Instability inside a rotating gas cylinder subject to axial periodic strain.

Yohann Duguet (1) , Julian F. Scott (1) , Lionel Le Penven (1)

1 LMFA - Laboratoire de Mecanique des Fluides et d'Acoustique

We study numerically the instability of a confined rotating gas flow subject to periodic strain along the axis of rotation, under the low Mach number approximation. An axisymmetric time-stepping spectral Galerkin-type code is used to investigate the viscous basic flow and its stability. Parametric resonance can lead to instability of this flow via the growth of inertial modes coupled by the oscillating strain. The marginal stability curve compares well with earlier experimental and (asymptotic) analytical results in the case of the axisymmetric inertial mode (1,1,0). The resulting flow is dominated by a time-oscillating toroidal vortex and differs very little from the theoretical mode. Two different nonlinear regimes are found, one with saturation to a constant modal amplitude, the other with weak periodic modulation. We also show evidence of the presence of an azimuthal circulation, apparently responsible for the observed modulation.

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Yohann Duguet, Julian F. Scott, Lionel Le Penven. Instability inside a rotating gas cylinder subject to axial periodic strain.. Physics of Fluids, 2005, 17, pp.114103. ⟨10.1063/1.2130746⟩. ⟨hal-00022327⟩