Abstract: A device for separating particles from a fluid suspension has a container supplied with fluid containing suspended particles. A plurality of parallel, planar first plates are spaced apart in a direction normal to the plates and are stationarily disposed within the container. Interspersed in the spaces between the first plates is a plurality of second parallel, planar plates movable with respect to the first plates in a circular path and operating to provide limited shearing forces in the fluid and substantially without eddy currents. A discharge pipe receives particles separated by gravity from the sheared fluid between the various plates. In a related form, the plates instead of being planar are circular-cylindrical, spaced apart, and are relatively rotated about a common axis.