Temporal stability of boundary-free shear flows: The effects of diffusion

The stability of boundary-free shear flow is studied for the case of variab le viscosity due to binary diffusion across the shear layer. This leads to the main difficulty of this investigation, the direct coupling of the momen tum and species equations in both the base state calculations as well as th e stability analysis. Linear stability analysis is used to examine the effect of a nonuniform con centration profile on the stability of the flow. it is found that for the f low to be stable for all disturbance wave numbers the Reynolds number has t o be zero. This is in agreement with constant viscosity free shear flow sta bility theory. Increasing the magnitude of concentration gradient (increasi ng the Schmidt number) destabilizes the flow.