Velocity measurements in the near wake of a freely-oscillating circular cylinder at lock-in

This chapter illustrates two component velocity measurements that are made with laser Doppler velocimetry in the base region and near wake of a freely vibrating, elastically mounted, and light weight circular cylinder at lock-in. Maximum cylinder displacements of 0.75 cylinder diameters are observed for a damping level of about 0.2% of critical. It is observed that the Scruton number is 1.5, while the Reynolds number at lock-in is about 53,000. The velocity data was phase averaged relative to the periodic loading cycle and is generally presented at cycle phase intervals. It is observed that the vortex formation process is similar to the one observed for stationary cylinders. Furthermore, the chapter reviews a possible physical explanation for the self-limiting oscillations that are based on the relative locations of the cylinder and the forming vortices.