Streamwise Oscillations of a Cylinder in Steady Current: Simulation of Long Wave Interaction with a Stationary Cylinder : Part A

Streamwise oscillations of a cylinder in steady current: simulation of long wave interaction with a stationary cylinder. For exactly the same oscillation and flow conditions, two distinct phase-locked modes are admissible. The sequence of images shown in the left column corresponds to a signature of the transverse-force coefficient C_y having a pronounced negative peak, then a region of nearly zero C_y, followed by a pronounced positive peak. The peak at N = 10 corresponds to an initially-formed concentration of positive vorticity from the lower surface, preceded by the cluster of negative vorticity from the upper surface of the cylinder. This pattern is essentially inverted at N = 30. For the images shown in the right column, the initially-formed patterns of vorticity tend to be symmetrical and, together with the remaining vorticity concentrations in the flow, maintain a small value of C_y. Images at N = 20 in both the left and right columns correspond to motion of the cylinder in the same direction as the current; dispersed patterns of vorticity, arising from vortices formed during an earlier part of the cycle, exist on either side of the cylinder. The frequency f_e of the oscillation relative to the inherent Kármán f₀ frequency from a stationary cylinder is f_e/f_o= 1. The dimensionless amplitude is A/D = 0.955.