Experiments on vortex funnel formation during drainage

We studied the vortex formation during drainage of water from a cylindrical vessel. The rate at which the vortex grows into a full funnel was found to depend on the initial velocity field characterized by Vθi, the maximum tangential velocity on the free surface and the nozzle location relative to the cylinder axis. We present a simple model to explain the observed results. This work provides important information especially for industrial process, for instance in steel continuous casting process.