Simulating the effects of misalignment on impinging jet behavior

Rocket engineering and pharmaceutics share at least one common technology: impinging jet atomization. In this technique, two jets of fluid strike each other at a contact point, creating a liquid sheet that breaks up into small, polydispersed droplets.

Previous studies assumed the two jets hit each other in perfect alignment, but this assumption did not often reflect reality. Zhang et al. developed a numerical method to simulate misaligned impinging jets.

The authors found the spray behavior of impinging jets is very sensitive to the alignment of the two impinging jets. Droplets formed due to misaligned jet impact show a nonmonotonic dependence on the level of misalignment, with improved spray performance and more spatially uniformly dispersed droplets occurring under moderately misaligned impingement.

The team attributes the improved atomization behavior of the misaligned jets to a lateral stretching effect, which causes vorticity generation and subsequent instability of the liquid-air interface on the wider side of the liquid sheet. At larger misalignment ratios, the stretching effect suppresses the liquid sheet’s disintegration, which results in a higher wave frequency and less energetic mode.

“The deviation of jet impingement caused by a large degree of misalignment would substantially influence the transfer between kinetic energy and surface energy, which alters the jet atomization and subsequent combustion performance,” co-author Kun Wu said.

To obtain their results, the team employed Gerris, an open-source software that numerically predicts fluid flow, utilizing volume-of-fluid method with adaptive grid refinement to solve for fluid motion at various operating conditions.

Future work will quantitatively address the effects of viscosity, jet flow speed, surface tension, and other geometrical parameters.

Source: “Atomization of misaligned impinging liquid jets,” by Chenwei Zhang, Zhenyu Zhang, Kun Wu, Xi Xia, and Xuejun Fan, Physics of Fluids (2021). The article can be accessed at https://doi.org/10.1063/5.0061981 .