An air cavity above a complex vortex: an experimental and analytical study of the features of its lower part

The description of the experiments with the water vortex generated in a variety of facilities by means of different activators is presented. The changes in the form and size of the air cavity above such a vortex are studied for different regimes of rotations. An analytical description for the free surface form of the water vortex is given, which is in good agreement with both experimental data and previously obtained relations based on fundamental hydrodynamics equations. The problem of the "spout's" volume of the air cavity is also considered. It is shown that "spout's" volume can be used for calculating of the radius of the water "solid-state" rotation. Estimated calculations of the "spout's" volume based on experimental data are made. (paper)