Effect of angle of attack on an optimized vortex induced vibrated energy harvester: A numerical approach

A two-dimensional numerical study of flow induced vibration is reported in this paper to investigate flow over a semi-cricular D-shaped bluff body oriented at different angles-of-attack to determine an optimized design for energy harvesting. Bluff body structure governs fluid streamlines; therefore obtaining a suitable range of “lock in frequency” for energy harvesting purpose is dependent on refining and optimizing bluff body’s shape and structure. A cantilever based novel energy harvester design incorporates the suitable angle-of-attack for optimized performance. This optimization was done by performing computations for 30°, 60° and 90° angles-of-attack. The frequency of vibration of the body was calculated at different Reynolds Number. A Fast Fourier Transformation yielded frequency of vortex shedding. From the wake velocity profile, lift oscillation and frequency of vortex shedding is estimated. Strouhal numbers of the body were analyzed at different angles-of-attack. A higher synchronized bandwidth of shedding frequencies is an indication of an optimized harvester design at different Reynolds number. The ‘D’ shaped bluff bodies (with angle of attack of 30°,60° and 90°) are more suitable than that of cylindrical shaped bluff bodies. The research clearly stated that, bluff bodies shape has a prominent influence on vortex induced vibration and semicircular bluff body gives the highest vibration or energy under stated conditions.