Multi-bluffbody Flow-induced Vibration Suppression And Energy Harvesting Based On Bi-directional Fluid-solid Coupling

The study of multi-bluffbodies flow-induced vibration(FIV)has been a hot topic of research in the field of fluidic vibrations,which are not only widespread in nature and engineering but also a double-edged sword,thus improving the theory of flow-induced vibration is of great importance to the energy and engineering fields.In this paper,we investigate the energy harvesting and vibration suppression of different systems from the perspective of multiple bluff bodies,in various forms of series-parallel and metamaterial arrangements.Firstly,the vibration characteristics of a series of bluff bodies of the same cross-section are investigated.The dynamic response of a series circular-section bluff body and a series square-section bluff body was investigated for different spacing and radius ratios.The results show that with the increasing spacing ratio,the series square cylinder system can effectively suppress vibration in the interval ofα=5.3-5.7 when 6≤U_r≤8.Subsequently,the effect of different radius ratios was investigated.It was found that the vibration of the downstream square cylinder shifted from vortex-induced vibration(VIV)to galloping as the radius ratio increased.Further this paper investigates the vibration characteristics of bluff bodies with different cross-sections when they are connected in parallel.The results show that the spacing ratio,reduced velocity and Reynolds number have a significant influence on the wake motion and dynamic characteristics of the coupled system.A single bluff body system with a square cross-section exhibits direct galloping without any vortex-excited vibration transitions.Subsequently,in a numerical study of the reverse wake-induced vibration(RWIV)of two circular cylinders in series,the Reynolds number was set at 150and the effect of varying the spacing ratio between 3 and 6 was simulated.It was found that the RWIV system exhibits a transition from galloping to VIV,which is an inverse phenomenon compared to WIV,and a transition between the two wake vortex shedding modes was also observed.Finally,a multi-bluff body arrangement of fluidic metamaterial structures suitable for FIV was investigated.Three 2D metamaterial structures were designed and investigated based on these findings,including four-interference,six-interference and eight-interference bluff body structures.It was found that the voltage output power of the three metamaterial structures was more significant than that of the single bluff body system.The four-interference cylindrical structure showed both a maximum output power of 2.4?W at U_r=5 and good suppression at 10≤U_r≤12.In the reduced radius comparison case,the dimensionless amplitude of the metamaterial scheme is still greater than that of the single bluff case,but no property of expanding the’locked-in’interval is found.In summary,the research in this paper has fully demonstrated the feasibility of metamaterial structures to improve the energy harvesting effect of FIV energy harvesters and to implement the vibration characteristics of multi-bulffbody FIV under different conditions,which is of great significance for engineering vibration suppression and energy harvesting research.