On the Flutter of a Smooth Circular Cylinder in a Wake

Abstract

SummaryThe stability of a smooth circular cylinder, free to translate horizontally and vertically against linear springs in the wake from an identical neighbouring cylinder, is studied using quasi-static aerodynamic derivatives and simple flutter theory. It is found that at spacing values between ten and twenty cylinder diameters (typical of the spacings employed on “bundled” overhead transmission lines) classical flutter of the leeward cylinder can occur in a certain critical range of wind speeds at certain orientations of this cylinder in the wake. However, the occurrence of flutter appears to be conditional on a positive difference of natural frequency between vertical and horizontal motions of the leeward cylinder in still air.Classical static instability (divergence) of the leeward cylinder is also shown to be possible over the entire “incidence” range in the wake, but this occurs in a much higher wind speed range than that associated with flutter.