Dynamics of the energy concentration pipe in enhancing flow-induced vibration energy harvesting

The Energy Concentration Pipe (ECP) is a pipe structure attached to a bluff body that channels and concentrates incoming flow, providing a novel passive control strategy to enhance fluid–structure interaction and flow-induced vibration (FIV) energy harvesting. This study numerically investigates the influence of ECPs on structural dynamics, fluid dynamics, and internal energy transfer. The results show that the ECP significantly influences both the vibration and vortex shedding frequencies. At an outlet angle of 30°, the lock-in region is extended, whereas at 45° and 60°, a 1:3 lock-in transition to galloping is observed. The ECP intensifies near-wall Reynolds stresses, with high-stress regions expanding and moving closer to the body surface. This behavior is closely associated with energy transport within the internal channel. Flow visualizations indicate that the ECP absorbs additional incoming energy and redirects it into the wake, leading to intensified unsteady vortex structures. Under certain conditions, periodic flow reversal occurs at both the inlet and outlet, further enhancing energy exchange. The ECP achieves a maximum energy conversion efficiency of 0.416, representing a 54.5% improvement over the bare cylinder and demonstrating its effectiveness for passive flow control and energy harvesting.