Article contents
Mode competition in modulated Taylor–Couette flow
Published online by Cambridge University Press: 25 April 2008
Abstract
The effects of harmonically oscillating the inner cylinder about a zero mean rotation in a Taylor–Couette flow are investigated experimentally and numerically. The resulting time-modulated circular Couette flow possesses a Z2 spatio-temporal symmetry which gives rise to two distinct modulated Taylor vortex flows. These flows are initiated at synchronous bifurcations, have the same spatial symmetries, but are characterized by different spatio-temporal symmetries and axial wavenumber. Mode competition between these two states has been investigated in the region where they bifurcate simultaneously. In the idealized numerical model, the two flows have been found to coexist and be stable in a narrow region of parameter space. However, in the physical experiment, neither state has been observed in the coexistence region. Instead, we observe noise-sustained flows with irregular time-dependent axial wavenumber. Movies are available with the online version of the paper.
- Type
- Papers
- Information
- Copyright
- Copyright © Cambridge University Press 2008
References
REFERENCES
Avila et al. supplementary movies
Movie 1 Numerical simulation of type B (non-reversing) Taylor vortex flow between two concentric cylinders. The outer cylinder (right boundary) is held stationary whereas the inner cylinder (left boundary) rotates harmonically about a zero-mean with Re(t)=Rea sin(ωt). Centrifugal instability is triggered every half-period and results in synchronous secondary Taylor vortex flows. In the high-frequency regime shown in this movie, this instability is manifested by angular momentum jets erupting from the inner cylinder at a fixed axial location. Angular momentum (ωθ) and azimuthal vorticity (rvθ) are shown in a meridional cross-section at ω=6.1 and Rea=240. Red (blue) corresponds to positive (negative) values. The wavenumber of the axially periodic pattern is kB=3.4. The movie corresponds to figure 8 in the paper.
Avila et al. supplementary movies
Movie 2 Numerical simulation of type A (reversing) Taylor vortex flow at ω=1 and Rea=240 with wavenumber kA=3.0. In the low-frequency regime shown in this movie, the angular momentum jets shift their locations by half the wavelength of the pattern when the inner cylinder reverses its direction of rotation. Angular momentum and azimuthal vorticity are shown in a meridional cross-section. Red (blue) corresponds to positive (negative) values. The movie corresponds to figure 10 in the paper.
- 20
- Cited by