Rotational instability of viscosity stratified flow*

Instability of stratified multi-phase flow has drawn the attention in a rotating platform because of its potential role in micro-mixing for medical instruments.Centrifugal actuation can play an important role in driving the flow and Coriolis force can make enhance the mixing in a short span by destabilizing the flow. Here, we focus on the impact of the Coriolis force on viscosity-stratified flow with a miscible layer. Modal stability analysis is used to estimate the critical parameters, namely Rotation number, Reynolds number and wave numbers, which are responsible to vary the instability mechanism for different viscosity contrast. The study explores competing influence of rotational forces against the viscous forces. Correspondingly, rotational direction shows a significant effect on the spatio-temporal instability mechanism. Usually, miscible viscosity stratified flow with streamwise disturbance becomes more unstable for thinner mixed layer. On the contrary, our numerical computation confirms complete opposite scenario for Coriolis based instability of a miscible system with spanwise disturbances. The primary mechanism for the same can be inspected through the base flow of the system. Comparison between two and three dimensional instability is done.