Hybrid Rans-Les Computational Modeling Of Liquid Droplet Aerobreakup

  • ROSSANO, VIOLA (University of Campania Luigi Vanvitelli)
  • DE STEFANO, GIULIANO (University of Campania Luigi Vanvitelli)

Please login to view abstract download link

Despite its great importance, understanding the shock-induced aerobreakup phenomenon faces great challenges in experimental investigations due to the inaccessibility of direct observations. On the other hand, as computational resources reach the exascale, there is increased accessibility to finer resolved scales, enabling more precise simulations of engineering test cases. Nevertheless, the wide range of spatial and temporal scales typically encountered makes the direct numerical simulation (DNS) of this phenomenon practically impossible and most simulations are constrained to relatively low Weber (We) and Reynolds (Re) numbers. Unfortunately, higher We and Re are common in industrial applications, giving rise to fundamental instabilities during the process of droplet fragmentation, which need to be addressed. This way, further investigations employing advanced techniques are needed to overcome the above constraints- Recently, both large-eddy simulation (LES) and unsteady Reynolds-averaged Navier Stokes (URANS) methods have been applied for the numerical prediction of shock-induced droplet aerobreakup problems of engineering interest. In this study, two different hybrid RANS-LES models for the computational evaluation of liquid droplet aerobreakup are examined, namely, the scale-adaptive simulation (SAS) and the stress-blended eddy simulation (SBES). The proposed computational methods utilize the volume-of-fluid (VOF) technique for the interface capturing together with the discrete phase model (DPM) for the Lagrangian evolution of smaller liquid fragments. The numerical solver employs adapted dynamic grid technology, where the mesh is automatically refined at the transient gas/liquid interface, allowing for breakup simulations with affordable computational complexity. The various computational models are tested for different flow configurations in the shear stripping breakup regime. The alignment found between present results and reference data suggests a favorable correlation in terms of key integral features, including droplet morphology and dynamics, as well as sub-droplet size and velocity distributions. In fact, the present study provides a first demonstration of the high potential of hybrid RANS-LES methods for multiscale two-phase complex turbulent flows.