Session: 03-06 Fluid-Structure Interaction

Paper Number: 86824

86824 - Effect of the Macroscale on the Dynamics of a Slender Flexible Cylinder in Cross-Flow 

In this paper, we analyze preliminary results on how the turbulence generated from a passive grid located at different distances from a slender flexible cylinder (L/D= 120) affects its flapping dynamics. In a previous work, the effect turbulence intensity had on the dynamics of a flexible slender cylinder was studied by employing upstream grids of different porosities. No attempt was made to alter the macroscale of turbulence. The present study is a follow-up work which focuses on how the turbulence macroscale alters the flapping dynamics of the cylinder in a wind tunnel. In order to manipulate the macroscale of turbulence, a passive grid was placed at five different upstream locations with respect to the cylinder. We recorded the motion of the cylinder via a high-speed camera while the cylinder was exposed to wind speeds which were increased and then decreased in gradual steps. Furthermore, non-linear analysis of the data is used to determine whether the filaments enter a quasi-periodic motion, or chaotic motion, showing that small amplitude flapping is characteristic of random motion, while large-amplitude flapping is characteristic of quasi-periodic motion. Our results show that the turbulence macroscale modification has an effect on the critical velocity for the onset of flapping motions which remain two-dimensional. Independent of the macroscale, after the maximum peak-to-peak amplitude is reached at a certain flow speed, further increases of flow speed the peak-to-peak amplitude reduces until the cylinder transitions into chaotic three-dimensional motions.

Presenting Author: Felipe Condo Escuela Superior Politecnica del Litoral (ESPOL)