Effect of damping on interference-induced oscillations of two identical circular cylinders

Abstract Considerable information has been accumulated in the last two decades on wind loads exerted on two parallel circular cylinders. However, the threshold of aerodynamic instability caused by flow interference has not yet been established. This paper describes experiments where damping was varied systematically using electromagnets. The Scruton number (logarithmic decrement times mass ratio) was varied from 10 to 300 and the critical damping necessary to suppress the oscillation of two elastically mounted circular cylinders was determined. All three interference regions are covered: proximity, wake and combinations of these.