Large-scale investigation of a turbulent bifurcation in the swirling Von Karman flow

Abstract : We investigate the large-scale organization of the swirling Von Karman flow using proper orthogonal decomposition. Results from two decomposition domains are confronted with each other: one is limited to a section of the cylinder (half the meridian plane), while the other consists of the full plane. Previous studies have established that the flow can be characterized by metastable states, which break the Rπ symmetry (rotation with respect to a radial axis in the mid-height plane). We show that contributions to the flow symmetry-breaking come in a substantial part from large-scale POD modes with even azimuthal wavenumbers, thereby establishing a connection between the Eckhaus-like instability observed by Herbert et al (2014 Phys. Fluids 28 0151038) and the Rπ symmetry-breaking reported by Cortet et al (2010 Phys. Rev. Lett. 105 214501). At the edges of the range where the flow is most susceptible to symmetry-breaking, the large-scale organization of the flow is very similar and most of the flow dissymmetry is dominated by a single large- scale component. A reconstruction of the dominant fluctuation is attempted at Re=43 000 and Re=128 000. In contrast, the global angular momentum is largely decorrelated from its large-scale contribution at Re=84 000, in agreement with Cortet et alʼs identification of a phase transition around this Reynolds number.
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Submitted on : Monday, November 26, 2018 - 5:10:41 PM
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Bérengère Podvin, Bérengère Dubrulle. Large-scale investigation of a turbulent bifurcation in the swirling Von Karman flow. Fluid Dynamics Research, IOP Publishing, 2018, 50 (6), ⟨10.1088/1873-7005/aae166⟩. ⟨cea-01935496⟩

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