Wave farm modelling of oscillating wave surge converters

Abstract

A mathematical model is described to analyse the hydrodynamic behaviour of a wave energy farm consisting of oscillating wave surge converters in oblique waves. The method is a highly efficient semianalytical approach based on the linear potential flow theory. Wave farms with a large number of such devices are studied for various configurations. For an inline configuration with normally incident waves, the occurrence of a near-resonant behaviour, already known for small arrays, is confirmed. A strong wave focusing effect is observed in special configurations comprising a large number of devices. The effects of the arrangement and of the distance of separation between the flaps are also studied extensively. In general, the flaps lying on the front of the wave farm are found to exhibit an enhanced performance behaviour in average, owing to the mutual interactions arising within the array. A random sea analysis shows that a slightly staggered arrangement can be an ideal layout for a wave farm of this device. The hydrodynamics of two flaps that oscillate back to back is also discussed.

Motion-resonant modes of large articulated damped oscillators in waves

“…The computational aspects of the numerical evaluation of the terms in Eq. (8) are detailed in Renzi et al (2014a) and Sarkar et al (2014).…”

“…It is assumed that the amplitude of the wave field is small with respect to the width of each device, as it happens in reality for most of the operational life of the system (Gallagher et al, 2013). Hence following the linearised theory of Renzi et al (2014a) and Sarkar et al (2014), the velocity potential Φ ′ (x ′ , y ′ , z ′ , t ′ ) must satisfy the Laplace equation…”

“…, M, where the Heaviside step function assures absence of flux through the foundation. Following Adamo and Mei (2005), Dias (2012, 2013a,b), Renzi et al (2014a) and Sarkar et al (2014), in Eq. (4) the flap thickness is considered immaterial for the calculation of the potential.…”

“…As mentioned in the Introduction, the flap-type absorber is the mathematical reference model for the OWSC, a large buoyant flap used for wave energy extraction in the nearshore environment Dias, 2012, 2013a,b;Renzi et al, 2014a). Only in-line configurations will be investigated in this paper, as loss of symmetry in small arrays of OWSCs is likely to be accompanied by a reduction in efficiency (Renzi et al, 2014a;Sarkar et al, 2014). The oscillators are set into motion by incident waves of amplitude A ′ I , period T ′ and angular frequency ω ′ = 2π/T ′ incoming along a direction which forms an angle β with the x ′ axis.…”

“…(4). This task can be accomplished by solving the following system of equations of motion for the oscillators in the frequency domain (Falnes, 2002;Mei et al, 2005;Renzi et al, 2014a;Sarkar et al, 2014):…”