Experimental investigation of a reduced-order model for a vortex-induced vibration wind converter

In this paper, the vortex-induced vibrations (VIV) of two bladeless wind energy converters (BWECs) are investigated through wind tunnel experiments, CFD-FEM simulations reduced-order model. BWECs consist of a blunt body attached to the tip of two flexible coaxial beams. In BWEC1, the blunt body is a truncated conic cylinder, whereas in BWEC2 it is a right cylinder. Due to periodic shedding vortices, the BWECs undergo vibrations that can be converted to electrical energy. An analytical reduced-order model is derived for the BWECs by incorporating a semiempirical model for the fluctuating aerodynamic lift coefficient into the Euler–Bernoulli theorem for the flexible support. The reduced-order model involves two principal assumptions: linear mode shapes for the aerodynamic lift force and a semiempirical model for the lift coefficient. The objective of the present research is to study and validate the accuracy of these two assumptions. To this end, wind tunnel experiments were accomplished to measure the tip displacement and CFD-FEM simulations were performed to obtain lift force distribution. Parameters of the reduced-order model are obtained using a genetic algorithm that minimizes the least squared error between the results of the model and the measurements of the experiments. To examine the assumptions of the reduced-order model, further CFD-FEM simulations are performed. The results of the CFD-FEM simulations confirmed the validity of the presumed lift force mode shapes. Moreover, it is justifiably inferred that the semiempirical lift model is the source of inconsistencies between the model and the wind tunnel experiments in high wind speeds of the post-lock-in region. In conclusion, the proposed reduced-order model is shown to be adequately accurate near the lock-in wind speed, which is the most significant working condition of the VIV energy harvesters.