  We use three-dimensional direct numerical simulations of homogeneous
isotropic turbulence in a cubic domain to investigate the dynamics of heavy,
chiral, finite-size inertial particles and their effects on the flow. Using an
immersed-boundary method and a complex collision model, four-way coupled
simulations have been performed and the effects of particle-to-fluid density
ratio, turbulence strength, and particle volume fraction have been analysed. We
find that freely falling particles on the one hand add energy to the turbulent
flow but, on the other hand, they also enhance the flow dissipation: depending
on the combination of flow parameters, the former or the latter mechanism
prevails, thus yielding enhanced or weakened turbulence. Furthermore, particle
chirality entails a preferential angular velocity which induces a net vorticity
in the fluid phase. As turbulence strengthens, the energy introduced by the
falling particles becomes less relevant and stronger velocity fluctuations
alter the solid phase dynamics, making the effect of chirality irrelevant.
Moreover, comparing the time-history of collision events for chiral particles
and spheres (at the same volume fraction) suggests that the former tend to
entangle, in contrast to the latter which rebound impulsively.
