Date of Award

5-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Committee Member

Dr. Gang Li, Committee Chair

Committee Member

Dr. Mohammed Daqaq

Committee Member

Dr. Huijuan Zhao

Abstract

A body is identified as bluff when the surrounding flow is marked by a distinct separation at the edges of the leading face. Bluff bodies become unstable when sub-jected to fluid flow above some critical flow velocity. This instability causes the body to gallop. Galloping is a self-exciting phenomena which operates on bluff bodies with a substantial afterbody. It is the self-induced cross-wind oscillations of flexible struc-tures due to aerodynamic forces that are in-phase with the motion of the structure. In this unstable or galloping range, the energy fed into the body exceeds the energy dissipated by structural damping and thus, these conditions can be used to harvest energy. Galloping Flow Energy Harvester (GFEH) is a device that can be used to harness this excess energy. The galloping response of a body is characterized by the variation of transverse lift coefficient (CN ) with respect to angle of attack (α). Galloping response of bluff bodies with square and trapezoid cross-section has been investigated in this study using numerical simulations. It has been known that addition of a tail fin to a bluff body affects its galloping performance. The effects of adding tail fin of various lengths to bluff bodies of square and trapezoid cross section has been studied in this research. Further, this research provides a detailed explanation of flow behavior around the bluff bodies to understand the influence of cross-section and fin length on galloping response. Key flow characteristics that influence galloping were identified. Galloping response and flow behavior around square and trapezoid bluff bodies with different lengths of tail fin attached are compared and suggestions have been made to optimize the length of the tail fin to enhance lift performance.

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