title: Oscillating large-scale circulation in turbulent Rayleigh-Bénard convection.
abstract: We report on the dynamics and structure of the turbulent velocity field in a high-Rayleigh-number (Ra = 5.9 x 10(8))thermal convection cell with an aspect ratio of 4. Spectral density functions (measured with laser Doppler velocimetry) indicated the existence of a large-scale periodic component. The long-time mean flow field (measured with particle image velocimetry) revealed that the large-scale circulation in the aspect-ratio-4 cell consists of two corotating rolls. The periodicity in the flow could be traced back to the alternating growth and decay of these rolls.
authors.affiliation: Department of Multi-Scale Physics, Delft University of Technology, The Netherlands. j.verdoold@ws.tn.tudelft.nl
authors.forename: Jos
authors.initials: J
authors.lastname: Verdoold
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Tummers
authors.forename: Kemo
authors.initials: K
authors.lastname: Hanjalić