Symmetry breaking in annular jets with different blockage ratio

Abstract

Abstract We perform direct numerical simulations of the annular laminar jet flows for two inner-to-outer diameter (blockage) ratios br = d / D = 0.5, 0.9 in the range of the Reynolds number based on the bulk velocity inside the nozzle and its outer diameter Re = 200 – 400. In spite of the axisymmetric formulation, asymmetric states are observed for moderate and high Re. A gradual increase of the Reynolds number allow building a regime map. The symmetry-asymmetry transition Reynolds number decreases with the increase of br, while the steady-unsteady transition Reynolds numbers are close for both br. The degree of asymmetry increases with the increase of Re, leading to a shift of the global stagnation point from the axis of symmetry.