Euler/Lagrange calculations of turbulent sprays: The effect of droplet collisions and coalescence

The Euler/Lagrange approach is a powerful numerical tool for the prediction of polydisperse two-phase flows. In the present article this method is app lied to the calculation of spray evolution by taking into account the two-w ay coupling between the phases, i.e., the gas and droplet phases, and dropl et evaporation. Moreover, a new stochastic droplet-droplet collision model based on the kinetic theory of gases Has developed. The model takes into ac count grazing and coalescing collisions, which are found to be very importa nt even for the low-speed turbulent spray considered. For validating the numerical results with regard to the spray evolution and the effects of droplet coalescence, detailed experimental studies Here per formed for two hollow-cone spray nozzles. In order to provide the required information concerning the spray characteristics sufficiently resolved, Le. , gas velocities, droplet size distributions, droplet mass fluxes, and drop let velocities, phase Doppler anemometry was applied. The comparison of measurement and prediction showed excellent agreement for the profiles of the mean properties of both phases and the local droplet s ize distributions and size-velocity correlations. Moreover, the calculation s revealed that the frequently observed increase of the integral droplet Sa uter mean diameter along the spray is due mainly to coalescence, while the impact of droplet evaporation is of minor importance.