Ultracentrifuges are a whole different animal than blood centrifuges. The former are used for separating tiny things like viruses, organelles, and macromolecule

Ultracentrifuges are a whole different animal than blood centrifuges. The former are used for separating tiny things like viruses, organelles, and macromolecules while the latter are used just to separate blood into white blood cell/platelet, red blood cell, and plasma layers. These cells are orders of magnitude larger than anything you'd use an ultracentrifuge for and short of deliberatly shaking the sample, it won't mix quickly after the centrifuge.