a b s t r a c tA matrix method was developed by Kagemoto and Yue (1986) to compute interactions between multiple three-dimensional bodies subjected to linear water waves. The approach leads to a significant reduction in computational time versus the direct method, in which the boundary value problem is solved for all bodies simultaneously. An essential component of the theory is the so-called diffraction transfer matrix, a linear operator defined for each unique geometry. However, the diffraction transfer matrix is not a standard product of a linear wave computation, for one, because it is based around an unusual representation of incident waves, that is, as partial cylindrical waves. In this paper, a new method is presented to compute the diffraction transfer matrix from plane incident waves, which enables one to derive it from standard wave-body software or experiments. Additionally, a new linear operator -the force transfer matrix, is presented, which can also be determined by usual means. Herein, the interaction theory calculation is verified against direct method results from the linear wave-body software, WAMIT, and then applied to compute absorbed power and wave field effects on a medium-sized array in spectral seas and on a large farm of 101 wave energy converters in regular waves.

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Mocean Energy has designed a 100-kW hinged-raft wave energy converter (WEC), the M100, which has a novel geometry that reduces the cost of energy by improving the ratios of power per size and power per torque. The performance of the M100 is shown through the outputs of frequency-domain and time-domain numerical models, which are compared with those from 1/20th scale wave-tank testing. Results show that for the undamped, frequency-domain model, there are resonant peaks in the response at 6.6 and 9.6 s, corresponding to wavelengths that are 1.9 and 3.7 times longer than the machine. With the inclusion of power-take-off and viscous damping, the power response as a function of frequency shows a broad bandwidth and a hinge flex amplitude of 12-20 degrees per meter of wave amplitude. Comparison between the time-domain model and physical data in a variety of sea states, up to a significant wave height of 4.5 m, show agreements within 10% for average power absorption, which is notable because only simple, nonlinear, numerical models were used. The M100 geometry results in a broad-banded, large amplitude response due to its asymmetric shape, which induces coupling between modes of motion.

Wave energy converters (WECs) have been proposed that take advantage of spatially varying pressure differentials (PDs) in a wave field to drive a fluid flow. In order to accurately assess the pressure forcing on PD devices, physics-based relationships between major device parameters and device performance need to be determined. Herein, a transfer function is developed that relates horizontally oriented PD device configurations and wave conditions to the amount of pressure forcing available to the device. Investigation of the transfer function confirms intuitive expectation but also yields surprising results. The transfer function can be applied to a wave spectrum to create a pressure resource spectrum. By manipulating the device length and orientation, an optimal configuration can be found that maximizes the total harnessable pressure resource for a given wave condition or a wave climate. Optimal device lengths for directional seas are longer than those for nondirectional seas, and a wide range of suboptimal configurations yields a reasonable pressure resource. The pressure resource transfer function is a fundamental tool for understanding how horizontal PD WECs work and designing an optimal device.