Modulation effects along stability border in Taylor–Couette flow.

The stability of time modulated Taylor-Couette flow with co- and counter-rotating cylinders and modulated inner cylinder velocity is investigated. The mean velocities of the inner and outer cylinders are chosen to be in constant relative distance to the stability border of nonmodulated Taylor-Couette flow and the inner cylinder velocity is periodically modulated. The critical modulation amplitude, which leads to linear instability of the modulated laminar flow, is calculated with numerically integrated Floquet theory, as well as with perturbation theory. The critical modulation amplitude as a function of the outer cylinder Reynolds number has a richstructure for counter-rotating cylinders, which is open to experimental test. The critical modulation amplitude decreases monotonically with increasing rotation frequency for corotating cylinders. [ABSTRACT FROM AUTHOR]