  In this paper we propose a new modeling framework for large eddy simulations
(LES) of particle-laden turbulent flows that captures the interaction between
the particle and fluid phase on both the resolved and subgrid-scales. Unlike
the vast majority of existing subgrid-scale models, the proposed framework does
not only account for the influence of the sugrid-scale velocity on the particle
acceleration but also considers the effect of the particles on the turbulent
fluid flow. This includes the turbulence modulation of the subgrid-scales by
the particles, which is taken into account by the modeled subgrid-scale stress
tensor, and the effect of the unresolved particle motion on the resolved flow
scales. Our new modeling framework combines a recently proposed model for
enriching the resolved fluid velocity with a subgrid-scale component, with the
solution of a transport equation for the subgrid-scale kinetic energy. We
observe very good agreement of the particle pair separation and particle
clustering compared to the corresponding direct numerical simulation (DNS).
Furthermore, we show that the change of subgrid-scale kinetic energy induced by
the particles can be captured by the proposed modeling framework.
