At the beginning of this study, the production process of hollow particles from the agglomerated particles is addressed analytically and numerically. The important parameters affecting this process, in particular, the initial porosity level of particles are investigated. In the analytical model, the possibility of a solid core existing in agglomerated particles is examined. In this model, a range of particle diameters (50 ?m ? D p0 ? 160 ?m) are considered. The numerical model employs the VOF technique for two-phase compressible flows. Simulation results of the analytical model indicate that the solid core diameter is independent of the initial porosity, whereas the thickness of the particle shell strongly depends on the initial porosity. In the next step, impact of a hollow droplet o a surface is simulated. An open-source, finite-volume based CFD code was used to perform the simulations, where appropriate sub-programs were added to handle the studied cases. Results showed that at high impact velocities ( ),the droplet splashed explosively. Compressibility effects result in a more porous splat, compared to the corresponding incompressible model. Moreover, the compressible model predicted a higher spread factor than the incompressible model, due to planetary structure of the splat. Key Words : Compressible flow, VOF model, Thermal spray coating, Hollow sphere particle, OpenFOAM, Solidification.
