Improving the Knowledge of High-Speed Liquid Jets Atomization by Using Quasi-Direct 3D Simulation

In this paper a quasi-direct solution of transient three-dimensional CFD calculations based on a finite volume approach has been adopted to simulate the atomization process of high velocity liquid jets issuing an injector-like nozzle. An accurate Volume-of-Fluid (VOF) method is used to reconstruct and advect the interface between the liquid and gas phases. An extended mesh which includes the injector nozzle and the upstream plenum has been considered in order to investigate accurately the effect of nozzle flow conditions on the liquid jet atomization. Cavitation modeling has not been included in the present computations. Two different mean injection velocities, 150 m/s and 270 m/s, respectively, have been considered in the calculations as representative of semi-turbulent and fully-turbulent nozzle flow conditions. The liquid-to-gas density ratio is kept fixed at 57. The calculations show that atomisation is directly linked to the temporally and spatially correlated turbulence of the liquid jet. The bulk flow perturbation and the relaxation of the boundary layer have been found to be the basic mechanisms that generate surface perturbations of the liquid jet.