Delay or removal of aneurysm formation in the Anaconda wave energy extraction device

Abstract

Any distensible tube inflated beyond a critical pressure will experience aneurysm formation. The Anaconda wave energy device consists of a pressurised flooded tube, which when excited with an external incident wave of appropriate frequency, for the set inflation pressure, permits generation of internal bulge waves that provide the mechanism for more efficient wave energy extraction. The distensible tube must be designed to have structural integrity and to facilitate the bulge wave matching the incident wave. The bulge wave speed is governed by internal fluid density and tube distensibility. The latter is readily shown to be dependent upon volume–pressure gradient within the tube. With application of a displacement–pressure based finite element formulation the likelihood of aneurysm and its delay or avoidance can be investigated. The strain energy functions selected for use with the finite element analysis are the Yeoh and third-order Ogden model as these formulations have been previously shown by the authors to satisfy the required Maxwell equal area rule and provide the most consistent predictions when using different mixes of experimental stress-strain data. After summarising a representative set of known wave energy extraction devices, to appreciate how different Anaconda is, the paper looks at the extent and mode of deployment of an outer inextensible reinforcement to provide bulge waves of appropriate speed whilst also overcoming the onset of aneurysms within the Anaconda tube.