The viscous flow past a prolate spheroid is always complicated and often three-dimensional, thereby fascinating scientists in fluid dynamics and aerodynamics. The objective of this paper is to investigate the asymmetric wake behind a 6:1 prolate spheroid at 45-deg angle of attack by means of Large-Eddy simulations(LESs). The LES was performed at a Reynolds number of 10000, based on the free stream velocity U0 and minor axis diameter D. Results in the paper were compared with the previous LES results for different Re. The simulation revealed that there was a pair of counter-rotating vortex in the near wake field, which developed from a pair of vortex sheet separating from the sides of prolate spheroid. The vortex broke and the coherence of vortex tube lost because of the influence of vortex shedding from the tip of the prolate spheroid and energy dissipation. The asymmetry could be observed evidently from several physical quantities, such as velocity, vorticity, pressure and side force. The results showed an obvious skew of vortex structure, the direction of which was random and could be explained by pitchfork theory. The comparison between near field and far field was present to show the development and features of the flow characteristics. The asymmetric wake should be given more attention as it may be detrimental to underwater vehicle performance and submarine maneuverability.

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