Aggregation of fibers by flows: structure, mechanics and formation of Aegagropilae
Date:
Tuesday, March 14, 2017 13:00 - 14:00
Speaker:
Patrice Le Gal (CNRS, Marseille)
Location:
Seminar Room, Lab Building East
Series:
Physical Sciences Seminar
Host:
Björn Hof
Contact:
SIX Rita
Fiber networks encompass a wide range of natural and man-made materials. The threads or fi laments from which they are formed span a wide range of length scales; from nanometers as in biological tissues and bundles of carbon nanotubes, to millimeters as in paper and insulation materials. The study of fi ber clustering of natural flocks could be useful for improving fabrication processes, such as in the paper and textile industries for instance. Here, we use the example of aegagropilae that are the remains of a seagrass (Posidonia oceanica) found on Mediterranean beaches. First, we characterize di fferent aspects of their structure and mechanical response which make possible to draw some conclusions on their formation process in particular by analysing the statistical distributions of size and mass of these balls. We show that these natural aggregates are formed in open sea by random aggregation and compaction of fibers which are held together by friction forces. Finally, we report results from two laboratory experiments, first on the behavior of a single fiber in a turbulent von Karman flow where we demonstrate that the conformations of flexible fibers in turbulence are analog to conformations of flexible polymers in a solvent and then on the aggregation of fibers by a Stokes drift in a wave-induced flow.