Extreme Wind Effects on Thin-Shell Hypar Kinetic Umbrellas for Coastal Defense Applications

Abstract

Anthropogenic climate change will cause an increase in coastal flooding in future years, creating a need for storm surge barriers. Traditional storm surge barriers have various drawbacks. Consequently, thin-shell hyperbolic paraboloid (hypar) kinetic umbrellas have been proposed as innovative storm surge barriers, with the goal of mitigating drawbacks of traditional barriers. This thesis uses wind tunnel testing on model hypar kinetic umbrellas in order to investigate how different forms of warping and aspect ratios interact with extreme wind loading. Firstly, the validation of the wind tunnel was conducted, by demonstrating a constant velocity profile and similarity of results when compared to theoretical values of coefficients. Furthermore, comparisons were made with results from a wind tunnel twice its size at the University of Oviedo. Secondly, the effects of warping and aspect ratio on aerodynamic coefficients were investigated. It was observed that larger warpings resulted in higher drag and moment coefficients at positive angles, resembling a parachute-like effect when wind blows into the umbrella. Conversely, at negative angles, larger warpings led to smaller drag and moment coefficients. Furthermore, for umbrellas in less-deployed positions (smaller angles), increased warping correlated with higher lift coefficients, whereas in more deployed positions (larger angles), higher warping correlated with lower lift coefficients. Similar patterns were observed for the flat plate model across fully deployed and undeployed positions. Higher aspect ratios were found to yield higher drag, lift, and moment coefficients compared to lower aspect ratios.