The Segrè–Silberberg effect is a
fluid dynamic
In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in motio ...
separation effect where a dilute suspension of neutrally buoyant particles flowing (in
laminar flow
Laminar flow () is the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral m ...
) in a tube equilibrates at a distance of 0.6''R'' from the tube's centre. This effect was first observed by
Gino Segrè
Gino Claudio Segrè (born October 4, 1938) is an Italian-American physicist, Professor of Physics Emeritus at the University of Pennsylvania. He is the author of several books on the history of science, particularly on atomic physics. Segrè's ' ...
and Alexander Silberberg in 1961.
The solid particles are subjected to both viscous
drag forces and
inertial
In classical physics and special relativity, an inertial frame of reference (also called an inertial space or a Galilean reference frame) is a frame of reference in which objects exhibit inertia: they remain at rest or in uniform motion relative ...
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. As particles migrate closer to the channel walls, the flow around the particle induces a pressure increase between the particle and the wall which prevents particles of moving closer.
The opposing lift forces are dependent on the particle diameter to channel diameter
ratio (
), and dominate for
.
References
{{DEFAULTSORT:Segre-Silberberg effect
Fluid dynamics