Survivability of wave energy converters using CFD

Abstract

The survivability of Wave Energy Converters (WECs) in extreme waves is a critical issue faced by developers; typically assessed via small scale physical experiments with considerable uncertainties. Until recently, confidence in the ability of numerical tools to reproduce extreme wave events and their interaction with floating structures has been insufficient to warrant their use in routine design processes. In this work a fully nonlinear, coupled tool for simulating focused wave impacts on generic WEC hull forms is described and compared with physical measurements. Two separate design waves, based on the 100 year wave at Wave Hub and using the NewWave formulation, have been reproduced numerically as have experiments in which a fixed truncated circular cylinder and a floating hemispherical-bottomed buoy are subject to these focused wave events. The numerical model is shown to reproduce the wave events well with some inaccuracies observed in shallower water depths. The results for pressure and run-up on the cylinder surface, as well as the high-order free-surface behaviour, also compare well with experimental results. The floating buoy's motion and mooring load are reproduced exceptionally well showing that the tool presented here can be used to assess WEC survivability and complement existing physical modelling.

A Blind Comparative Study of Focused Wave Interactions with Floating Structures (CCP-WSI Blind Test Series 3)

“…The moments of inertia corresponding to the other two geometric axes, I xx and I yy are given relative to the CoM of each of the structures. Complimentary work involving Geometry 1 can be found in Hann et al (2015) and Ransley et al (2017). In all cases, the structure is taut-moored using the same linear spring mooring with a stiffness of 67 N/m and a rest length of 2.199 m. Table 2 gives some key parameters when the structure is at rest (z = 0 corresponds to the still water level).…”

A Wave Energy Converter Design Load Case Study

“…The grid shown in Figure 5 was attained with grid resolution and convergence studies, including those reported in [2], an example of which is provided in Figure 6. The refined grid regions were established based on guidance from STAR-CCM+ [24], previously reported extreme sea state CFD studies [6,9,[25][26][27][28], accurately modeling the wave propagation, minimizing wave reflections, minimizing y+ on the RM3 model surface, and accurately resolving the velocity gradients around the model while keeping the total number of cells at a minimum. The final grid resolutions at the water surface and total number of cells for each case are reported in Table 3.…”

Experimental investigation of wave-in-deck impact events on a TLP model

“…(2011) and Deng et al (2016), Ransley (2015) has demonstrated that a similar approach can be applied to investigate the dynamic response of a floating moored structure. Such technique requires the time history of wave elevation at a point which is provided in this paper and in the Research Gate page of the first author 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 7 (Abdussamie, 2017).…”