Marine current energy extraction through buffeting

Abstract

The research is an experimental study on the feasibility of marine current energy extraction through the phenomenon of buffeting. This phenomenon is a type of flow-induced oscillation of an elastic structure that is caused by the unsteadiness of the incoming flow. In order to prove the concept, a preliminary unit turbine model is designed working based on the buffeting phenomenon. The turbine model is an elastic structure, consisting of a rectangular flat plate located in a current flume. The elasticity is provided by attachment of four linear springs with equal rates (k) at the edges of the flat plate, to give an equivalent torsion spring rate. The unsteadiness is due to the wake of a bluff body located for this purpose in the upstream of the flat plate. The von Kármán street in the wake formed behind the bluff body induces oscillating moments in the flat plate which makes it to yaw with small angles of attack. The results demonstrate that one such system has the ability to extract hydrokinetic energy with efficiencies of up to 60%. The model tests results then are used to estimate the performance of the array of turbines, through the similarity analysis. Finally, a rough estimate of the manufacturing, installation and operation cost of the buffeting turbine subsea farm is presented.