Wind Tunnel Tests on Two Cylinders to Measure Subspan Oscillation Aerodynamic Forces

The wind tunnel campaign was performed on two circular cylinders to investigate subspan oscillation, a typical phenomenon that affects high-voltage and ultra-high-voltage overhead transmission lines. In particular, aerodynamic forces were measured in static and in dynamic conditions. Dynamic conditions were realized by moving the cylinders along quasielliptical orbits as when subspan oscillation occurs. Tests were performed by changing the relative position between the two cylinders, the frequency and the amplitude of the motion, and the wind velocity, that is, the Reynolds number. Both smooth and rough cylinders were tested. The effects of all these parameters in the evaluation of the energy introduced or dissipated by the system have been highlighted, with special care for the Reynolds number effects.