In this paper, a numerical study using Direct Numerical Simulation (DNS) to understand the phenomenological behavior of gas flow and particles motion during low-pressure cold spraying has been studied. Observations of particles in-flight flow shows two features: a uniform particle jet over a short distance ahead of the nozzle exit and then, a progressive dispersion. These behaviors can be explained by the phenomenological supersonic flow computed by the DNS simulation. The transient DNS computation demonstrates that the gas stream starts to be unstable inside the nozzle with more turbulence as it moves towards the exit of the nozzle. The flow is self-oscillated along the flow direction and drives the motion of the Cu particles outside the nozzle. The zone of gas flow instability does correspond to the zone of experiment particle dispersion. The particles from the injection point inside the nozzle, are progressively deviated toward the upper wall of the nozzle until they reach the nozzle exit. Outside the nozzle, the particles form a straight jet over a certain distance that coincides with the zone of the experimental uniform jet. Then, the onset of deviation is evidenced by the DNS computation that exhibits a deformed jet. This phenomenon is caused by the irregular fluctuation of the gas that produces multidirectional motion and explains thereby the experimental dispersion of the particles. The computed virtual distribution of the particles along the flow direction shows the larger particles are prone to remain at the centreline zone of the jet, whereas finer particles are spread outside this central zone. At large distance away from the nozzle exit where wider dispersions of particles are experimentally observed, the DNS computation shows more dispersion of the fines particles.