Friction friction and wear in so-called self-lubricating materials. Fluid friction occurs between fluid layers that are moving relative to each other. This internal resistance to flow is named "viscosity". In everyday terms, the viscosity of a fluid is described as its "thickness". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity. The less viscous the fluid, the greater its ease of deformation or movement. All real fluids (except superfluids) offer some resistance to shearing and therefore are viscous. For teaching and explanatory purposes it is helpful to use the concept of an inviscid fluid
Flow focusing seeded in hydrodynamic focussing which has been in existence since 1963, as was developed by flow cytometry scientist. The basic principle consists of a continuous phase fluid (focusing or sheath fluid) flanking or surrounding the dispersed phase (focused or core fluid), so as to give rise to droplet or bubble break-off in the vicinity of an orifice through which both fluids are extruded. The principle may be extended to two or more coaxial fluids; gases and liquids may be combined; and, depending of the geometry of the feed tube and orifices, the flow pattern may be cylindrical or planar. Both