A material requiring a shear stress of one dyne per square centimeter to produce a shear rate of. Many chemists still use an old unit of viscosity, the poise (P), named after the French physician Jean Poiseuille. The fundamental unit of viscosity measurement is the poise. s"^"-1"#, then the fluid has a viscosity #eta = "1 Pa.One poiseuille is 10 poise or 1000 cP, while 1 cP 1 mPa·s (one millipascal-second). It is sometimes referred to as the poiseuille (Pl). If a fluid is placed between two #"1 m"^2# plates that are 1 m apart and one plate is pushed sideways with a force of 1 N and it moves at a velocity of #1color(white)(l) "m Kinematic viscosity is the ratio of dynamic viscosity to density of the fluid.The SI unit of the quantity is square meter per second (symbol m/s). This is the SI unit of viscosity, equivalent to newton-second per square metre (N·s m2). Thus, the units of viscosity are #("N" × color(red)(cancel(color(black)("m"))))/("m"^2 × color(red)(cancel(color(black)("m")))
In terms of the above diagram, the formula for viscosity #eta# is One way to measure viscosity is to place the fluid between two flat parallel plates and slide one plate past the other. We usually think of the viscosity of a liquid as its "thickness".įor example, we say that honey is "thicker" (has a higher viscosity) than water. America, and the milliPascal-second (mPa-s) in other countries, although there is some degree of overlap in useage. In SI system of units, viscosities are expressed in N s/m 2 or (Pa s) and kinematic viscosities in either m 2 /s or cm 2 /s. The viscosity of a fluid is a measure of its resistance to flow. The unit of measurement used to quantify rotational viscosity is the centipoise (cP) in N. Poise, Centipoise, Pound force-Second/square Inch, Poundal-Second/square Foot, Gram/Centimeter-Second, Slug/Foot-Second, Pound/Foot-Second and more. For example, if viscosity is in poise, and the density in grams per cubic centimeter, the unit of kinematic viscosity is the stoke, having the unit square centimeters per second (cm 2 /s).