National Research Council of Canada. NRC Institute for Aerospace Research
5th European and African Conference on Wind Engineering, July 19-23, 2009, Florence, Italy
cable aerodynamics; inclined circular cylinder; critical Reynolds number
The current paper considers large vibrations of circular cylinders, inclined and yawed to the flow. The case of a nominally perfect cylinder prone to galloping-like instabilities, when subjected to some critical flow conditions, is seemingly a paradox since symmetry and aerodynamic galloping are contradictory. Symmetry-breaking parameters in the flow geometry were suspected to be associated with triggering mechanisms of such vibration phenomena. A series of wind tunnel tests was performed on a full-scale inclined spring-supported cable model for a range of conditions in order to assess this idea further. We herein describe the experimental setup, present deduced results and attempt to provide explanations for the observed behaviour in the light of established knowledge in the field. We use instantaneously recorded pressure measurements to map flow transitions, recover energetic structures around the cylinder body and examine force correlations. Incidents of large response with negative aerodynamic damping are examined considering axial flow, spanwise vortex shedding and Reynolds number influences.
Firenze University Press
Proceedings of 5th European and African Conference on Wind Engineering.