a b s t r a c t
This paper investigates the hydrodynamic behavior of gas–solid two-phase flowin the annular space of an air drilling
well under different arrangements by using three-dimensional approach. Two-fluid model is used to solve the governing
equations in the Eulerian–Eulerian framework. Effect of eccentricity and drill pipe rotation on the pressure
drop, volume fraction and velocity profile are examined. The results are compared with available data in the literature
and good agreement is found. The results show that the presence of solid particles in the annulus change the air
velocity profile significantly and create two off-center peaks velocity close to the walls instead of one peak velocity
in the middle. Eccentricity of drill pipe makes more accumulation of the cuttings in the smaller space of the annulus.
Increasing the eccentricity increases pressure drop due to impact of particles with annulus wall and also particles
collision with each other. Rotation of the drill pipe shifts maximum air velocity location toward smaller space of the
annulus which results more uniform cutting distributions in the annulus and improvement in their transportations.
Pressure drop in the annulus increases as eccentricity and rotation of drill pipe increase.
Keywords: Gas–solid; Two-phase flow; Air drilling; Annulus