Coincidence of turbulent-nonturbulent interface and hot-cold interface in a plane turbulent wake

A plane turbulent wake generated by a flat plate is subjected to a uniform distortion. It is observed that nearly two-dimensional, quasi-periodic coherent structures dominate the distorted wake. Rapid distortion theory, applied to a kinematic vortex model of the coherent structures in the undistorted far wake, predicts many of the effects revealed by a hot-wire anemometry/pattern-recognition analysis of these structures. Specifically, rapid distortion theory predicts reasonably well the observed changes in the ensemble-averaged velocity patterns and the disproportionate amplification of the large-scale coherent structures relative to the smaller-scale ‘isotropic’ eddies. These results are consistent with the view that self-preservation of the distorted wake is not possible because of the selective amplification of the coherent structures, which control the development of the wake. As well, the entrainment rate in the distorted wake increases at a rate greater than that predicted by the self-preservation theory.

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Three-dimensionality of organized structures in a plane turbulent wake

Journal of Fluid Mechanics ◽

10.1017/s0022112089002338 ◽

1989 ◽

Vol 206 ◽

pp. 375-404 ◽

Cited By ~ 84

Author(s):

Michio Hayakawa ◽

Fazle Hussain

Keyword(s):

Cross Sections ◽

Coherent Structures ◽

Near Field ◽

Spatial Coherence ◽

Three Dimensional ◽

Quantitative Measure ◽

Turbulent Wake ◽

Topological Features ◽

Plane Wake ◽

Plane Turbulent Wake

This paper describes a quantitative study of the three-dimensional nature of organized motions in a turbulent plane wake. Coherent structures are detected from the instantaneous, spatially phase-correlated vorticity field using certain criteria based on size, strength and geometry of vortical structures. With several combinations of X-wire rakes, vorticity distributions in the spanwise and transverse planes are measured in the intermediate region (10d [les ] x [les ] 40d) of the plane turbulent wake of a circular cylinder at a Reynolds number of 13000 based on the cylinder diameter d. Spatial correlations of smoothed vorticity signals as well as phase-aligned ensemble-averaged vorticity maps over structure cross-sections yield a quantitative measure of the spatial coherence and geometry of organized structures in the fully turbulent field. The data demonstrate that the organized structures in the nominally two-dimensional wake exhibit significant three-dimensionality even in the near field. Using instantaneous velocity and vorticity maps as well as correlations of vorticity distributions in different planes, some topological features of the dominant coherent structures in a plane wake are inferred.

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Temperature fluctuations in the plane turbulent wake

The Physics of Fluids ◽

10.1063/1.1694651 ◽

1974 ◽

Vol 17 (11) ◽

pp. 1956 ◽

Cited By ~ 70

Author(s):

John C. LaRue

Keyword(s):

Temperature Fluctuations ◽

Turbulent Wake ◽

Plane Turbulent Wake

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Anisotropy of the temperature dissipation in a turbulent wake

Journal of Fluid Mechanics ◽

10.1017/s0022112086002343 ◽

1986 ◽

Vol 163 ◽

pp. 393-403 ◽

Cited By ~ 33

Author(s):

R. A. Antonia ◽

L. W. B. Browne

Keyword(s):

Transport Equation ◽

Shear Flows ◽

Turbulent Wake ◽

Turbulent Shear ◽

Temperature Variance ◽

Approximate Equality ◽

Turbulent Shear Flows ◽

Measured Ratio ◽

Plane Turbulent Wake ◽

Isotropic Dissipation

Measurements by Freymuth & Uberoi (1971) of the terms in the transport equation for the temperature variance in a plane turbulent wake indicated approximate equality for the three components of the temperature dissipation, thus indicating isotropy for that quantity. This result was in sufficient disagreement with the results obtained in several other turbulent shear flows to warrant further measurements of the temperature dissipation in the wake. The present measurements indicate that the dissipation is larger than the isotropic value by about 50 % near the wake centreline and nearly 100 % near the region of maximum production. The magnitude of this ratio is similar to that obtained in other turbulent shear flows. The present measured ratio of total dissipation to isotropic dissipation leads to a satisfactory closure of the temperature variance budget for our experiments and also for the plane-wake measurements of Fabris (1974). It is concluded that the temperature dissipation is not isotropic.

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