Diffusion of active dimers in a Couette flow.

Area of Science:

• Fluid dynamics
• Active matter physics
• Biophysics

Background:

• Active dimers, composed of self-propelling and passive components, exhibit complex behaviors in fluid flows.
• Hydrodynamic interactions significantly influence the dynamics of suspended particles, especially in confined or sheared environments.

Purpose of the Study:

• To investigate the 3D dynamics and diffusivity of an elastic active dimer in a Couette flow.
• To analyze the role of self-propulsion speed and shear flow strength on dimer dynamics.
• To understand the influence of hydrodynamic interactions on active dimer diffusion.

Main Methods:

• Numerical simulations were employed to model the 3D dynamics of the active dimer.
• The study systematically varied self-propulsion speed and Couette flow parameters.
• Diffusivity was calculated to quantify the dimer's movement.

Main Results:

• Hydrodynamic interactions were found to be significantly enhanced when the dimer's self-propulsion effectively countered the shear flow.
• The magnitude of this enhancement increased with the relative size of the dimer's constituents.
• These findings suggest conditions under which the effects are experimentally observable.

Conclusions:

• Self-propulsion strength relative to shear flow is critical for enhancing hydrodynamic interactions in active dimers.
• The study provides insights into the factors governing the diffusion of active particles in complex flow fields.
• Results indicate the potential for experimental validation of these simulated dynamics.