The wave energy sector has made and is still doing a great effort in order to open up a niche in the energy market, working on several and diverse concepts and making advances in all aspects towards more efficient technologies However, economic viability has not been achieved yet, for which maximisation of power production over the full range of sea conditions is crucial Precise mathematical models are essential to accurately reproduce the behaviour, including nonlinear dynamics, and understand the performance of wave energy converters Therefore, nonlinear models must be considered, which are required for power absorption assessment, simulation of devices motion and model-based control systems Main sources of nonlinear dynamics within the entire chain of a wave energy converter - incoming wave trains, wave-structure interaction, power take-off systems or mooring lines- are identified, with especial attention to the wave-device hydrodynamic interaction, and their influence is studied in the present paper for different types of converters In addition, different approaches to model nonlinear wave-device interaction are presented, highlighting their advantages and drawbacks Besides the traditional Navier-Stokes equations or potential flow methods, ‘new’ methods such as system-identification models, smoothed particle hydrodynamics or nonlinear potential flow methods are analysed

/pdf/mathematical-modelling-of-wave-energy-converters-a-review-of-26x5med31l.pdf

Mathematical modelling of wave energy converters: A review of nonlinear approaches

This paper presents the results of an experimental investigation of the complete sequence of sediment behaviour beneath progressive waves. The sediment was silty with d50 = 0.060 mm. Two kinds of measurements were carried out: pore-water pressure measurements (across the sediment depth), and water-surface elevation measurements. The process of liquefaction/compaction was videotaped from the side simultaneously with the pressure and water-surface elevation measurements. The video records were then analysed to measure: (i) the time development of the mudline, (ii) the time development of liquefaction and compaction fronts in the sediment and (iii) the characteristics of the orbital motion of the liquefied sediment including the motion of the interface between the water body and the sediment. The ranges of the various quantities in the tests were: wave height, H = 9–17 cm, wave period, T = 1.6 sec, water depth = 42 cm, and the Shields parameter = 0.34–0.59. The experiments reveal that, with the introduction of waves, excess pore pressure builds up, which is followed by liquefaction during which internal waves are experienced at the interface of the water body and the liquefied sediment, the sequence of processes known from a previous investigation. This sequence of processes is followed by dissipation of the accumulated excess pore pressure and compaction of the sediment which is followed by the formation of bed ripples. The present results regarding the dissipation and compaction appear to be in agreement with recent centrifuge wave-tank experiments. As for the final stage of the sequence of processes (formation of ripples), the ripple steepness (normalized with the angle of repose) for sediment with liquefaction history is found to be the same as that in sediment with no liquefaction history.

The sequence of sediment behaviour during wave-induced liquefaction

Near-shore swell estimation from a global wind-wave model: Spectral process, linear, and artificial neural network models

Experimental study of marine pipelines on unstable and liquefied seabed

Shiaw-Yih Tzang

Papers

Simulating typhoon waves by SWAN wave model in coastal waters of Taiwan

Laboratory flume studies on monochromatic wave-fine sandy bed interactions: Part 1. Soil fluidization

Unfluidized soil responses of a silty seabed to monochromatic waves

Laboratory flume studies on monochromatic wave-fine sandy bed interactions Part 2. Sediment suspensions

Parametric design methodology for maximizing energy capture of a bottom-hinged flap-type WEC with medium wave resources