Effects of background rotation on a towed-sphere wake in a stably-stratified fluid

Spedding, G.R. and Fincham, A.M. (1999) Effects of background rotation on a towed-sphere wake in a stably-stratified fluid. Il nuovo cimento C, 22 C (6). pp. 875-884. ISSN 1826-9885

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The wake of a towed sphere in a stable background density gradient can be considered a convenient model problem for studying the emergence and longevity of the coherent patches of alternate-signed vertical vorticity that comprise the late wake. In practical applications it is likely that the lifetime is such that rotation effects should also be considered, and strong rotation can also be used to deliberately disturb the inferred three-dimensional wake structure. Competing effects of stratification and rotation can be measured by the ratio of rotation to buoyancy timescales, fON, which varies from 0.05 to 0.22 in experiments conducted on the 14 m diameter rotating table at Coriolis. Wake anticyclones, with sense of rotation opposite to the background rotation, were spread out over a larger area, and were less strongly peaked than their cyclonic counterparts, with the magnitude of the asymmetry depending on fON. Deformation of anticyclones into highly elliptical shapes coincided with a broader range of wake vortex interactions than in the non-rotating case. At much longer times (hundreds of buoyancy periods, 5-10 rotation times), a recircularisation of elliptical anticyclones can occur. The observed asymmetries are consistent with existing data on homogeneous wake flows with rotation.

Item Type: Article
Additional Information: Paper presented at the International Workshop on “Vortex Dynamics in Geophysical Flows”, Castro Marina (LE), Italy, 22-26 June 1998.
Uncontrolled Keywords: Coriolis effects; Turbulence and diffusion; Stratified flows; Wakes; Conference proceedings
Subjects: 500 Scienze naturali e Matematica > 550 Scienze della Terra
Depositing User: Marina Spanti
Date Deposited: 11 Oct 2019 15:03
Last Modified: 11 Oct 2019 15:03
URI: http://eprints.bice.rm.cnr.it/id/eprint/13682

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