Therefore, extensional viscosity is a fundamental parameter in many industrial processes. Extensional viscosity is relevant when measuring any flow field involving a change in cross-sectional area. Relative viscosity is important when measuring viscosity of non-Newtonian fluids, specifically polymers - higher molar mass means higher viscosity in the polymer. Steady shear viscosity does not change when measuring Newtonian fluids, but is directly affected by shear rate of non-Newtonian fluids (Shear Thinning or Thickening or the deformation history for Thixotropic fluid). Kinematic viscosity has been the standard in oil industries. Dynamic viscosity is applicable when working to determine the effect that formulation changes have in regards of molecular interaction and viscosity, for example when formulation biopharmaceuticals. Because dynamic viscosity refers to resistance to flow, while kinematic viscosity relates that resistance to density, two fluids with the same dynamic viscosities can have very different kinematic viscosities depending on density and vice versa. So, we have the different viscosities defined, but what does it all really mean?ĭynamic viscosity will help you to interpret the interaction between molecules in terms of mechanical stress whereas kinematic viscosity is more convenient when working to determine fluid motion ad velocity field. Extensional viscosity - the resistance of a fluid to extensional flow (flow through a field involving a change in cross-sectional area).Relative viscosity – refers to the ratio of the viscosity of a solution to the viscosity of the solvent used.Steady shear (apparent) viscosity – refers to the relationship between viscosity and shear rate, more specifically the shear stress applied to a fluid divided by the shear rate.
Kinematic viscosity – refers to the ratio of dynamic viscosity to density, or a measurement of the viscosity of a fluid in motion.Dynamic (absolute) viscosity – the measurement of the fluid’s internal resistance to flow when force is applied.To determine the viscosity you should be measuring for your sample it’s important to first and foremost understand what the different types of viscosity are. Add on to the confusion the different types of viscosity – dynamic, kinematic, steady sheer, relative, extensional – and you may find yourself asking: “What is the difference and what type of viscosity should I be measuring?” While that seems straight forward, viscosity is complex and often confusing concept. Viscosity is a fluids resistance to flow.
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