The paper presents the model for formation of an axisymmetric vortex ring based on the viscous analogy to the Norbury vortices. By using the matching procedure suggested earlier and the obtained properties of the viscous vortex ring, it is found that when the limiting stroke value L/D ("formation number") reaches the value 4.0, the appropriate limiting values of the normalized energy and circulation become around 0.3 and 2.0, respectively. The predicted values are in agreement with the experimental data.

The World Congress "Aviation in the X X I-st Century", 14-16 september [Текст] = Матеріали Всесвітнього конгресу "Авіація ХХІ століття" 14-16 вересня 2003 року / International Civil Aviation Organization; Ministry of Education and Science of Ukraine; National Academy of Sciences of Ukraine; National Aviation University. — Kyiv : NAU, 2003. — 438 p. : il.