Enhancing bladeless wind turbine performance using rear plates and diffusers through numerical fluid dynamics analysis

This study develops a novel Bladeless Wind Turbine (BWT) concept that augments a 2D oscillating cylinder (diameter D₂) with a rear plate and a diffuser assembly (inlet shroud, straight diffuser section, and flat flange), with and without a flange, to enhance aerodynamic performance. Unsteady laminar flow simulations are performed at a Reynolds number of Re = 185, corresponding to a free-stream velocity of 0. 27 m/s, using a validated Computational Fluid Dynamics (CFD) framework in ANSYS Fluent. A clean oscillating cylinder without any attachments is adopted as the baseline configuration for comparison. The novel contribution of this study lies in the first systematic parametric CFD investigation of rear plates, tapered plates, and flanged diffuser assembly applied specifically to a vortex-induced vibration–based BWT. The CFD framework is established, including a mesh-independence study and validation against four benchmark oscillating-cylinders from the literature. A parametric campaign (> 55 simulations) explores rear-plate length (L = 0. 5 - 1. 5 D₂), thickness (t₏=0. 01-0. 2 D₂), and taper (0. 5-2 t₏), as well as diffuser and flanged-diffuser assembly configurations. Performance is assessed via the maximum lift coefficient amplitude and vortex shedding frequency, which are directly related to the oscillation energy available for power extraction in vortex-induced vibration-based energy harvesters. Results show that a plate length of L{D₂}=1 maximizes lift, while decreasing the plate thickness (t₏{D₂}) increases lift amplitude; the best performance occurs at very thin plate (≈0. 01 D₂), achieving maximum lift coefficient amplitude. Compared to the clean oscillating cylinder, an optimal rear-plate design can increase the lift coefficient amplitude by approximately 157%, while maintaining a favorable shedding frequency. The highest performance is achieved when a concave rear plate is combined with a flanged diffuser assembly, where the maximum lift coefficient reaches CL ≈ 4. 5, corresponding to an enhancement of approximately 585% relative to the clean fixed-cylinder baseline. The findings highlight the significant role of rear plate and diffuser assembly designs in enhancing BWTs aerodynamic performance.