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Laboratory experiments on rotating turbulence have been conducted to explore the formation of columnar vortices in a forced steady-state environment. Forcing was achieved by means of co-rotating impellers situated at the top and bottom surfaces of a large cylindrical tank of height 2 m and diameter 2 m. As the impellers rotated the fluid, the turbulence generated, characterized by the root mean squared (rms) velocity |u|, was controlled using symmetrically located baffles on the inner walls of the tank. By varying the rms velocity |u| and bulk rotation rate Omega, the flow was investigated over a range of in-plane Rossby numbers, |u|/2*Omega*l. 2D Particle image velocimetry (PIV) was carried out for a plane normal to the axis of rotation at the center of the tank, and was utilized to compute velocity fields and streamlines which revealed the emergence of columnar eddies, as is often seen in decaying experiments on rotating turbulence. PIV results were used to deduce the parameters affecting the structure, frequency of occurrence and life cycle of these columns. The tendency of columns to be predominantly cyclonic and the effect of columns on bulk rotation rate were also analyzed.
Author(s):
Lian Gan
University of Cambridge
United Kingdom
Yasir B. Baqui
University of Cambridge
United Kingdom
Peter A. Davidson
University of Cambridge
United Kingdom
Per-Aage Krogstad
Norwegian University of Science and Technology
Norway
James R. Dawson
University of Cambridge
United Kingdom