Spontaneous aggregation and global polar ordering in squirmer   suspensions
  We have developed numerical simulations of three dimensional suspensions of active particles to characterize the capabilities of the hydrodynamic stresses induced by active swimmers to promote global order and emergent structures in active suspensions. We have considered squirmer suspensions embedded in a fluid modeled under a Lattice Boltzmann scheme. We have found that active stresses play a central role to decorrelate the collective motion of squirmers and that contractile squirmers develop significant aggregates. 
Francisco Alarc\'on and Ignacio Pagonabarraga
cond-mat.soft