge, pitch and mooring load, are compared against physical measurements. Dynamic time warping is used to quantify the predictive capability of participating methods. In general, NS solvers and hybrid methods give more accurate predictions; however, heave amplitude is predicted reasonably well by all methods; and a WEC-Sim implementation, with CFD-informed viscous terms, demonstrates comparable predictive capability to even the stronger NS solvers. Large variations in the solutions are observed (even among similar methods), highlighting a need for standardisation in the numerical modelling of WSI problems.

Investigation of Turbulence Modeling for Point-Absorber-Type Wave Energy Converters

“…Two different WEC structures, W1 and W2, are considered in the following. The structures are based on the systems employed in the blind test series 2 and 3 of the collaborative code project wave structure interaction (CCP-WSI) [55,56] and resemble axisymmetric, cylindrical point-absorber-type devices. The relevant physical properties are shown in Figure 3.…”

Validation of simulated wave energy converter responses to focused waves

“…The experimental tank, WEC-like buoys, and wave parameters are reproduced as specified by the CCP-WSI Blind Test Series 2 project (see CCP-WSI, 2020;Ransley et al, 2020a). The experimental wave tank was the Plymouth University, UK, COAST Laboratory Ocean Basin.…”

“…The results presented in this study were generated after the formal CCP-WSI Blind Test Series 2 comparisons were made. The formal CCP-WSI Blind Test Series 2 results, which were generated without the knowledge of the experimentally measured responses, are reported in van Rij et al (2019b), and Ransley et al (2020a). Fundamentally, the WEC-Sim and STAR-CCM+ models presented in the formal CCP-WSI Blind Test Series 2 comparisons and those presented here are the same, as will be discussed in the following sections.…”

“…As such, the use of a focused wave saves computational and experimental evaluation time while, ideally, still accurately predicting the extreme design loads. In practice, however, the equivalence of focused waves to the stochastic extreme events that they are meant to represent, as well as the ability of computational methods to accurately simulate the prescribed focused waves and the resulting wave structure interactions, are not well validated (Ransley et al, 2017(Ransley et al, , 2019(Ransley et al, , 2020a(Ransley et al, , 2020b).…”

“…This study is carried out in participation with the Collaborative Computational Project in Wave Structure Interaction (CCP-WSI) Blind Test Series 2 (see CCP-WSI, 2020;Ransley et al, 2020a), which is funded by the Engineering and Physical Sciences Research Council of the United Kingdom, with the goal of bringing together the wave structure interaction community to share ideas and developments. This study utilises two computational methods, WEC-Sim and STAR-CCM+, to evaluate three prescribed focused waves on two taut-moored WEC-like buoys.…”