Large-eddy simulation of vortex dynamics in transverse jet under combustor-like swirling conditions

This numerical investigation employs large-eddy simulation (LES) to systematically resolve jet-in-crossflow (JICF) phenomena with progressively increased geometric complexity, specifically targeting the aerodynamic characteristics of aero-engine combustor dilution zones. Through a staged approach beginning with fundamental flow mechanisms and advancing toward realistic configurations, the authors establish a methodical framework for isolating dominant flow physics. The study focuses on formation mechanisms, evolutionary dynamics of dominant coherent structures, and their consequential impacts on flow transport properties. Validation of the numerical framework was first performed using the canonical unilateral-jet configuration under uniform crossflow, confirming the LES methodology's capability to capture essential JICF vortex dynamics. Subsequent bilateral jet simulations revealed alternating shear-layer vortex shedding modulated by jet-to-jet interactions. Crucially, boundary-layer-free simulations demonstrated that wake vorticity originates not exclusively from crossflow boundary layer separation but also through interacting mechanisms: jet shear-layer instabilities and crossflow momentum defect regions collectively generate vertical vorticity components, ultimately coalescing into upright spiral vortices via merging co-rotating vortex pairs. For swirling crossflow conditions emulating combustor mainstream flows, the imposed strong streamwise vorticity fundamentally altered jet penetration dynamics. Swirl-induced spiral structures and vortex breakdown mechanisms dominated the flow reorganization, creating intensified three-dimensional turbulence. Quantitative mixing analysis revealed that swirl-driven flow reorientation coupled with fine-scale turbulence from vortex breakdown enhances turbulent scalar transport compared to non-swirling counterparts. These findings establish critical insights for modeling combustor-relevant JICF interactions while providing design guidelines for dilution zone optimization through controlled vortex manipulation.