Mesoscopic Turbulence in Exotic Active Emulsions

Constituents of active matter inject energy in their surroundings, on scales much smaller than the system size, thus keeping the system far from thermodynamic equilibrium. Many examples of active matter evolve in the low Reynolds number regime, such as suspensions of bacteria or microtubules bundles. It is somehow surprising that this kind of systems exhibit a behavior reminescent of inertial turbulence.

In this work we present results of an in silico study for a binary fluid, made of a polar active component and an isotropic passive solvent in presence of a surfactant favouring emulsification of the two phases. The present model allows for the confinment of the turbulent behavior by triggering the typical size of active domains, i.e. the characteristic lengthscales of energy injection. We show that energy spectra exhibit power-law scaling in the high-wavenumber regime, only in a peculiar region of the parameter space. In particular exponents exhibit a strong dependence both on the active fraction and on the strength of active doping. These features arise due to a non-trivial hydrodynamics coupling between the liquid-crystal phase and the underlying fluid, thus causing the transfer of energy between different lengthscales.