Numerical investigation on VIV energy harvesting of bluff bodies with different cross sections in tandem arrangement

The VIV (Vortex Induced Vibration) energy harvesting of two bluff bodies in tandem arrangement is investigated using two-dimensional numerical simulations in the spacing range of 2-50 diameters. Five groups of bluff bodies with different cross sections (Triangular prism, Square prism, Pentagon prism, Circular cylinder and Cir-Tria prism) are analyzed. To satisfy the needs of practical application, the damping ratio of the simulation set-up is high at 0.1076. The mass ratio is low at 0.93. The simulation results indicate that the VIV response of the upstream cylinder will be suppressed when the spacing is less than 5 diameters. Due to the wake effects, the motion of the downstream cylinder is largely affected by the upstream cylinder when the spacing is less than 35 diameters. In general, the Cir-Tria prism has better performance on energy harvesting (Maximum efficiency: 26.5%). The VIV response of the square prism is lower than all other bluff bodies. The circular cylinder is much more easily influenced by the wake. No matter what the cross section is, the amplitude ratio curve of the downstream cylinder changes regularly with the spacing and could be divided into 4 areas (Blocking Area, Encouraged Area, Disturbed Area and Recovery Area).