Swirling gas–particle (droplet) flows are commonly encountered in gas-turbine combustors, cyclone combustors, and furnace burners. To better understand the flow behavior, many investigators did measurements, RANS (Reynolds-averaged Navier–Stokes) simulation, and LES (large-eddy simulation) of these types of flows. Most studies were done for weakly swirling gas–particle flows with swirl numbers less than unity. Experimental and numerical studies were done by the present author and his colleagues for PDPA measurements of swirling gas–particle flows with swirl numbers greater than unity, Reynolds-averaged two-fluid (Eulerian–Eulerian) simulation using k–ε–k_p and USM (unified second-order moment) two-phase turbulence models, and two-fluid LES using a two-phase sub-grid stress model. The measurement and simulation results give the two-phase time-averaged and RMS fluctuation velocities, and particle concentration distribution, showing the complex recirculation structures in the two-phase axial velocities and the Rankine-vortex structures in the two-phase tangential velocities, the anisotropic two-phase turbulence properties, and the effect of swirl number on the two-phase flow behavior. The simulation results show that the two-fluid approach using the k–ε–k_p and USM two-phase turbulence models are better than the Eulerian–Lagrangian approach for simulating swirling gas–particle flows