Study of the stability of jets and wakesapplication to the wake past slender bodies with blunt trailing edge

Abstract

Flow past bluff bodies is a typical configuration in many engineering applications, being it characterized by the massive separation of the boundary layer. This creates a wake that, under certain circumstances, undergoes unstable regimes. Such regimes entail transverse forces and periodic vortex shedding, and consequently, structural risks, e.g. vibrations and resonances. Despite of the interest, the sequence of regimes and bifurcations leading to turbulence in wakes behind slender bodies with blunt-trailing edge is not perfectly understood. This Thesis aims at shedding light on this issue for low Reynolds numbers, by characterizing (through experiments, numerical simulations and global stability analysis) the unstable regimes and bifurcations behind slender bodies with rounded nose, and study the effect of the aspect ratio. Furthermore, three passive control strategies for unstable wakes are applied: base bleed, rear cavities and body rotation.