Rotating Polygons on a Fluid Surface

Tomas Bohr, Thomas Jansson, Martin Haspang, Kaare Jensen, Pascal Herson

Research output: Contribution to conferenceConference abstract for conferenceResearchpeer-review

Abstract

The free surface of a rotating fluid will, due to the centrifugal force, be pressed radially outward. If the fluid rotates as a rigid body in a cylindrical container the surface will assume a parabolic shape. If, however, the flow is driven by rotating the bottom plate, the axial symmetry can break spontaneously and the surface can take the shape of a rigidly rotating polygon. With water we have observed polygons with up to 6 corners. The rotation speed of the polygons does not coincide with that of the plate, but it is often mode-locked, such that the polygon rotates by one corner for each complete rotation of the plate. It has been known for many years that such flows are prone to symmetry breaking. The creation of rotating waves inside the container was observed for Reynolds numbers up to around 3000, where the free surface remains essentially flat (see J. M. Lopez and F. Marques and A. H. Hirsa and R. Miraghaie, ”Symmetry breaking in free-surface cylinder flows”, J. Fluid Mech., 502, 99 (2004)). The polygons occur at much larger Reynolds numbers, for water around 500.000. Correspondingly, the dependence on viscosity is rather small.
Original languageEnglish
Publication date2005
Publication statusPublished - 2005
Event58th Annual Meeting of the APS Division of Fluid Dynamics - Hilton Chicago Hotel, Chicago, United States
Duration: 20 Nov 200522 Nov 2005
Conference number: 58

Conference

Conference58th Annual Meeting of the APS Division of Fluid Dynamics
Number58
LocationHilton Chicago Hotel
CountryUnited States
CityChicago
Period20/11/200522/11/2005

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