My research interests lie broadly in the fields of Fluid Dynamics, Scientific Computing, Dynamical Systems, Applied Mathematics and Biophysics. In particular I am interested in developing theoretical and computational tools to study hydrodynamics of flexible slender structures. Problems involve understanding buckling instabilities of passive semiflexible polymers like actin filaments in flow, that are key to various cellular processes and dictate the rheological properties of suspensions. Another set of problems include bottom-up modeling of active micro-filaments like flagella or cilia that are driven out of equilibrium and understanding the role of hydrodynamics in emergent behavior or synchronization. My detailed simulations are often complemented by analytical solutions, scaling analysis, theoretical models from dynamical systems and by experiments done in close collaboration.

I have also worked on problems involving transport of active and passive particles in porous media, shear dispersion, mixing by chaotic advection and turbulence in active matter.

Brief descriptions of the projects and associated publications are given below. I prefer the arXiv version (if available) over the journal.


Shear-induced dispersion in peristaltic flow
Brato Chakrabarti, and David Saintillan
Physics of Fluids, 32 113102 (2020).

  • Invited: "Contributions from Early Career Researchers 2020"
  • Selected as a featured article

Theoretical study of Taylor dispersion in peristaltic pumping using generalized Taylor dispersion theory. We reveal the role of hydrodynamics, recirculation bubbles and entropic traps. Our findings have potential applications in micro scale transport and bio-mixing.


Trapping, gliding, valting: Transport of semiflexible polymers in periodic post arrays [arXiv:pdf]
Brato Chakrabarti, Charles Gaillard, and David Saintillan
Soft Matter, 16 5534 (2020).

We study transport of Brownian polymers in structured 2D lattices in presence of a pressure driven flow. Depending on several geometric parameters and polymer sizes we identify distinct modes of transport and study them using dynamical systems theory. These modes can be leveraged to design chromatographic devices that are able to sort polymers based on their lengths.


Flexible filaments buckle into helicoidal shapes in strong compressional flows [arXiv:pdf]
Brato Chakrabarti, Yanan Liu, John LaGrone, Ricardo Cortez, Lisa Fauci, Olivi du Roure, David Saintillan, and Anke Lindner
Nature Physics, 2020.

When flexible filaments experience strong compressive force, it buckles in 3D helicoidal conformations even in entirely planar flows. We elucidate this instability using experiments, simulations, scaling theory and weakly-nonlinear stability analysis. Our theory explains for the first time why coiling and helical morphologies are generic in strain dominated flows.


Hydrodynamic synchronization of spontaneously beating filaments [arXiv:pdf]
Brato Chakrabarti, and David Saintillan
Physical Review Letters, 123 208101 (2019).

Using our previous model for spontaneous oscillations of filaments we study hydrodynamic phase synchronization in a pair of filaments with waveforms ranging from sperm to cilia and Chlamydomonas. Our computations reveal both inphase and anti-phase synchrony can emerge for asymmetric beats and elucidate the mechanism for phase slips due to biochemical noise.


Spontaneous oscillations, beating patterns and hydrodynamics of active microfilaments
Brato Chakrabarti, and David Saintillan
Physical Review Fluids, 4 043102 (2019).

We develop a geometrically nonlinear model of the flagellar axoneme that accounts for the stochastic kinetics of molecular motors and results in spontaneous oscillations. We capture the beating patterns of sperm, cilia and Chlamydomonas and analyze their hydrodynamics through reduced order models.


Transport and dispersion of active particles in periodic porous media [arXiv:pdf]
Roberto Alonso Matilla, Brato Chakrabarti, and David Saintillan
Physical Review Fluids, 4 043101 (2019).

The long-time transport of active Brownian particles flowing through a porous lattice is studied using generalized Taylor dispersion theory and Langevin simulations. The effects of motility, lattice geometry, and fluid flow on the asymptotic spreading of a dilute cloud of microswimmers are unraveled.


Morphological transitions of flexible filaments in shear flow [arXiv:pdf]
Yanan Liu*, Brato Chakrabarti*, David Saintillan, Anke Lindner, and Olivia du Roure
Proceedings of the National Academy of Sciences , 115 9438 (2018)
(* denotes equal contribution)

Through a combination of microfluidic experiments and detailed elastohydrodynamic numeical simulations accounting for Brownian fluctuations we study dynamics of single actin filaments in shear flow and characterize their various dynamical regimes from tumbling to buckling and snaking. Analytically tractable reduced-order theoretical model is developed to elucidate the unexplained mechanism for the transition to snaking.


Catenaries in viscous fluid [arXiv:pdf]
Brato Chakrabarti, and James Hanna
Journal of Fluids and Structures, 66 490-516 (2016)

The classical catenaries are a one-parameter family of curves that don't change shape under translation and axial flow. Stick them in a fluid and they do, picking up four additional shape parameters. These solutions include towing, sedimentation, and other problems as subcases.

Under review

Signatures of elastoviscous buckling in the dilute rheology of stiff polymers [arXiv:pdf]
Brato Chakrabarti, Yanan Liu, Olivia du Roure, Anke Lindner, and David Saintillan

For fun!

Meso-scale turbulence in living fluids
Dense bacterial suspensions often demonstrate turbuelence like features. As a system driven inherently out of equilibrium, energy is continuously injected that drives a self-sustained vortex pattern. A variation of the classical Toner-Tu model along with Swift-Hohenberg theory can qualitatively capture this behavior with the governing equation resembling forced Navier-Stokes equation. I wrote a pseudo-spectral Matlab code in 2D for this 'active turbulence'.

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