Change in wave-form and mean flow associated with wavelength variations in rotating Couette flow. Part 1

Abstract

When rotating Couette flow becomes unstable a periodic vortex structure is formed. For the wide-gap case, this flow is steady for a rather large range of the Taylor number above onset. In the region of finite amplitude instability the wave-numbers of the periodic structure are not unique. It is shown empirically that the non-uniqueness is not an end effect but a bonafide property of the flow and that the wave-form is a unique function of the wavelength. Data is presented to demonstrate the interval over which the wave-numbers can be varied when the parameters of the system are fixed. The large effect on the wave-form of small changes in the wavelength is also illustrated. These conclusions are based on extensive measurements of the azimuthal drift velocity for a particular mode of secondary flow.