Effect of microfibres placed at the front stagnation point of a circular cylinder on aerodynamics and wake flow

Abstract

We experimentally investigated the control effectiveness of circular cylinder flow and the mechanism of self-adaptive microfibres inspired by bird feathers. The nylon wires were placed at the front stagnation point of a circular cylinder at a Reynolds number of Re = 2.67×104. Surface pressure measurement was employed to analyse the unsteady aerodynamic forces around the circular cylinder, and a high-speed particle image velocimetry measurement system was used to visualise and analyse the wake flow structures. The results indicate that the nylon wires at a high length ratio L/D evidently suppress the Reynolds stress and turbulent kinetic energy, thus suppressing the fluctuating lift and mean drag forces of a circular cylinder. In addition, the nylon-induced vortex at high L/D values can inhibit the interaction of the original shear layers to moderate the von Kármán vortex street behind the cylinder. However, the control effect is limited at low L/D values because the nylon-induced vortex structures cannot reach the wake field and interact with the shear layer.