Effects of dissimilar wakes on energy harvesting of Flow Induced Vibration (FIV) based converters with circular oscillator

Abstract

In recent times, transverse Flow Induced Vibration (FIV) has emerged as a promising technique for energy harvesting from fluid motion. However, relatively low harnessed power and efficiency remain as major challenges. Although several studies on hydrokinetic energy harvesting of circular oscillators at the wake of similar cylinders are reported in the literature, their performance under the influence of an upstream body with dissimilar cross-section is still unexplored. In this study, the effects of sharp edge square and diamond wakes on the energy harvesting of downstream circular cylinders are investigated through combined experimental and analytical modelings. The effect of electromagnetic coupling on the performance of the system is examined by numerical solution of the coupled mechanical and electromagnetic equations. Semi-empirical models are employed to simulate the response of the circular oscillator at the optimum electromagnetic coupling coefficient. The results show that the dissimilar wake is capable of considerably increasing (around 200%) the mechanical power of the circular oscillator but, at the cost of lower efficiency at high flow rates. Multi Criteria Decision Making (MCDM) analysis is performed to identify the priority of the similar and dissimilar wakes in the energy harvesting improvement. Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) with subjective and Shanon’s entropy weight factors prove the overall advantages of the similar wake at close distances over the dissimilar upstream cylinder. The present study contributes to the appropriate implementation of the upstream interfering bodies as a method to increase the energy performance of the FIV harvesters.