Up to now, we have focused on the description of particle dynamics while the fluid flow characteristics were calculated separately. In that sense, the fluid flow was treated as unaffected by particles and, since only the actions from the fluid to the particles are addressed in this approach, this is referred to as one-way coupling. Conversely, when particle effects on the fluid need to be considered in the fluid-phase description, we are dealing with two-way coupling. Two-way coupling involves two specific effects. The first one is the volumetric fraction occupied by the particles, \(\alpha _{\mathrm {p}}\) and the corresponding volume fraction of the fluid \(\alpha _{\mathrm {f}}\) (with \(\alpha _{\mathrm {f}}=1-\alpha _{\mathrm {p}}\) ) which may have to be included in the formulation of the governing equations. The second specific effect is the exchange of mean momentum and kinetic energy from particles to the fluid flow, which can become as important as exchanges between different parts of the fluid flow itself. In this chapter, we concentrate on this second effect and analyze the source terms accounting for these exchanges and their consequences on the stochastic particle dynamical model.