Aerodynamic design of a kinetic sculpture

Abstract

This paper presents a novel application of galloping to the design of a kinetic sculpture intended to represent the shape and motion of dune grass. This 35 m sculpture will consist of a flexible composite mast with an elliptical profile head, deliberately designed to generate slow but large-amplitude cross-wind galloping oscillations. The galloping characteristics of triangular, triform and cruciform head cross-sections have been investigated using static and dynamic wind tunnel tests, and modelled successfully using a simple energy balance method. The effect of yaw angle on galloping of three-dimensional shapes is much more significant than for 2D prisms, with the formation of leading-edge vortices from the swept edges tending to suppress galloping. This results in a desirable ‘self-furling’ feature, with the sculpture ceasing to move in high winds as the mast bands backwards. A full scale prototype has been successfully tested, in advance of the installation of a group of six Dune Grass sculptures on the sea front at Blackpool.