Regimes identification of the viscous flow past an elliptic cylinder for Reynolds number up to 10000

In the present paper, the study of different regimes arising from the incompressible planar viscous flow past an elliptical cylinder is presented. In order to highlight the effect of the different parameters on the onset of the regimes, two different aspect ratios, 0.10 and 0.40, are considered and the angles of attack span from 0 to 90, while the Reynolds number is gradually increased from 100 to 10000. The analyses are focused on the lift force acting on the ellipse in order to identify the regime, with a consideration on the vorticity field patterns of the wake fields. The different regimes are investigated and the chaotic behaviour is established through different tools such as the Fourier spectra, phase maps and Poincaré sections. The investigation of the periodic regimes revealed several possible conditions in terms of lift time signal: monochromatic, non-monochromatic and sub-harmonic regimes. In addition, a quasi-periodic time behaviour with an underlying irregular amplitude modulation was also found among the test matrices performed. Increasing the Reynolds number the periodic regimes are lost, giving the place to chaotic behaviour. The numerical solutions are obtained through a vortex particle method called Diffused Vortex Hydrodynamics (DVH). Long time simulations have been carried out in order to guarantee the correct identification of the attained regime.