Turbulent flow and the effects of curvature

Multi-sensor measurements have been made in an axisymmetric Couette flow and in a curved mixing-layer formed by detachment of a thick boundary layer from the trailing edge of a plane surface. For the Couette flow, large eddies highly elongated in the flow direction are found for Reynolds numbers in the range 10,000 to 100,000, but they occur as equally spaced, toroidal eddies only for Reynolds numbers less than 40,000. At higher Reynolds numbers, the large eddy structure takes the form of helical eddies interspersed with occasional toroidal eddies and patches of unorganized flow. The curved mixing layer is a curiosity, being initially a mixture of a growing layer with periodic fluctuations of velocity whose phase changes with displacement across the width of the layer.