Stability of a cylindrical shell in a stratified flow

Analysis of the Kelvin stability of a horizontal plane flow of two fluid layers of different densities and one moving relative to the other is extended to the case of longitudinal coaxial flow of a two-layered fluid within a circular cylindrical shell. It is shown that the loss of stability of the whole system sets in for low velocities of the layer motion, one relative to the other. A comparison is made with classical flutter for which the flow is not stratified.