Effect of sharp edges on the unsteady flow and aerodynamic performances of a Boxfish, towards bio-inspired low-drag bluff bodies

Abstract

Several studies have revealed that boxfishes, tropical fishes living in shallow waters, show exceptional aerodynamic performances despite their large volume and crosssectional area. These characteristics make the boxfish shape an interesting topic of study for drag optimisation of bluff bodies. This study focuses on the aerodynamic analysis of several mathematical shape representations of the boxfish. The effect of the edges is studied since they are responsible for the generation of vortices, which play a role in potentially manipulating the wake, resulting in an overall decrease in the drag coefficient. The effect of the sharpness or roundness of the edges on the aerodynamic performance is investigated. Aerodynamic coefficients are obtained numerically and experimentally for a range of Reynolds numbers between 3000 and 300000 and at pitch angle from −16◦ to +20◦.