conservation of the volume of the suspension equ4 in the above equations z r are axial and radial coordinates and u v are axial and radial components of the volume means suspension velocity c is the concentration of particles giving the volume of particles per unit volume of suspension finally u s and v s are the axial and radial components of the sedimentation velocity of the particles relative to the volume mean suspension velocity the equations 2 and 3 are combined with an expression for the driving force of gravity and the centrifugal effect the solution of the equations of motion for the two phase flow yields the following expression equ5 where equ6 and where equ7 u03bc e is the average viscosity of the red cell zone poise u03c1 e is the average density of the red cell zone g cm 3 y is the normal distance from the interior surface of the housing cm h f is the feed hematocrit the ratio of particle volume to blood volume q f is the volumetric feed rate cm 3 sec r is the normal distance to the centrifuge axis of rotation cm u03c1 p is the density of the plasma zone g cm 3 to use eq 4.