The flow conditions must have a sufficiently small value of Reynolds number for there to be laminar flow.Īt 20 ☌, the dynamic viscosity (kinematic viscosity × density) of water is 1.0038 mPa The drag caused by relative motion of the fluid and a surface is a measure of the viscosity. In general, either the fluid remains stationary and an object moves through it, or the object is stationary and the fluid moves past it. Viscometers can measure only constant viscosity, that is, viscosity that does not change with flow conditions. Thus, a rheometer can be considered as a special type of viscometer.
For liquids with viscosities which vary with flow conditions, an instrument called a rheometer is used. Scientific instrument used to measure viscosityĪ viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid.
