Core-Annulus radial solids concentration distribution in riser

The radial particle concentration distribution in riser is comparatively low in the central area and increases sharply near the wall. It is the so-called typical core-annulus structure. The occurrence of the core-annulus was usually contributed to the velocity gradient in the boundary layer or the drag force. In this paper, an aerodynamic theory is used in the two-phase flow analysis. A transverse force on the particles, the Kutta-Joukowski force, is introduced to explain and quantify the formation of the core-annulus in riser. This force is the function of the particle velocity curl, the slip velocity and the gas density. Based on the experimental results combining with the data proposed in the published literatures, the distribution of the Kutta-Joukowski transverse force in riser is discussed. The results show that this force is the main factor of the core-annulus occurrence. (C) 2018 Published by Elsevier Ltd.