Laboratory testing the Anaconda

Abstract

Laboratory measurements of the performance of the Anaconda are presented, a wave energy converter comprising a submerged water-filled distensible tube aligned with the incident waves. Experiments were carried out at a scale of around 1 : 25 with a 250 mm diameter and 7 m long tube, constructed of rubber and fabric, terminating in a linear power take-off of adjustable impedance. The paper presents some basic theory that leads to predictions of distensibility and bulge wave speed in a pressurized compound rubber and fabric tube, including the effects of inelastic sectors in the circumference, longitudinal tension and the surrounding fluid. Results are shown to agree closely with measurements in still water. The theory is developed further to provide a model for the propagation of bulges and power conversion in the Anaconda. In the presence of external water waves, the theory identifies three distinct internal wave components and provides theoretical estimates of power capture. For the first time, these and other predictions of the behaviour of the Anaconda, a device unlike almost all other marine systems, are shown to be in remarkably close agreement with measurements.

A linear numerical model for analysing the hydroelastic response of a flexible electroactive wave energy converter

“…Thus the model is not suitable for prediction of the power performance of a full scale device. Finally, quantitative agreement for the wave components is not very good in [4]. This is an issue for the SBM S3 WEC because power absorption occurs at the EAP rings which are distributed along the tubes.…”

“…Distensibility and losses were calibrated against the experiments. In [4], the proposed model is more comprehensive. It takes into account the boundary conditions and the power take-off.…”

“…Theoretical one-dimensional models for the dynamic response of the Anaconda WEC have been proposed in [9] and in [4]. In [9], the theoretical model predicts that the bulge wave amplitude grows linearly along the tube.…”

“…Secondly, the longitudinal tension is not taken into account in the models of the Anaconda WEC. In [4], it is neglected because it was found that it has a small effect on the distensibility. For the SBM S3 WEC, we found that it is critical for matching the boundary conditions for the tube section (no deformations at both ends of the tube) and for achieving good agreement between experimental and predicted eigenperiods.…”

“…Errors on the amplitudes of the wave components would transfer directly to errors of the same order of magnitude in power absorption performance. Therefore, to assess and optimize the performance of the SBM S3 device, one needs a model that rectifies the deficiencies of the models of [9] or [4], which is the primary aim of this study. The proposed mathematical and numerical model is described in sections 2 and 3.…”