Oscillations of a vertical elastically-mounted cylinder in a wave

摘要: ( A bidirectional, vertical cylinder with a very low mass-damping parameter, m*~ = 0.0062, is immersed in sinusoidal free-surface wave. The undergoes oscillations that are sensitive to the frequency.ratio fr/fw, which fn natural . frequency of system water and fw At, vicinity of, fn/fw =2, trajectory achieves "butterfly" pattern. For this oscillation, unsteady flow field characterized using high-imagedensity particle image velocimetry. Instantaneous representations velocity vorticity patterns, interpreted simultaneously absolute relative velocities, provide insight into origin trajectories. Large-scale concentrations having substantial values circulation shed from surface when severe change direction on either left or right branch butterfly trajectory. Despite nearly symmetrical nature -left branches, generated by different means each two branches. These decay rapidly, however, a~ they separate surface. Certain as much diameters from, then later collide with, cylinder. Moreover, can migrate 180 around wben an abrupt at bottom its Finally, general observation, Karman-like shedding vortical structures occurs during those portions oscillation cycle becomes large.