284 research outputs found
Transient Turbulence in Taylor-Couette Flow
Recent studies have brought into question the view that at sufficiently high
Reynolds number turbulence is an asymptotic state. We present the first direct
observation of the decay of turbulent states in Taylor-Couette flow with
lifetimes spanning five orders of magnitude. We also show that there is a
regime where Taylor-Couette flow shares many of the decay characteristics
observed in other shear flows, including Poisson statistics and the coexistence
of laminar and turbulent patches. Our data suggest that characteristic decay
times increase super-exponentially with increasing Reynolds number but remain
bounded in agreement with the most recent data from pipe flow and with a recent
theoretical model. This suggests that, contrary to the prevailing view,
turbulence in linearly stable shear flows may be generically transient.Comment: 4 pages, 4 figures v2: Addressed referee comments for PRE. Made some
cosmetic changes. Added inset to Fig.
Homology and symmetry breaking in Rayleigh-Benard convection: Experiments and simulations
Algebraic topology (homology) is used to analyze the weakly turbulent state
of spiral defect chaos in both laboratory experiments and numerical simulations
of Rayleigh-Benard convection.The analysis reveals topological asymmetries that
arise when non-Boussinesq effects are present.Comment: 21 pages with 6 figure
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