Hydrodynamic Coefficients of the Transverse Force on a Circular Cylinder Oscillating Sinusoidally in Still Water

The alternating nature of vortex shedding and the induced transverse or lift forces are of significant importance in predicting structural responses, such as vortex-induced vibration and the associated fatigue. This paper reports a set of experimental results of the transverse force acting on a circular cylinder oscillating sinusoidally in still water. The measured transverse forces were analyzed using FFT(Fast Fourier Transform), and the coefficients of the mean and first four dominant frequency components, which are important for fatigue analysis, are examined for frequency parameter (β) ranging from 417 to 2083 and Keulegan-Carpenter number (KC) ranging from 4.8 to 28. The results showed that dominant transverse force component had a frequency double the oscillation frequency for most combinations of β and KC. We also found that for the transverse force coefficient it was possible to scale the force coefficient and the KC number to better correlate the scaled force coefficient with the scaled KC number. These scale factors reflect the influence of the frequency parameter on the measured transverse force coefficients.