Abstract: This paper investigates particle dynamics both inside and outside a Laser Metal Deposition nozzle of a Directed Energy Deposition processing head, i.e. a Laser Metal Deposition (LMD) nozzle, by way of high-speed imaging and particle tracking as well as through computer simulations that account for particle collision and van der Waals forces. It is shown that the particle accumulation phenomena observed experimentally with cohesive aluminium powders can be qualitatively reproduced numerically. It is also demonstrated that such computer simulations can yield the correct order of magnitude for particle velocities, which is rarely reported in the literature and usually unknown for any given LMD system. This work thus paves the way towards more accurate simulations of gas-particle flows in LMD nozzles, especially with cohesive powders.