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POD Spectrum of the Wake behind a Circular Cylinder

The wake dynamics behind a long circular cylinder in cross-flow was studied using the POD method. The temporal parts of POD modes, Chronoses, are subjected to frequency analysis. Five groups of modes are distinguished according to the frequency contents. The low order high energy modes contain the vortex shedding frequency or its harmonics up to 3rd order plus Kolmogorov spectrum. The higher order modes are characterized by combination of Kolmogorov spectrum with the white noise spectrum, its importance grows with the mode order. The very high order modes are characterised by the white noise spectrum only.