title: Direct velocity measurement of a turbulent shear flow in a planar Couette cell.
abstract: In a plane Couette cell a thin fluid layer consisting of water is sheared between the sides of a transparent band at Reynolds numbers ranging from 300 to 1400. The length of the cell's flow channel is large compared to the film separation. To extract the flow velocity in the experiments, a correlation image velocimetry method is used on pictures recorded with a high-speed camera. The flow is recorded at a resolution that allows us to analyze flow patterns similar in size to the film separation. The fluid flow is then studied by calculating flow velocity autocorrelation functions. The turbulent patterns that arise on this scale above a critical Reynolds number of Re=360 display characteristic patterns that are proven by use of the calculated velocity autocorrelation functions. The patterns are metastable and reappear at different positions and times throughout the experiments. Typically these patterns are turbulent rolls which are elongated in the stream direction, which is the direction in which the band is moving. Although the flow states are metastable they possess similarities to the steady Taylor vortices known to appear in circular Taylor Couette cells.
authors.affiliation: Department of Physics, University of Oslo, P. O. Box 1048, 0316 Oslo, Norway.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Niebling
authors.affiliation: Department of Physics, University of Oslo, P. O. Box 1048, 0316 Oslo, Norway.
authors.forename: Ken Tore
authors.initials: KT
authors.lastname: Tallakstad
authors.affiliation: Institut de Physique du Globe de Strasbourg, EOST/Université de Strasbourg, CNRS, 5 rue Descartes, F-67000 Strasbourg, France.
authors.forename: Renaud
authors.initials: R
authors.lastname: Toussaint
authors.affiliation: Department of Physics, University of Oslo, P. O. Box 1048, 0316 Oslo, Norway.
authors.forename: Knut Jørgen
authors.initials: KJ
authors.lastname: Måløy