An implicit method for coupled flow-body dynamics

  • Authors:
  • Silas Alben

  • Affiliations:
  • School of Mathematics, Georgia Institute of Technology, 686 Cherry Street, Atlanta, GA 30332-0160, United States

  • Venue:
  • Journal of Computational Physics
  • Year:
  • 2008

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Abstract

We propose an efficient method for computing coupled flow-body dynamics. The time-stepping is implicit, and uses an iterative method (preconditioned GMRES) to solve the flow-body equations. The preconditioner solves a decoupled version of the equations which involves only the inversion of banded matrices, and requires a small number of iterations per time step. We use the method to probe the instability to horizontal motions of an elliptical body with simple vertical motions: flapping and rising. In both cases a linear instability to horizontal motion sets in above a critical Reynolds number, leading to a stable oscillatory state. The pressure forces play a destabilizing role against the stabilizing viscous forces, with oscillatory time scales set by either external flapping or the intrinsic flow-body coupling. The latter lowers the instability threshold in Reynolds number.