Meeting Abstract
The morphology of shark skin denticles varies considerably over the body of individual animals, and also displays remarkable variation among species. However, the hydrodynamic functions of denticle pattern and spacing remain unexplored. In previous work, we used high-resolution micro-CT scanning to construct a three-dimensional model of shortfin mako (Isurus oxyrinchus) shark skin denticle. Based on this model we have designed and 3D printed flexible foils with different denticle patterns and spacings: (1) staggered overlapped, (2) linear overlapped, and (3) linear non-overlapped. These 3D printed shark skin models were then tested in water tank using a robotic flapping device that allowed us to either hold the models in a stationary position or move them dynamically. We swam the foils at a frequency of 1Hz with different heave amplitudes (from ±1 cm to ±3 cm) while measuring forces, torques, self-propelled swimming speed, and cost of transport (COT). Compared with a smooth control foil without denticles, we found that the foil with staggered overlapped denticles produced significantly faster swimming speeds with slightly increased COT. For instance, at a heave frequency of 1 Hz and amplitude of ±1 cm, swimming speed increased by 34%, while the cost-of-transport increased 8.7%. However, lower swimming speeds and higher COT than the smooth control was generated by foils with both linear overlapped and linear non-overlapped denticles. Quantitative hydrodynamic comparisons among 3D printed models provide a sophisticated experimental approach for understanding the considerable natural diversity of shark skin denticles both among species and on different body locations.
