Effect of adding a tail fin on the galloping behavior of a square prism: A computational study

Abstract

The emergence of flow energy harvesting as a means to harness energy to maintain low-power electronics gave rise to many new fundamental questions concerned with the galloping instability of prisms. Among such questions is that dealing with manipulating the trailing edge of a galloping prism to improve its overall energy capture characteristics. Specifically, since flow energy harvesters operate in environments where wind fluctuation is a common occurrence, the galloping energy harvester must rise to its steady-state amplitude in the shortest possible time while maintaining a large-amplitude steady-state response. In this paper, we develop a high fidelity computational model to investigate the effects of adding a Y-shaped tail fin to a square prism on its galloping response. In particular, we investigate how the addition of the fin affects the flow pattern around the prism, and how that influences the transient and steady-state galloping response of the harvester. Results demonstrate that, except for one extreme case involving a long tail fin with a large fork angle, the addition of the tail fin always increases the steady-state amplitude of the galloping response. As far as the rise time is concerned, there exists an optimal fork angle, which results in the shortest rise time for each tail length. This angle is 15° for a tail length of 1D ( D is the characteristic length of the prism), 0° for the 0.75 D tail fin, and 15° for the shortest tail length of 0.5D.