Cylinders undergoing one- and two-degree-of-freedom (DoF) motions were studied. Since the forces on the cylinder fluctuate in both the streamwise and transverse direction, it is believed that such motions are more natural than transverse-only vibrations. A set of experiments was conducted in a water tunnel using both digital particle image velocimetry (DPIV) and force measurements. Several qualitative differences were noted, including a dramatic increase in phase coherence and the disappearance of the "2P" mode. It appears that the transverse motion sets the frequency of shedding, and the streamwise motion the relative phase therein.
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