Numerical Investigation of the Effect of Morphing on the Energy Harvesting Performance of a Flapping Foil

Abstract

Nowadays we have seen a drastic increase in the number of catastrophic natural disasters. According to a recent survey, only in 2022, the total number of natural disasters was 430, more than 1 per day for the entire year. One of the leading causes of this is the reliance of humans on non-renewable energy production methods, which is the leading cause of increase in greenhouse gases. The goal of this work is to introduce an alternative method using the latest research that uses the wind and flexible flapping wings to create energy. For this, a well understood case of NACA0015 was selected from the literature for the validation of the setup. Then the same setup was used to introduce the flexibility on the airfoil. Only active, sinusoidal morphing was used in this work. Initially, isolated cases were run for the leading and the trailing edge deformation, based on which, two further cases were selected for the combined motion of LE and TE. The parameters that were selected to vary were the morphing frequency and amplitude. The isolated cases results showed that there is a direct correlation between the amplitude and performance of the energy harvesting device. For the TE, the best case increases the efficiency from 33% for the rigid airfoil to 56%. The worst case for the trailing edge was still an increase from the rigid airfoil and went up to 45.1% efficiency. For the LE morphing cases, 2 cases led to a decrease in efficiency as compared to the rigid airfoil. But the best case from here still showed an improvement in efficiency with a value of 43.9%. Then the combined cases were run using the 2-DOF morphing scheme that allowed for independent motion of the TE and the LE. This allowed the LE and the TE to have separate morphing frequencies and amplitudes. The results in this case were for the best case, while still better than the rigid airfoil, were not better than the individual cases. The reason for that is perhaps a lack of phase difference between the motions of the TE and the LE. Also, the only type of motion used here was sinusoidal motion of the flapping and the morphing. For the future work, it is recommended that the limitations of this study are incorporated for further analysis of this phenomenon. Another thing that can be added is the energy required for active morphing of the airfoil, which is likely to result in smaller increases in the efficiency than the results found here.