Large-eddy simulation of coaxial powder flow for the laser direct deposition process

We conduct a large-eddy simulation with Lagrangian particle tracking to study the coaxial powder flow for the laser direct deposition process. To our knowledge, this is the first numerical study in which the high-fidelity, eddy-resolving simulation approach is applied to this process. Via the eddy-resolving simulations, we show the instantaneous flow structures and the associated turbulent quantities in great detail during the development of the transient state. We examine the effect of the flow on the particles and the resulting distributions of particle positions on various horizontal planes. Moreover, we demonstrate how the particle velocities affect the particle temperatures. On assessing three settings of initial particle distributions, we find that the simulation assuming a parabolic distribution for particle velocities gives good predictions of particle velocities and temperatures that are consistent with experimental data. Finally, we examine the effect of a substrate by moving the bottom boundary to the point of intersection of the particle streams. We find that due to increased flow dissipation, the substrate raises the location of the interaction point by approximately 10%. Moreover, the resulting reduction in particle velocity slightly increases the particle temperature. These differences can lead to a quite different distribution of the powder stream and have a significant impact on the mass and energy balance of the cladding model depending on the spot size of the laser beam and powder stream. ? 2021 Author(s).