TY JOUR TI MATHEMATICAL DESCRIPTION OF THE TWO-PHASE FLOW MOTION AT THE OUTLET OF THE VERTICAL ACCELERATION TUBE OF A JET MILL WITH A PLANE GRINDING CHAMBER OF TORUS FORM KW jet mill KW grinding chamber KW acceleration tube KW particle KW two-phase flow JO Bulletin of Belgorod State Technological University named after. V. G. Shukhov AU Dmitrienko, V.G. AU Voronov, V.P. AU Shemetov, E.G. AU Shemetova, O.M. PY 2021 IS 6 PB Belgorod State Technological University named after V.G. Shukhov