PULSED FLOW BETWEEN CONCENTRIC ROTATING CYLINDERS

A theoretical and experimental investigation of the stability of the m odulated Bow in a Taylor-Couette geometry with both cylinders subject to in-phase or out-of-phase modulated rotation with the same amplitude and frequency is presented. The experimental observations for in-phas e modulations show that the Bow is stabilized at high and low modulati on frequencies while some destabilization at intermediate frequencies is revealed, in agreement with the theoretical results from a linear s tability analysis carried out in the narrow gap limit. The observation s for out-of-phase modulations show stabilization at high frequencies while for low modulation frequencies the stability curve reaches an as ymptotic value somewhat higher than the one corresponding to the onset of instability for steady Couette Bow between counter-rotating cylind ers. The numerical results obtained in this case compare well with the experimental findings at high and moderate frequencies, but show some disagreement at low frequencies.