  Instability mechanism based on Coriolis force, on a rapidly rotating portable
device handling shear thinning fluids such as blood, is of utmost importance
for eventual detection of diseases by mixing with the suitable reagents.
Motivated by this proposition, the present study renders a modal stability
analysis of shear thinning fluids in a rotating microchannel modelled by the
Carreau rheological law. When a microchannel is engraved a rotating compact
disc (CD) based device, the centrifugal force acts as the driving force that
actuates the flow and the Coriolis force enhances the mixing process in
significantly short span by destabilizing the flow. An OrrSommerfeld-Squire
analysis is performed to explore the role of these forces on the linear
stability of rotating shear-thinning flow. Reported results on shear thinning
flow with streamwise disturbances indicate that the critical Reynolds number
for the flow transition with viscosity perturbation is nearly half of that of
the critical value for the same without viscosity perturbation. In sharp
contrast, the present analysis considering spanwise disturbances reveals that
the critical Reynolds numbers with and without viscosity perturbation remain
virtually unaltered under rotational effects. However, the viscosity variation
has no significant influence on the Coriolis force-based instability. Numerical
results confirm that a momentous destabilization is possible by aid of the
Coriolis force via generating secondary flow inside the channel. Interestingly,
the roll cells corresponding to the instabilities at lower time constants
exhibit the existence of two distinct vortices, and the centre of the stronger
one is essentially settled towards the unstable stratified region. Moreover,
for a higher value of the time constant, only one vortex occupies the entire
channel.
