Modeling and simulation of fluid interactions with bluff body for energy harvesting application

This paper presents the study of modeling and simulation of fluid flow and bluff-body interactions in different fluid velocity in order to investigate the vortex induced vibration phenomena for energy harvesting application. The Strouhal number for two bluff-bodies is analyzed to identify the right bluff-body for optimized cantilever based energy harvester design. From vibration based energy harvesting standpoint, it is important to predict the frequency of vibrations at various fluid speeds and thereby identify the desirable resonances between the vibrations of bluff body structure and the vortex shedding. This study employs the use of COMSOL-multiphysics computational fluid dynamics software using the fluid structure interaction module. A Fast Fourier Transformation (FFT) in Matlab is performed on stationary bluff bodies lift force oscillation yielding the frequency of vortex shedding by taking the inverse of the difference between the time periods for each vortex pair. The main motive here is to seek a higher synchronized region of frequencies for the oscillation amplitudes for a range of fluid velocity and to calculate the lift and drag coefficients. The wake velocity profile is used to determine lift oscillation and calculate vortex shedding frequency for different Reynolds numbers. From two-dimensional, transient incompressible fluid flow simulation it is found that D-shaped bluff body has a comparatively higher lifting force than the cylinder-shape, suitable for optimized cantilever based energy harvester design in terms of a wide-range of lock-in.