ABSTRACT
In the cgs (centimeter-gram-second) system in which the unit of force is dyne, the unit of viscosity is called a poise or centipoise (cp), in honor of Jean Poiseuille (1797-1869) who developed an improved method for measuring blood pressure. In the international System of Units (SI), the unit of force is newton (N) and the unit of viscosity is newton-second/square meter. One cp is 1 × 10−3Ns/m2. Finally, sometimes the viscosity is also given as the ratio of viscosity to the mass density of the fluid and is called the kinematic viscosity. That is, the kinematic viscosity is given by
ν = µ/ρ,
where ρ is the fluid mass density (mass per unit volume). The unit of ν is in m2/s or cm2/s. In Table 8.1 some experimental viscosity data are given for some gases and liquids at one atm pressure [6]. Note that at room temperature the viscosity is about one cp for water and about 0.02 cp for air.
