Comparison of Empirical and Theoretical Computations of Velocity for a Cold Spray Nozzle

Abstract

Cold spray is a process whereby micron-size particles are accelerated to high velocity through entrainment in a gas undergoing expansion in a rocket nozzle and are subsequently impacted upon a surface. The impacted particles, which can be combinations of metals, ceramics and polymeric materials, form a consolidated structure that can be several centimeters thick. The characteristics of this structure depend on the initial characteristics of the metal powder and upon the impact velocity. Two-dimensional axi-symmetric computations of the flow through a converging, diverging nozzle were performed using the Reynolds-Averaged Navier-Stokes (RANS) code, Computational Fluid Dynamics++ (CFD++), on the Army Research Laboratory, Department of Defense (DoD) Supercomputing Resource Center (ARL DSRC) computers. Aluminum particles of constant diameter were injected at the entrance of a De Laval converging, diverging nozzle. The Eulerian Disperse Phase (EDP) capability in CFD++ was used for these simulations. The EDP model couples the dispersed phase with the fluid dynamics. In addition, onedimensional (1D), isentropic, gas-dynamic equations were solved for the same geometry and initial conditions. The results from the RANS computations and 1D calculation compared favorably, considering the difference in governing equations.