Fluid-elastic instabilities caused by flow in an annulus

An analysis is presented of the way in which fluid flow in a narrow annulus between concentric cylinders can lead to fluid-elastic instabilities of the cylinders in one of their modes of vibration. It is shown that fluid-structure interactions give rise to aerodynamic damping which varies with the fluid velocity down the annulus; this damping is also controlled by the boundary conditions assumed for the fluid both upstream and downstream, an important consideration often previously disregarded in analyses of this sort. The work also demonstrates how the added mass associated with the fluid in the annulus is affected by a steady flow. Some experimental results are described. (author)