Added Stiffness Relating to Small Motions of Two Concentric Cylinders Submitted to Axial Annular Incompressible Flow

Abstract
Axial incompressible, viscous flow is considered in an annular gap between two rigid cylinders. If the cylinders are displaced from their concentric positions in a certain manner, the displacement will cause reaction forces exerted by the fluid pressure. In this investigation the pressure fluctuations caused by the displacement of the structures are approximated by analytical means. Pressure fluctuations in phase with acceleration and velocity of the structure are not calculated here. Stationary flow is considered, because structural displacements are assumed to be small.