Classification of methods of viscosity measurement, absolute as well as relative, is
based on the geometry of flow.
Three main cases of flow are possible:
• flow of fluid between solid surfaces or through a hole in a solid body
• flow of fluid around a solid body
• free stream flow, relevant only to extension of a fluid stream.
Fluid flow between two solid surfaces can be realized in the following geometries:
• fluid flow through a capillary with cross-section of capillary being usually, but
not necessary, circular