Experimental Analysis of Passive Bristling in Air to Enable Mako-Shark-Inspired Separation Control

Published on
08. June 2020

Experimental Analysis of Passive Bristling in Air to Enable Mako-Shark-Inspired Separation Control

Sean P. Devey, Amy W. Lang, James P. Hubner, Jackson A. Morris, Maria L. Habeggar

ABSTRACT:

Water tunnel studies have demonstrated that the skin of the fast-swimming shortfin mako shark (Isurus oxyrinchus) exhibits a passive method to limit flow separation. Limiting flow separation with such a mechanism could lead to reductions in pressure drag and increases in thrust and maneuverability for man-made systems as well as sharks. The flow control mechanism is enabled by the passive bristling of mako denticles. This paper describes initial efforts to realize the extension of the previous work in water to flows in air. A wind tunnel test of a mako skin-covered airfoil found no evidence of flow control. A benchtop study in air has determined that denticle bristling requires dynamic pressures over an order of magnitude greater in air than in water. Evidence suggests that this difference is caused by surface tension on the mako skin, which must be kept moist to prevent stiffening of the dermis. A first-generation mechanical model has been fabricated to mimic mako skin without these complicating moisture factors. The model achieved denticle bristling in air at similar dynamic pressures as real mako denticles in water, demonstrating that the limitations of real skin do not extend to mechanical models of mako skin and suggesting a path forward for future studies of this mechanism in air. An improved model has been integrated into the upper surface of an airfoil with wind tunnel testing planned.

AIAA Aviation 2020 Forum, DOI 10.2514/6.2020-2768

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