Experiments on flow around a cylinder; the velocity and vorticity fields

The flow field around a cylinder positioned normal to the flow in an open channel has been investigated experimentally for two types of flow. An Acoustic Doppler Velocity Profiler was used to obtain instantaneously the three directions of the velocity in the flow. Subsequently the vorticity of the flow field was calculated. Results of the experiments show that a horseshoe-vortex system is established, existing of a measurable vortex with underneath a return flow of negative vorticity. The system develops itself in the upstream corner at the nose of the cylinder and stretches around the cylinder towards the downstream.