Pair dynamics of active force dipoles in an odd-viscous fluid

Area of Science:

• Soft Matter Physics
• Active Matter
• Fluid Dynamics

Background:

• Active matter systems exhibit complex behaviors driven by internal energy conversion.
• Hydrodynamic interactions are crucial for collective dynamics in confined active fluids.
• Chirality and odd viscosity introduce non-reciprocal interactions in fluid systems.

Purpose of the Study:

• To investigate the lateral dynamics of two interacting active force dipoles in a 2D active chiral fluid.
• To analyze the influence of odd viscosity on the hydrodynamic interactions and particle trajectories.
• To elucidate the complex dynamics, including spiral and oscillatory behaviors, arising from nonreciprocal responses.

Main Methods:

• Modeling the fluid layer as a 2D compressible fluid with odd viscosity.
• Analytical derivation of the mobility tensor considering momentum decay and odd viscosity.
• Numerical computation of phase diagrams for particle dipolar angles.

Main Results:

• The particle pair exhibits spiral motion due to transverse flow induced by odd viscosity.
• Two types of oscillatory behaviors are observed when odd viscosity is large compared to shear viscosity.
• Circular trajectories are determined by the ratio of odd viscosity to force dipole magnitude.

Conclusions:

• Odd viscosity in active chiral fluids leads to nonreciprocal hydrodynamic interactions.
• These interactions result in complex dynamics, including spiral and oscillatory motions of active particles.
• The study highlights the significant role of nonreciprocity in the behavior of active matter systems.