Capturing the bi-stable asymmetry exchanges in the turbulent air wake of a simplified frigate using large eddy simulation

Turbulent air wake of a Simplified Frigate Ship (SFS2) model is simulated using wall-resolved Large Eddy Simulation. The wake behind the superstructure presents an asymmetric configuration for an otherwise symmetric free stream condition. Bi-stable characteristics of the wake have also been simulated as evidenced by asymmetric state switching events. The wake behind the stern also exhibits bi-stable switching and adapts an opposite asymmetric orientation to the wake behind the superstructure, as also observed experimentally. The resulting time-averaged flow fields for each bi-stable state reveal a differential flux formation around the upstream sides of the superstructure. The instantaneous wake fields also suggest a possible influence of flow structures developed around the upstream end of the superstructure to generate a particular asymmetric wake state downstream. •Turbulent wake behind a simplifed frigate model is simulated using RANS and wall-resolved Large Eddy Simulaton.•First study of bi-stable transients captured numerically behind both (superstructure and stern) steps of the Simplifed Frigate Ship (SFS2) model.•The state sampled fields for each bi-stable state reveal a differential flux formation around the upstream sides of the superstructure.•The instantaneous wake fields also suggest a possible influence of flow structures developed around the upstream end of the superstructure to generate a particular downstream asymmetric state.