Vortex structure analysis in the podded thruster using boundary data immersion method with verification and validation

This study investigates the vortex dynamics around the podded thruster through implicit large eddy simulation (ILES) coupled with the boundary data immersion method (BDIM). Numerical simulations are conducted using a Fortran-based solver, with verification and validation procedures demonstrating predictive reliability through minimal total error, and the validation error (|E|) remains below the validation uncertainty threshold (U_v). Meanwhile, three distinct vortex structures are identified: (1) the horseshoe vortex at the strut-pod junction, (2) the hairpin vortex at the top of the strut, and (3) the wake vortex system downstream of the propeller. The horseshoe vortex originates from boundary layer separation induced by an adverse pressure gradient. This structure undergoes stretching under the influence of rotational dominance. The hairpin vortex, evolving due to shear layer instability, progresses from vortex ring formation to self-induced uplift and multi-scale interactions, ultimately dissipating through turbulent bursting. The wake vortex system exhibits strong instability and turbulent breakdown, leading to rapid downstream deformation and energy dissipation.