Stability of Rotating Couette Flow. I. Asymmetric Waveforms

Experiments are described which show that the waveform at onset of instability in rotating Couette flow may be asymmetric about the rotational axis. Thus, the prediction of Krueger, Gross, and DiPrima is verified. The waveforms have been observed using various cylinders with gap ratios ranging from 0.20 to 0.96. The data covers the complete range where simple asymmetric modes occur. A complicated transient motion is described which leads to the spiral waveforms observed at onset. All predictions of Krueger et al. are in accord with experiment and previous experimental work can be reconciled with both the theory and the present observations. A waveform which is subharmonic in the axial direction is also studied.