The Segré–Silberberg effect is a fluid dynamic separation effect where a dilute suspension of neutrally buoyant particles flowing (in laminar flow) in a tube equilibrates at a distance of 0.6R from the tube's centre.
This effect was first observed by Segré and Silberberg.
[1][2] The solid particles are subjected to both viscous drag forces and inertial lift forces.
The drag forces are responsible for driving particles along the flow streamlines, whereas the inertial forces are responsible for the lateral migration of particles across the flow streamlines.
The parabolic nature of the laminar velocity profile in Poiseuille flow produces a shear-induced inertial lift force that drives particles towards the channel walls.