Forced and natural dynamics of a clamped flexible fiber in wall turbulence
Giulio Foggi Rota, M. Koseki, Riya Agrawal, Stefano Olivieri, Marco Edoardo Rosti
Abstract
We characterize the dynamical behavior of a clamped flexible fiber immersed in wall turbulence over a wide range of natural frequencies (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>f</a:mi><a:mi>nat</a:mi></a:msub></a:math>) by means of direct numerical simulations. Only two flapping states are possible: one where the fiber oscillates at the characteristic frequency of the largest turbulent eddies (<b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:msub><b:mi>f</b:mi><b:mi>turb</b:mi></b:msub></b:math>) and another where the natural structural response dominates. The former is obtained in the more flexible cases (<c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:msub><c:mi>f</c:mi><c:mi>nat</c:mi></c:msub><c:mo><</c:mo><c:msub><c:mi>f</c:mi><c:mi>turb</c:mi></c:msub></c:mrow></c:math>), while the latter in the more rigid ones (<d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:msub><d:mi>f</d:mi><d:mi>nat</d:mi></d:msub><d:mo>></d:mo><d:msub><d:mi>f</d:mi><d:mi>turb</d:mi></d:msub></d:mrow></d:math>). We observe that in the turbulence-dominated regime, the fiber always sways at a frequency proportional to the largest scale of the flow, regardless of its structural parameters. The hindrance of the clamp to the wall prevents the synchronization of the fiber with turbulent eddies of comparable size. Published by the American Physical Society 2024