Abstract
The velocity distribution around a circular cylinder oscillated transversely in uniform flow was measured using an image measurement system. The external controllable VTR enables to obtain any image data on specified VTR frame, and automatic processing of image measurement. The conditional sampling and ensemble average are adopted to increase the spatio resolution.
The vortex shedding process under the lock-in phenomena was considered from the measured velocity and vorticity distribution. The anti-clockwise vortex shed at 0.42π<ωat<0.54π, and has small dissipation after the shedding.
