tumbling, buckling, snaking: dynamic transitions of semiflexible filaments in shear flow

Department: Mechanical & Aerospace Engineering
Faculty Advisor(s): David Saintillan

Primary Student
Name: Brato Chakrabarti
Email: bchakrab@ucsd.edu
Phone: 540-838-1590
Grad Year: 2020

Dynamics of polymeric fluids exhibit many counter-intuitive behaviors. The origin of these rich dynamics can be traced back to the complex conformations of polymer molecules in shear flow. Tumbling of rigid bodies in shear flow at low Reynolds number date back to the pioneering work of Jeffery. The effect of flexibility of the polymer chains has dramatic consequences in this classical problem. Here we study the dynamics of actin filaments in simple shear flow. Actin filaments are slender semi-flexible biopolymer, found in the cytoplasm of cells and they provide rigidity to the cell membrane. We model these inextensible filaments using Euler-Bernoulli beam and use nonlocal slender body theory (SBT) in the presence of Brownian fluctuations to probe their dynamics. We systematically explore the parameter space by varying the length of the polymer and changing the shear rate. We observe several different configurations ranging from periodic tumbling to nontrivial buckling due to compressive viscous forces. We have also come up with a analytically tractable theoretical model that allows us to explain one of the morphological transitions that was previously unexplained. Both our theoretical and simulation results are in great agreement with microfluidic experiments performed at ESPCI, France. Understanding the response of these polymers in shear flow will hopefully shed more light on the dynamics of polymeric fluids and also to some problems of recent interest, related to the dynamics inside the cell.

Industry Application Area(s)
Aerospace, Defense, Security | Life Sciences/Medical Devices & Instruments

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