These can be assessed by monitoring power input, the decay time of oscillations, or changes in the resonated frequency. Viscosity can also be measured by applying oscillating vibrations to the sample and monitoring the damping effects of the fluid. Alternative viscometers only allow for single-point measurement and provide only shear viscosity measures. Using a rotational rheometer allows analysts to plot a full flow curve of the material’s flow characteristics in response to varying levels of shear force and determine more advanced material parameters. The amount of torque required to cause rotation across a horizontal plane in the sample is measured and is relative to sample viscosity. The time taken for the sample to travel through the capillary correlates to its kinematic viscosity.Ī rotational viscometer applies relatively weak levels of torque to a liquid sample to encourage mechanical deformation. This fluid is passed through a vertical U-tube of known dimensions and a very small diameter. Measuring viscosity via a capillary tube is one of the oldest methods of determining the kinematic viscosity of a sample, requiring prior knowledge of the density and volume of the sample of interest. This blog post will explore five of the fundamental measuring techniques for obtaining the dynamic viscosity and the kinematic viscosity of fluidic samples. This property is density-dependent and is measured in square meters per second (m 2/s). Kinematic viscosity refers to the resistive flow of a fluid under the influence of gravity.This characteristic is typically expressed in millipascal seconds (mPa-s).

Dynamic viscosity is a measure of the shear stress per unit area required before a sample begins to deform.Shear viscosity is expressed under two distinct forms: These Van der Waals forces are critical facets of a sample’s resistance to deformation, or flow, which defines the material’s viscosity. The viscous properties of a liquid or amorphous solid are primarily determined by inter-particle forces within the solution, including friction and attraction between molecules in the macrostructure.

Testing viscosity using glass plate