To gain understanding of the two-phase vertical gas-solid flow behavio
ur, the equations of gas-solid suspension flow are used to develop a m
odel to predict the radial profiles of the volumetric fraction and the
velocity of the solid particles, We derived two coupled differential
equations for the volume fraction of the particles and the fluctuation
s of the particle velocity. These could be solved approximately, assum
ing the existence of a lean phase in the centre (the core) and a dense
particle phase near the wall (the annulus). In this boundary layer th
eory, the method of matched asymptotic expansions could be employed. A
s a result, the obtained expressions have a generic character and the
observed qualitative trends are insensitive with respect to the detail
ed modelling of the particle-turbulence and particle-particle interact
ions. (C) 1998 Elsevier Science B.V. All rights reserved.