TRANSITION AND CHAOS IN TWO-DIMENSIONAL FLOW PAST A SQUARE CYLINDER

This study numerically analyzes the unsteady wake of a long square cylinder. Velocity signals at selected locations in the near-wake and the instantaneous forces on the cylinder have been recorded from the numerical model at various Reynolds numbers. These form the basis of investigating the dynamic behavior of the flow system. Results revealed that flow past a square cylinder undergoes a sequence of transitions from a steady pattern up to a Reynolds number of 40 to a chaotic one around a Reynolds number of 600. The transition to chaos was manifested through a quasiperiodic route that included the frequency-locking phenomenon. The quasiperiodicity was seen to set in with two or more Hopf bifurcations. The transition to chaos in the wake of a bluff object was related to the three-dimensionality of the flow. In a two-dimensional simulation, this appeared in the form of new harmonics in the velocity traces. The quasiperiodic route to chaos has been established through different characterization tools, such as the spectra, autocorrelation function, time-delay reconstruction, and the Poincar section. Chaotic behavior was quantified through the calculation of Lyapunov exponent and fractal dimension.

Language

  • English

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Filing Info

  • Accession Number: 00794064
  • Record Type: Publication
  • Contract Numbers: DSWA01-97-C-0171, CMS-9800136, 99M6
  • Files: TRIS
  • Created Date: Jun 23 2000 12:00AM