The galloping instability of ice coated poles

Abstract A wind tunnel investigation of the lift and drag of cylinders over Reynolds Numbers (Based on diameter) from 50,000 to 500,000 for ice thicknesses from 1.5 to 25% of cylinder diameter has been performed. The study revealed that for typical 120° circumferential coverages there is a critical ice thickness (3–6% of the diameter) that can result in a negative Den Hartog coefficient of −10 with a total negative change in lift coefficient of about 1.0 near zero angle of attack. The consequences of this finding in terms of the design of poles is discussed and a few comparisons between predicted and measured amplitudes made.