AZIMUTHAL AND STREAMWISE DISTURBANCES IN A FLUID LAYER FLOWING DOWN AROTATING CYLINDER

In this paper an extensive investigation is done of the linear stabili ty of a film falling down a vertical rotating cylinder. Two cases are considered: flow in the outside and flow in the inside of the cylinder . To this end, a system of differential equations which describe the i nstability is solved numerically with the Runge-Kutta fourth and sixth order methods. We show that in different circumstances the azimuthal disturbances become the most unstable when the rotation is taken into account. Moreover, a splitting of the azimuthal modes appears due to t he Coriolis force. In the case of flow in the inside there is a thresh old in the centrifugal force above which the-flow is linearly stable. Besides, new results for the nonrotating case are also obtained. (C) 1 997 American Institute of Physics.