The effect of damping and mass ratio on the stability of a tube bank

Abstract Experiments have been conducted in a wind tunnel on a parallel triangular tube array with a pitch ratio of 1·375. The aerodynamic component of damping was determined as a function of flow velocity. This damping was found to increase linearly with flow to about 50% of the stability threshold and then to decrease. Additionally, six different sets of tubes were tested to examine the effect of mass ratio on fluid-elastic stability. The results were compared with similar experiments in which damping alone was varied. It is seen that damping and mass ratio do not appear to be linearly dependent parameters which is contrary to the assumption used commonly in the stability analysis of tube banks. More importantly, however, the stability threshold is substantially less dependent on both damping and mass ratio than indicated by conventional theory.