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Third Symposium on Turbulence and Shear Flow Phenomena
June, 25-27, 2003, International Center, Sendai, Japan

DOI: 10.1615/TSFP3

SPATIO-TEMPORAL EVOLUTION OF COHERENT VORTICES IN WALL TURBULENCE WITH STREAMLINE CURVATURE

pages 139-144
DOI: 10.1615/TSFP3.240
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RÉSUMÉ

The effect of wall curvature on the turbulent structure in curved channel flow is investigated by means of direct numerical simulation (DNS). Four different radii of curvature, δ/Rc = O.013, 0.05, 0.1 and 0.2, are studied. The DNS results show: 1) reduction of turbulence intensities on the convex wall, and 2) increase of radial turbulence intensity in the central region of channel with the increase of curvature. It is revealed that such turbulence modulation is attributed to the extra production of the Reynolds stress caused by the centrifugal force. Moreover, a spatio-temporal LSE (Linear Stochastic estimation) is applied in order to extract the development of turbulence- producing eddies affected by centrifugal force. It is clarified that the development of turbulence-producing motion is associated with the large-scale strong roll-cell working against the centrifugal stabilizing effect on the convex side, whereas those vortices are not observed on the concave side. In addition, strong outward and inward motions induced by the roll cell in the channel central region appear prior to the development of second and fourth quadrant motions, respectively.

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