Sedimentation of two spheres in a square tube

In this study, we simulated the sedimentation of two identical spheres having the same density in a square tube. Compared with the center-line and the diagonal planes (including the reverse diagonal plane), the sedimentation of spheres on other planes is more complicated. Results show that at relatively low and high Reynolds number, the spheres will deflect and eventually move to the diagonal plane of the square tube. At the medium Reynolds number, the spheres settle near the initial plane. The possible mechanisms underlying these behaviors are examined. Finally, it is shown that the distance between the spheres increases with an increase in the Reynolds number, which is applicable to all the initial settlement planes studied.