Multi-scale statistics of turbulence motorized by active matter

Abstract

A number of micro-scale biological flows are characterized by spatio-temporal chaos. These include dense suspensions of swimming bacteria, microtubule bundles driven by motor proteins, and dividing and migrating confluent layers of cells. A characteristic common to all of these systems is that they are laden with active matter, which transforms free energy in the fluid into kinetic energy. Because of collective effects, the active matter induces multi-scale flow motions that bear strong visual resemblance to turbulence. In this study, multi-scale statistical tools are employed to analyze direct numerical simulations (DNS) of periodic two- (2D) and three-dimensional (3D) active flows and compare them to classic turbulent flows. Statistical descriptions of the flows and their variations with activity levels are provided in physical and spectral spaces. A scale-dependent intermittency analysis is performed using wavelets. The results demonstrate fundamental differences between active and high-Reynolds number turbulence; for instance, the intermittency is smaller and less energetic in active flows, and the work of the active stress is spectrally exerted near the integral scales and dissipated mostly locally by viscosity, with convection playing a minor role in momentum transport across scales.

arXiv commentAccepted in Journal of Fluid Mechanics (2017)

References in corpus (7)

• Spontaneous motion in hierarchically assembled active matter
• Meso-scale turbulence in living fluids
• Fluid dynamics of bacterial turbulence
• Velocity Correlations in an Active Nematic
• Stabilization of active matter by flow-vortex lattices and defect ordering
• Defect-mediated morphologies in growing cell colonies
• Onset of meso-scale turbulence in living fluids

Cited by in corpus (27)

• Active Turbulence
• Universal scaling of active nematic turbulence
• Turbulence and turbulent pattern formation in a minimal model for active fluids
• Perspectives on adaptive dynamical systems
• Twist-induced crossover from 2D to 3D turbulence in active nematics
• Topology of three-dimensional active nematic turbulence confined to droplets
• Vortex dynamics and Lagrangian statistics in a model for active turbulence
• Role of friction in multidefect ordering
• Cascade or not cascade? Energy transfer and elastic effects in active nematics
• Spectral energy analysis of bulk three-dimensional active nematic turbulence
• Inertia drives a flocking phase transition in viscous active fluids
• Scale-dependent statistics of inertial particle distribution in high Reynolds number turbulence
• Defect Line Coarsening and Refinement in Active Nematics
• Coexistence of active and hydrodynamic turbulence in two dimensional active nematics
• Scaling regimes of active turbulence with external dissipation
• The role of advective inertia in active nematic turbulence
• The nature of triad interactions in active turbulence
• Lagrangian Manifestation of Anomalies in Active Turbulence
• Self-generated gradients stabilize the hydrodynamic instabilities in active suspensions
• Chirality, anisotropic viscosity and elastic anisotropy in three-dimensional active nematic turbulence
• Dynamics of a Passive Droplet in Active Turbulence
• Activity induced isotropic-polar transition in active liquid crystals
• Coexistence of defect morphologies in three dimensional active nematics
• Vortex line entanglement in active Beltrami flows
• Reference map technique for Lagrangian exploration of coherent structures
• Nematic order condensation and topological defects in inertial active nematics
• Long-ranged velocity correlations in dense systems of self-propelled particles