Single and collective fiber dynamics in confined microflows
In this thesis, we studied the transport of single fibers and suspensions of fibers in microfluidic geometries. This collaboration work between Schlumberger and ESPCI-PMMH was motivated by the use of fibers in lost-circulation curing fluids in the oil industry. In this context where fibers are closely interacting with the flow boundaries, the roles of the geometry, flexibility and concentration of fibers as well as the flow geometry need to be understood. We created a microfluidic model system, integrating in a single experiment the fabrication and the flow of tailor-made fibers, using two different techniques. This new experimental system allows us to independently investigate the effect of all flow parameters. An in situ measurement of their mechanical properties is developed. Experimental and numerical work aims at understanding the transport of an isolated fiber in the Darcy flow, depending on its orientation and confinement. We show that the interactions of the fiber with the lateral borders of the microfluidic channel can lead to regular oscillations of the fiber. The collective dynamics of higher concentration of fibers is investigated when forcing them through a restriction in the microchannel. In particular, we address the question of the role of the orientation of the fibers on the clogging of the restrictions and the formation of fiber clusters upstream of the restriction.