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Transport Phenomena in Thermal Engineering. Volume 2

ISBN:
1-56700-015-0 (Print)

THE EFFECTS OF CORIOLIS AND CENTRIFUGAL FORCES ON TRANSITION TO TURBULENCE IN A ROTATING CURVED RECTANGULAR CHANNEL

K. C. Cheng
Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, CANADA

Liqiu Wang
Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, CANADA

Abstract

Flow visualization results obtained by smoke injection method are presented to study the effects of Coriolis and centrifugal forces on secondary flow patterns revealing transition to turbulence in a rotating curved rectangular channel (aspect ratio = 1) for Dean numbers K1 = 150, 250 and 450 and rotating speed n in the range n = 0 − 402 rpm with both positive and negative rotations. For negative rotation, the Coriolis vortices in the form of longitudinal vortex rolls are formed near the inner wall at lower rotating speeds and destruction of the vortices occurs at higher rotating speeds leading to turbulent flow. For positive rotation the Coriolis forces have destabilizing effects on Dean vortices and the transition to turbulent flow occurs at lower rotating speeds than the case with negative rotation. The photographic results presented provide considerable insight into the transition phenomena involving Coriolis and centrifugal forces and complement measurements and theoretical studies.