Single-particle approximation. Left panel: the temporal evolution of 3D distance (in Schwarzschild radii); the orbital parameters are set consistent with the G2/DSO in Galactic centre. Different particle (dust grain) sizes are considered, taking into account the effect of gravity and the hydrodynamical drag exerted by the ambient medium. Right panel: the corresponding velocity as a function of time. Hydrodynamical drag acts more efficiently on particles of larger size, causing their rapid in-spiralling and accretion onto the central black hole.