Adding the viscous term to the eigenmode equation for this phenomenon gives the Orr-Sommerfeld equation.  Rayleigh showed that in simple cases, a necessary condition for this phenomenon is that there be an inflection point in the velocity profile. Another common necessary co
Adding the viscous term to the eigenmode equation for this phenomenon gives the Orr-Sommerfeld equation.  Rayleigh showed that in simple cases, a necessary condition for this phenomenon is that there be an inflection point in the velocity profile. Another common necessary condition for this phenomenon is a value of less than one-fourth for the Richardson number. This phenomenon is responsible for the formation of high-altitude undulatus or "billow clouds" near jet streams, and it is suppressed by a parallel magnetic field if the AlfvÃ©n velocity exceeds the velocity change driving this instability. FTP, a vortex sheet at a velocity discontinuity is a simple case of what shearing instability named for British and German physicists?
Adding the viscous term to the eigenmode equation for this phenomenon gives the Orr-Sommerfeld equation.  
Kelvin-Helmholtz instability (accept shear instability or shearing instability before mention in the question)