Vortex (Air) : A cylindrical or conical shaped core of air or vapor lying along the central axis of the rotating slurry inside a hydrocyclone. (Bul 13C)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}