Characteristics of amplitude vacillation in a differentially heated rotating fluid annulus

Abstract

Experimental results are presented on the characteristics and occurrence of amplitude vacillation observed in the regular wave regime of a differentially heated rotating fluid annulus. The amplitude vacillation appears as the periodic oscillation of the amplitude and frequency of the dominant wave component and its harmonics and occurs, in general, adjacent to a transition to the next lowest wavenumber. The frequency spectra of the amplitude vacillations are characterized by the presence of two distinct frequencies, one from the vacillation and one from the drift of the wave; in general the amplitude vacillations observed can be said to be doubly periodic. The wave interference mechanism of amplitude vacillation is examined but no evidence was found which could be unambiguously interpreted in its favour.