Viscosity is perceived as 'thickness' or resistance to pouring, but there is more to viscosity than this. All fluids have an internal friction between molecules, which determines how well fluid flows. Due to this internal friction, energy is required to move the liquid and viscosity is the measure of the resistance to flow.
Viscosity Fluid Categorization
Fluids are categorized as Newtonian or non-Newtonian.
Newtonian fluids, such as water and some oils, are fluids that continue to flow at a given temperature, regardless of the forces acting on it. No matter how fast it is stirred or mixed, Newtonian fluids will always behave in the same manner. Newtonian fluids are generally measured with flow and dip viscosity cups.
Non-Newtonian fluids, such as paints and ketchup, are fluids which change viscosity when a force is applied. There are several different categories and sub-categories of non-Newtonian fluids, they can be described as the following:
Thixotropic - substances which are gel-like at rest but liquid when agitated, such as non-drip paints, tomato ketchup and most varieties of honey.
Rheopectic - substances where viscosity increases with duration of stress, such as some lubricants.
Pseudoplastics - also known as shear thinning - the viscosity decreases with increased shear rate, such as blood, gelatin and clay.
Dilatant - also known as shear thickening - the viscosity increases with increased shear rate, such as suspensions of rice, corn starch or concentrated sugar solution.
Viscosity is perceived as 'thickness' or resistance to pouring, but there is more to viscosity than this. All fluids have an internal friction between molecules, which determines how well fluid flows. Due to this internal friction, energy is required to move the liquid and viscosity is the measure of the resistance to flow.
Viscosity Fluid Categorization
Fluids are categorized as Newtonian or non-Newtonian.
Newtonian fluids, such as water and some oils, are fluids that continue to flow at a given temperature, regardless of the forces acting on it. No matter how fast it is stirred or mixed, Newtonian fluids will always behave in the same manner. Newtonian fluids are generally measured with flow and dip viscosity cups.
Non-Newtonian fluids, such as paints and ketchup, are fluids which change viscosity when a force is applied. There are several different categories and sub-categories of non-Newtonian fluids, they can be described as the following:
Thixotropic - substances which are gel-like at rest but liquid when agitated, such as non-drip paints, tomato ketchup and most varieties of honey.
Rheopectic - substances where viscosity increases with duration of stress, such as some lubricants.
Pseudoplastics - also known as shear thinning - the viscosity decreases with increased shear rate, such as blood, gelatin and clay.
Dilatant - also known as shear thickening - the viscosity increases with increased shear rate, such as suspensions of rice, corn starch or concentrated sugar solution.
