Debasish Das

Sep 19, 2024 | link.aps.org | Pyae Hein Htet |Debasish Das |Eric Lauga

Flagellated bacteria are hydrodynamically attracted to rigid walls, yet past work shows a “hovering” state where they swim stably at a finite height above surfaces. We use numerics and theory to reveal the physical origin of hovering. Simulations first show that hovering requires an elongated cell body and results from a tilt away from the wall. Theoretical models then identify two essential asymmetries: the response of width-asymmetric cells to active flows created by length-asymmetric cells.

May 8, 2023 | link.aps.org | Debasish Das

Abstract We derive the flow field disturbance produced by point viscosity variations in a heterogeneous fluid when subject to a background flow while neglecting fluid inertia. The disturbance flow field is found to be identical to that generated by a force dipole called a stresslet.