Flow patterns and organization within a turbulent spot

R. Sankaran*, R. A. Antonia, D. K. Bisset, M. Sokolov

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Recent investigations of turbulent spots within laminar flat plate boundary layers have identified coherent structures which make up the spots. The present paper focuses on the topology of the flow associated with these structures. An array of X probes aligned in the direction normal to the wall has been used to obtain u (streamwise) and v (normal to the wall) velocity fluctuations at three streamwise locations both in and outside the plane of symmetry. The "most probable spot" (MPS), which contains the statistically most probable number of structures, is presented and discussed in the context of instantaneous realizations, overall ensemble averages with respect to the spot leading edge, and averages conditioned on individual structures within the spot. Sectional streamlines for single realizations and for a composite of averages conditioned on the structures show a succession of saddles and foci similar to the topology of a turbulent boundary layer. Percentage contributions from individual structures to the Reynolds stresses are similar to those previously reported for the large-scale motion in a turbulent boundary layer, except near the trailing edge of the spot. The height and spacing of structures, and the distributions of spanwise vorticity and strain rate, all appear to be more regular away from the plane of symmetry.

Original languageEnglish
Pages (from-to)1560-1571
Number of pages12
JournalPhysics of fluids. A, Fluid dynamics
Issue number6
StatePublished - 1991


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