Energy harvesting of two inverted piezoelectric flags in tandem, side-by-side and staggered arrangements

Abstract The flow-induced vibration characteristics and energy extraction performance of flexible inverted piezoelectric flags in a uniform flow are studied by using an immersed boundary-lattice Boltzmann method for Reynolds number of 100, mass ratio of 2.9 and non-dimensional bending stiffness of 0.26 which correspond to the maximum flapping amplitude for a single inverted flag. The coupled fluid-structure-electric dynamics of two inverted piezoelectric flags in the tandem, side-by-side and staggered arrangements is investigated to determine the effects of the piezoelectric parameters (α and β) on the dynamics of the flags and to quantify the energy harvesting performance. Simulations are conducted by varying the streamwise gap distance (Gx/L) from 0.1 to 3.2 and cross-stream gap distance (Gy/L) from 0.4 to 2.5. It is found that both the flapping amplitude and the frequency of the flags reduce as the piezo-mechanical coupling parameter (α) increases due to the damping effect, particularly in the tandem arrangement. The maximum electrical power coefficient ( C ¯ P ) is produced in the staggered arrangement at α = 0.5 , β (piezo-electric tuning parameter) = 1.5, G x / L = 1.4 and G y / L = 2.2 where the C ¯ P of the downstream flag is 0.042, 16% and 12.5% higher than that of the upstream flag and that of the single flag, respectively. The improvement in C ¯ P of the downstream flag is attributed to the increase in the kinetic energy of the fluid flow created by the upstream flag as a bluff body.