On the Influence of Nozzle-Generated Coherent Structures on the Primary Atomization of Fuel Jets

The application of a 3-phase VOF-LES solver [1] to the simulation of two transparent nozzle replicas is presented. The solver, implemented in the OpenFOAM Technology, is able to capture in-nozzle cavitation and fuel atomization near the nozzle exit. Simulations show that flow features are influenced by the sac and the hole geometry. It is found that the primary flow deviates in the sac, and that a secondary swirling flow generates. Depending on their importance, counter rotating vortices generates in proximity of the hole entrance. When the fluid pressure is about the saturation pressure, the flow cavitates and vortex strings are generated in newly formed vortex cores. Detailed flow unsteadiness and vortex pair instabilities change the instantaneous flow topology. No hydraulic flip is found in the tested real-size conical hole geometries. The nozzle flow features can be therefore related to the external flow results. The present work focuses on so-named “primary atomization” which is in fact related to cavitation collapse, liquid dispersion and interface wrinkling and breakup.