The quiescent core of turbulent channel flow

Abstract

The identification of uniform momentum zones in wall-turbulence, introduced by Adrian, Meinhart & Tomkins (J. Fluid Mech., vol. 422, 2000, pp. 1-54) has been applied to turbulent channel flow, revealing a large 'core' region having high and uniform velocity magnitude. Examination of the core reveals that it is a region of relatively weak turbulence levels. For channel flow in the range Reτ = 1000-4000 it was found that the 'core' is identifiable by regions bounded by the continuous isocontour lines of the streamwise velocity at 0.95UCL (95 % of the centreline velocity). A detailed investigation into the properties of the core has revealed it has a large-scale oscillation which is predominant..