Numerical Study of Cavitation Effects in Shock-Induced Tandem Droplet Breakup

In this work, we study how shock-induced heterogeneous cavitation affects the early interface dynamics during the aerobreakup of two nearby cylindrical water columns (tandem configuration). Simulations are carried out with the open-source solver ECOGEN, using a finite- rate pressure/temperature disequilibrium multiphase model, along with the volume-of-fluid interface treatment, and adaptive mesh refine- ment up to 800 cells-per-diameter. The setup reproduces a plane shock at Ms ¼ 2:4 acting on columns of diameter d0 ¼ 4:8 mm. The Weber number is We¼ 8:4 104, expressing the ratio of disruptive to restorative forces, while the Ohnesorge number is Oh¼ 1:7 10 3, corre- sponding to the shear-induced entrainment (SIE) regime. Comparisons with reference single-column data show good agreement for the inter- nal wave pattern and for the collapse-induced shock (CiS), located at 0:2 d0 from the downstream stagnation point. In the tandem case, waves reflected by the neighboring column weaken internal focusing, redistribute gas nuclei, and suppress a secondary CiS, breaking the symmetry seen for a single column. Vorticity fields indicate larger and more persistent peripheral structures, consistent with small shifts in SIE. Although phase change is not modeled, the simulated pressure minima reach values compatible with it at realistic tensile strengths, suggesting that early cavitation can seed morphology differences that may grow downstream. The results clarify a wave-mediated coupling in multi-body shock-droplet interactions and motivate follow-up studies with repeated shocks and explicit phase-transition modeling.