On the nonlinear interfacial instability of rotating core-annular flow (Q1313905)

This paper investigates the stability of the flow of two immiscible fluids of different viscosities and densities, flowing in a circular pipe in a concentric arrangement. The cylinder is allowed to rotate, and a constant axial pressure gradient is prescribed. The stability of the basic flow is considered by linear and weakly nonlinear methods. A detailed analysis is given of the case where the thickness of the outer ``ring'' of fluid is very small, by solving the equations for the velocity and pressure fields in the core and film regions, and then by deriving a nonlinear parabolic integro-differential evolution equation for disturbances to the interface between the two fluids. This evolution equation is solved numerically, and extensive results are provided.