Aerodynamic forcing characteristics of dry cable galloping at critical Reynolds numbers

(Received?; revised?; accepted?.- To be entered by editorial office) This article attempts to highlight characteristics of the aerodynamic forcing on a rigid circular cylinder experiencing dry galloping vibrations. Observations from a series of wind tunnel tests are studied comparatively with the literature on rain-wind cable vibrations and on flow past inclined lifting bodies such as missiles, for drawing similarities. Un-steadiness and spatial variation of the flow, both previously undermined, are significant during the large cylinder motions recorded. Thus, they are here suspected to play a role in triggering unstable behaviour. Instabilities were restricted to specific ranges of cable-wind angles and Reynolds numbers. The transitional features identified refute the view of simple bursting separation bubbles that rhythmically produce lift and suggest that there is a multitude of paths for energetically feeding dry galloping. Finally explanations are provided and a mechanism incorporating unstable features is proposed for future modelling. 1