This study examines how rotor-induced flow affects the distribution of particles impacting rotor blades by comparing 3D numerical simulations with simplified 2D sectional models. The analyisis is carried out on a wind turbine rotor and a small propeller under axial flow conditions, and adopts Reynolds-Averaged Navier-Stokes equations for the fluid phase and a one-way coupled Lagrangian approach for the dispersed phase. We demonstrate that conventional 2D multiphase flow models, commonly used in fields like ice accretion and erosion prediction, can fail to predict the 3D behaviour. These models typically assume that particles are in equilibrium with the rotor-induced flow, neglecting the upstream flow history. As an alternative, we also consider ballistic particles, unaffected by induction, based on the geometric velocity. To define the conditions under which the 2D approximation deviates from the 3D solution, we introduce an induction Stokes number, Stk_{ind}, and identify a critical range when Stk_{ind} is between ~0.1 and ~10. To address this discrepancy, we present a simple yet effective model that allows accurate 2D simulations, by incorporating the mutual effects of induced velocities, Stokes number and Reynolds number on particle trajectories.