Absolute versus convective instability of spiral waves

Controlling the breakup of spiral waves in an excitable medium by applying time-delay feedback signals

– The spiral-wave breakup to turbulence in an excitable medium, starting from the spiral-wave center via Doppler instability, is controlled by modulating a local region around the spiral-wave center. The modulation signal is extracted from the controlled region with a certain time delay. By injecting a feedback signal with very low intensity into a very small space area, we can successfully sta...

The stability of the boundary layer on a sphere rotating in a uniform axial flow

We consider the local convective and absolute instabilities of the boundary layer on a rotating sphere located in a uniform axial flow, extending our previous work, which considered still outer fluid. Axial flow is seen to stabilise the convective instabilities, and our predicted onset of the spiral vortices is in good agreement with existing experimental data. The vortex angle is found to incr...

Convective and absolute electrokinetic instability with conductivity gradients

Electrokinetic flow instabilities occur under high electric fields in the presence of electrical conductivity gradients. Such instabilities are a key factor limiting the robust performance of complex electrokinetic bio-analytical systems, but can also be exploited for rapid mixing and flow control for microscale devices. This paper reports a representative flow instability phenomenon studied us...

Convective and absolute Eckhaus instability leading to modulated waves in a finite box.

We report an experimental study of the secondary modulational instability of a one-dimensional nonlinear traveling wave in a long bounded channel. Two qualitatively different instability regimes involving fronts of spatiotemporal defects are linked to the convective and absolute nature of the instability. Both transitions appear to be subcritical. The spatiotemporal defects control the global m...

Criteria for convective versus absolute string instability in car-following models